EFFECTIVENESS OF CALCIUM CARBIDE FOR IMPROVING NUTRIENT USE EFFICIENCY AND

YIELD OF WHEAT CROP

By

RASHID MAHMOOD M.Sc. (Hons) Agri.

A thesis submitted in partial fulfillment of the requirements for the degree of

DOCTOR OF PHYLOSOPHY

IN

SOIL & ENVIRONMENTAL SCIENCES

INSTITUE OF SOIL & ENVIRONMENTAL SCIENCES UNIVERSITY OF AGRICULTURE, FAISALABAD

PAKISTAN 2009

To

The Controller of Examination, University of Agriculture, Faisalabad. We, Supervisory Committee, certify that the contents and form of thesis

submitted by Mr. Rashid Mahmood (Regd. No. 97-ag-1129) have been found

satisfactory and recommend that it be processed for evaluation by the External

Examiner(s) for the award of degree.

SUPERVISORY COMMITTEE 1) CHAIRMAN :

(DR. MUHAMMAD YASEEN) 2) MEMBER :

(DR. MUHAMMAD ARSHAD) 3) MEMBER :

(DR. ASIF TANVEER)

i

ACKNOLEDGEMENT

All admirations and thanks are for stupendous Allah, the Omnipotent, the

Sublime, Only Creator of the universe and the source of knowledge and ingenuity Who

benedict me with health, thoughts, talented teachers, helping friends and opportunity to

complete this study. I offer my meekly thanks to Holy prophet (peace be upon him) the

nimbus, the beacon, whose moral and spiritual teachings illuminate my heart, mind, and

thrived my thoughts towards achieving high ideas of life.

I feel highly privileged to express my heartiest gratitude to my honorable

supervisor Dr. Muhammad Yaseen, Associate Professor Institute of Soil and

Environmental Sciences, University of Agriculture Faisalabad, for his keen interest, full

help, valuable suggestions, timely advice and sympathetic attitude throughout the study.

With deep sense of honor, I wish to extend my sincere gratitude to Dr.

Muhammad Arshad (T.I.), Professor, Institute of Soil and Environmental Sciences for

his inspiring help and sympathetic guidance throughout the research period. Special

thanks are extended to Dr. Asif Tanveer, Professor, Department of Agronomy, for his

part as a member of supervisory committee.

My gratitude will remain incomplete if I do not mention the contribution and

corporation of my sincere friends, Dr. Saif Ur Rehman Kashif and Mr. Muhammad

Usman and farmer Mr. Nasir Mahmood in completing my research work.

No acknowledgement could ever adequately express my obligations to my

affectionate father, Muhammad Younas and Sweet Loving Mother whose hands

always raised in prayers for me and with out whose moral and financial support, the

present distinction would merely be a dream.

I express my heartiest and sincere sense of gratitude to my wife for her prayers

and moral help during the write up of thesis.

Special love for my kids (Amer Hamza, Muhammad Ibrahein and Moaz

Ahmad) for long wait during my studies.

RASHID MAHMOOD

ii

TABLE OF CONTENTS

CHAPTER NO. TITLE PAGE ABSTRACT 1 CHAPTER 1 INTRODUCTION 2 CHAPTER 2 REVIEW OF LITERATURE 7 2.1 Nitrogen use efficiency 7 2.2 Type of nitrogen nutrition for crop plants 9 2.3 Nitrification inhibitors 10 2.4 Calcium carbide as a nitrification inhibitor 11 2.5 Comparison of ECC with other nitrification inhibitors 12 2.6 Role of ethylene in crop production 13 2.7 Effect of calcium carbide on growth and yield of crops 18 CHAPTER 3 MATERIALS AND METHODS 21 3.1 Experiment 1: Effect of Rate of Encapsulated Calcium

Carbide on Growth, Yield and Nitrogen Uptake of Wheat (Pot Trial)

21

3.1.1 Site of experiment 21 3.1.2 Soil preparation 21 3.1.3 Soil analysis 22 3.1.3.1 Mechanical analysis 22 3.1.3.2 Saturation percentage 22 3.1.3.3 pH of saturated soil paste (pHs) 22 3.1.3.4 Electrical conductivity of saturated soil extract (ECe) 22 3.1.3.5 Carbonates and bicarbonates 23 3.1.3.6 Chlorides 23 3.1.3.7 Sulphate 23 3.1.3.8 Sodium and potassium 23 3.1.3.9 Calcium and magnesium 23 3.1.3.10 Cation exchange capacity (CEC) 23 3.1.3.11 Organic matter 23 3.1.3.12 Total nitrogen 24 3.1.3.13 Available phosphorus 24 3.1.3.14 Available potassium 24 3.1.4 Pot filling 24 3.1.5 Layout of experiment 24 3.1.6 Encapsulation of calcium carbide 26 3.1.7 Treatment plan 26 3.1.8 Parameters studied 27

iii

3.1.8.1 Plant height 27 3.1.8.2 Number of total and fertile tillers pot-1 27 3.1.8.3 Root weight 27 3.1.8.4 Biological yield 27 3.1.8.5 Grain yield 27 3.1.8.6 Straw yield 27 3.1.8.7 Nitrogen concentration in different plant parts 27 3.1.8.8 Nitrogen uptake by straw or grain 28

3.2 Experiment 2: Effect of Time of Application of Encapsulated Calcium Carbide on Growth, Yield and Nitrogen Uptake of Wheat (Pot Trial)

28

3.2.1 Site of experiment 28 3.2.2 Soil preparation 28 3.2.3 Soil analysis 28 3.2.4 Pot filling 28 3.2.5 Layout of experiment 28 3.2.6 Encapsulation of calcium carbide 28 3.2.7 Treatment plan 28 3.2.8 Parameters studied 29 3.3 Experiment 3: Evaluation of Different Type of Calcium

Carbide Based Formulations for the Release of Acetylene and Ethylene Gases and Their Effect on Nitrification Inhibition under Laboratory Conditions

29

3.3.1 Preparation of calcium carbide (CaC2) formulations 29 3.3.1.1 Grinding and sieving of calcium carbide 29 3.3.1.2 Encapsulation of calcium carbide 30 3.3.1.3 Bee-wax coating 30 3.3.1.4 Paraffin-wax coating 31 3.3.1.5 Paint coating 31 3.3.1.6 Matrices formation 31 3.3.2 Soil preparation 32 3.3.3 Fertilizer application 32 3.3.4 Bottle filling 32 3.3.5 Treatment plan 32 3.3.6 Incubation conditions 33 3.3.7 Moisture maintenance 33 3.3.8 Gas sampling 33 3.3.9 Analysis for acetylene and ethylene contents 33 3.3.10 Acetylene and ethylene flux 34 3.3.11 Soil sampling 34 3.3.12 Soil analysis for nitrate-N and ammonium-N

concentrations 34

iv

3.4 Experiment 4: 34 3.4.1 Experiment 4(A): Effect of Calcium Carbide Based

Formulations on Seed Germination, Seedling Growth and Root : Shoot Ratio of Wheat (Laboratory Study)

35

3.4.1.1 Seed sowing 35 3.4.1.2 Treatment plan 35 3.4.1.3 Experimental design 35 3.4.1.4 Calculation of mean emergence time and emergence

rate index 36

3.4.1.5 Fresh biomass weight determination 36 3.4.1.6 Root : shoot ratios 36 3.4.2 Experiment 4(B): Effect of Rate of Calcium Carbide

(Matrix-I) on Wheat Seedling Emergence (Pot Trial) 37

3.4.2.1 Seed sowing 37 3.4.2.2 Calcium carbide application 37 3.4.2.3 Mean emergence time and emergence rate index 37 3.5 Experiment 5: Effect of Calcium Carbide Based

Formulations on Growth, Yield and Nitrogen Uptake of Wheat (Pot Trial)

37

3.5.1 Treatment plan 38 3.5.2 Parameters studied 38 3.5.2.1 Thousand grains weight 38 3.5.2.2 Soil mineral nitrogen 38 3.6 Experiment 6: Effect of Rate and Application Depth of

Matrix-I (Calcium Carbide Based Formulation) on Growth Yield and Nitrogen Uptake of Wheat (Pot Trial)

39

3.6.1 Treatment plan 39 3.6.1.1 Rate of application of calcium carbide (Factor A) 39 3.6.1.2 Depth of application of calcium carbide (Factor B) 39 3.7.2 Parameter studied 39 3.7 Experiment 7: Response of Wheat to Soil Applied

Calcium Carbide (Matrix-I) with and without Nitrogen Fertilizer (Pot Trial)

40

3.7.1 Treatment Plan 40 3.7.1.1 Rate of N fertilizer application (FactorA) 40 3.7.1.2 Rate of calcium carbide application (Factor B) 40 3.7.2 Parameter studied 40 3.7.2.1 Spike length 41 3.7.2.2 Number of spikelets spike-1 41 3.7.2.3 Number of grains spike-1 41

v

3.8 Experiment 8: Growth and Yield Response of Wheat to

Soil Applied Calcium Carbide under Field Conditions 41

3.8.1 Type of experiment 41 3.8.2 Date of sowing and harvesting of wheat crop 41 3.8.3 Treatment plan 41 3.8.4 Soil physical and chemical analysis 42 3.8.5 Fertilizer application 42 3.8.6 Calcium carbide application 42 3.8.7 Parameters studied 42 3.8.7.1 Plant height 42 3.8.7.2 Number of tillers and spikes 42 3.8.7.3 Biological yield and grain yield 45 3.8.7.4 Lodging index 45 3.8.7.5 Soil mineral nitrogen 45 3.9.7.6 Other parameters 45 3.9 Statistical analysis 45 CHAPTER 4 RESULTS AND DISCUSSION 46 4.1 Experiment 1: Effect of Rate of Encapsulated Calcium

Carbide on Growth, Yield and Nitrogen Uptake of Wheat (Pot Trial)

46

4.1.1 Introduction 46 4.1.2 Materials and Methods 47 4.1.3 Results and Discussion 47 4.1.3.1 Results 47 4.1.3.1.1 Plant height 47 4.1.3.1.2 Number of tiller pot-1 48 4.1.3.1.3 Root weight 48 4.1.3.1.4 Straw yield 48 4.1.3.1.5 Grain yield 52 4.1.3.1.6 Total nitrogen uptake 52 4.1.3.2 Discussion 52 4.2 Experiment 2: Effect of Time of Application of

Encapsulated Calcium Carbide on Growth, Yield and Nitrogen Uptake of Wheat (Pot Trial)

55

4.2.1 Introduction 55 4.2.2 Materials and Methods 55 4.2.3 Results and discussion 55 4.2.3.1 Results 55 4.2.3.1.1 Plant height 56 4.2.3.1.2 Number of tillers pot-1 56 4.2.3.1.3 Root weight 56

vi

4.2.3.1.4 Straw yield 56 4.2.3.1.5 Grain yield 59 4.2.3.1.6 Total nitrogen uptake 59 4.2.3.2 Discussion 59 4.3 Experiment 3: Evaluation of Different Types of

Calcium Carbide Based Formulations for the Release of Acetylene and Ethylene Gases and Their Effect on Nitrification Inhibition under Laboratory Conditions

62

4.3.1 Introduction 62 4.3.2 Materials and Methods 63 4.3.3 Results and Discussion 63 4.3.3.1 Results 63 4.3.3.1.1 Release of acetylene gas from calcium carbide based

formulation amended soil 63

4.3.3.1.2 Release of ethylene gas from calcium carbide based formulation amended soil

64

4.3.3.1.3 Acetylene and ethylene flux 64 4.3.3.1.4 Concentration of Ammonium-nitrogen in formulated

calcium carbide amended soil 67

4.3.3.1.5 Concentration of Nitrate-nitrogen in formulated calcium carbide amended soil

67

4.3.3.2 Discussion 69 4.4.1 Experiment 4(A): Effect of Calcium Carbide Based

Formulations on Seed Germination, Seedling Growth and Root : Shoot Ratio of Wheat (Laboratory Study)

71

4.4.1.1 Introduction 71 4.4.1.2 Materials and Methods 72 4.4.1.3 Results and Discussion 72 4.4.1.3.1 Results 72 4.4.1.3.1.1 Mean emergence time 72 4.4.1.3.1.2 Emergence rate index 72 4.4.1.3.1.3 Fresh biomass weight 73 4.4.1.3.1.4 Root and shoot length 77 4.4.1.3.1.5 Root and shoot weight 77 4.4.1.3.1.6 Root : shoot ratios 77 4.4.1.4.2 Discussion 81 4.4.2 Experiment 4(B): Effect of Different Doses of Matrix-I

Based Calcium Carbide on Wheat Seedling Emergence (Pot Trial)

82

4.4.2.1 Introduction 83 4.4.2.2 Materials and Methods 83 4.4.2.3 Results and Discussion 83 4.4.2.3.1 Results 83

vii

4.4.2.3.1.1 Mean emergence time 83 4.4.2.3.1.2 Emergence rate index 84 4.4.2.3.2 Discussion 84 4.5 Experiment 5: Effect of Calcium Carbide Based

Formulations on Growth, Yield and Nitrogen Uptake of Wheat (Pot Trial)

86

4.5.1 Introduction 86 4.5.2 Materials and Methods 86 4.5.3 Results and Discussion 87 4.5.3.1 Results 87 4.5.3.1.1 Plant height 87 4.5.3.1.2 Number of tillers pot-1 87 4.5.3.1.3 Root weight 87 4.5.3.1.4 Thousand grains weight 89 4.5.3.1.5 Biological yield 89 4.5.3.1.6 Grain yield 89 4.5.3.1.7 Nitrogen concentration in different plant parts of wheat 92 4.5.3.1.8 N uptake by different plant parts of wheat 92 4.5.3.1.9 Soil mineral nitrogen content 97 4.5.3.2 Discussion 97 4.6 Experiment 6: Effect of Rate and Application Depth of

Matrix-I Calcium Carbide Based Formulation on Growth Yield and Nitrogen Uptake of Wheat (Pot Trial)

101

4.6.1 Introduction 101 4.6.2 Materials and Methods 101 4.6.3 Results and Discussion 101 4.6.3.1 Results 102 4.6.3.1.1 Plant height 102 4.6.3.1.2 Number of tillers pot-1 102 4.6.3.1.3 Thousand grains weight 104 4.6.3.1.4 Biological yield 104 4.6.3.1.5 Grain yield 104 4.6.3.1.6 Nitrogen concentration in wheat straw and grains 106 4.6.3.1.7 Nitrogen uptake by wheat straw and grains 106 4.6.3.2 Discussion 106 4.7 Experiment 7: Response of Wheat to Soil Applied

Matrix-I Formulated Calcium Carbide with and without Nitrogen Fertilizer (Pot Trial)

109

4.7.1 Introduction 109 4.7.2 Materials and Methods 110 4.7.3 Results and Discussion 110 4.7.3.1 Results 110 4.7.3.1.1 Plant height 110

viii

4.7.3.1.2 Number of tillers 110 4.7.3.1.3 Spike length 112 4.7.3.1.4 Number of spikelets 112 4.7.3.1.5 Number of grains 114 4.7.3.1.6 Thousand grains weight 114 4.7.3.1.7 Biological yield 114 4.7.3.1.8 Grain yield 117 4.7.3.1.9 Nitrogen concentration in wheat straw and grains 117 4.7.3.1.10 Nitrogen uptake by wheat straw and grains 117 4.7.3.1.11 Relative percent increase in parameters 120 4.7.3.1.12 Nitrogen use efficiency 120 4.7.3.2 Discussion 120 4.8 Experiment 8:Growth and Yield Response of Wheat to

Soil Applied Calcium Carbide under Field Conditions 123

4.8.1 Introduction 123 4.8.2 Materials and Methods 124 4.8.3 Results and Discussion 124 4.8.3.1 Results 124 4.8.3.1.1 Plant height 124 4.8.3.1.2 Number of tillers 124 4.8.3.1.3 Thousand-grains weight 128 4.8.3.1.4 Biological yield 128 4.8.3.1.5 Straw yield 128 4.8.3.1.6 Grain yield 132 4.8.3.1.7 Lodging index 132 4.8.3.1.8 Nitrogen concentration in wheat straw and grains 136 4.8.3.1.9 Nitrogen uptake by wheat straw and grains 136 4.8.3.1.10 Nitrate-N concentration in soil 141 4.8.3.1.11 Ammonium-N concentration in soil 141 4.8.3.2 Discussion 141 CHAPTER 5 SUMMARY 145 LITERATURE CITED 150 ANNEXURES FOR STATISTICAL ANALYSIS 167

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LIST OF TABLES

TABLE TITLE PAGE Table 3.1 Physico-chemical characteristics of soil for laboratory and

pot trials. 25

Table 3.2 Layout plan of experiment 8. 43 Table 3.3 Physico-chemical characteristics of farmer field soil at

Toba Tek Singh. 44

Table 6.1 Effect of rate and application depth of calcium carbide (matrix-I) on plant height (cm) of wheat.

103

Table 6.2 Effect of rate and application depth of calcium carbide (matrix-I) on total number of tillers pot-1 of wheat.

103

Table 6.3 Effect of rate and application depth of calcium carbide (matrix-I) on number of fertile tillers pot-1 of wheat.

103

Table 6.4 Effect of rate and application depth of calcium carbide (matrix-I) on number of unfertile tillers pot-1 of wheat.

103

Table 6.5 Effect of rate and application depth of calcium carbide (matrix-I) on 1000-grains weight (g) of wheat.

105

Table 6.6 Effect of rate and application depth of calcium carbide (matrix-I) on biological yield (g pot-1) of wheat.

105

Table 6.7 Effect of rate and application depth of calcium carbide (matrix-I) on grain yield (g pot-1) of wheat.

105

Table 6.8 Effect of rate and application depth of calcium carbide (matrix-I) on nitrogen concentration (%) in wheat straw.

107

Table 6.9 Effect of rate and application depth of calcium carbide (matrix-I) on nitrogen concentration (%) in wheat grain.

107

Table 6.10 Effect of rate and application depth of calcium carbide (matrix-I) on nitrogen uptake (g pot-1) by wheat straw.

107

Table 6.11 Effect of rate and application depth of calcium carbide (matrix-I) on nitrogen uptake (g pot-1) by wheat grain.

107

Table 7.1 Effect of different rates of matrix-I formulated calcium carbide with and without nitrogen fertilizer on nitrogen concentration and uptake by wheat straw and grain.

119

Table 7.2 Relative percent increase/decrease in growth and yield parameters and nitrogen status of wheat plant due to calcium carbide application compared to respective treatment of fertilizer alone.

121

Table 7.3 Effect of rate of matrix-I formulated calcium carbide with half and full recommended dose of N fertilizer on different efficiency parameters of wheat.

121

Table 8.1 Lodging response of two wheat cultivars to applied calcium carbide.

135

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LIST OF FIGURES

FIGURE TITLE PAGE Fig. 3.1 Encapsulation of calcium carbide. 26 Fig. 3.2 (a) Mechanical hammer, (b) Fine grinder and (c)

mechanical sieve. 30

Fig. 3.3 Inner Surface of Drum. 30 Fig. 3.4 Wax coated CaC2. 31 Fig.3.5 Matrix-I. 31 Fig.3.6 Experimental bottle with rubber septum. 32 Fig. 4.1 Effect of rate of encapsulated calcium carbide on plant

height of wheat. 49

Fig. 4.2 Effect of rate of encapsulated calcium carbide on number of tillers pot-1 of wheat.

49

Fig. 4.3 Wheat growth pattern in response to encapsulated calcium carbide application (a) NPK alone (b) NPK plus ECC @ 22.5 mg kg-1 soil.

50

Fig. 4.4 Effect of rate of encapsulated calcium carbide on root weight of wheat.

51

Fig.4.5 Effect of rate of encapsulated calcium carbide on straw yield of wheat.

51

Fig.4.6 Effect of rate of encapsulated calcium carbide on grain yield of wheat.

53

Fig.4.7 Effect of rate of encapsulated calcium carbide on nitrogen uptake by wheat tops at maturity.

53

Fig.4.8 Effect of time of application of encapsulated calcium carbide on plant height of wheat.

57

Fig.4.9 Effect of time of application of encapsulated calcium carbide on number of tillers pot-1 of wheat.

57

Fig.4.10 Effect of time of application of encapsulated calcium carbide on root weight of wheat.

58

Fig.4.11 Effect of time of application of encapsulated calcium carbide on straw yield of wheat.

58

Fig.4.12 Effect of time of application of encapsulated calcium carbide on grain yield of wheat.

60

Fig.4.13 Effect of time of application of encapsulated calcium carbide on total N uptake of wheat.

60

Fig.4.14 Effect of calcium carbide based formulations on the release of (a) acetylene (b) ethylene content in the soil.

65

Fig.4.15 Effect of calcium carbide based formulations on (a) acetylene (b) ethylene flux from the soil surface.

66

Fig.4.16 Effect of calcium carbide based formulations on soil (a) ammonium-N (b) nitrate-N content at different time intervals.

68

xi

Fig.4.17 Effect of calcium carbide based formulations on (a) mean emergence time (b) emergence rate index of wheat seedlings.

74

Fig.4.18 Effect of calcium carbide based formulations on fresh biomass weight of wheat seedlings 3, 6, 12 and 15 days after sowing.

75

Fig.4.19 Effect of calcium carbide based formulations on wheat seedling growth 3 days after sowing.

76

Fig.4.20 Effect of calcium carbide based formulations on root and shoot (a) length (b) weight of wheat seedlings 15 days after sowing.

78

Fig.4.21 Effect of calcium carbide based formulations on wheat root growth 15 days after sowing.

79

Fig.4.22 Effect of calcium carbide based formulations on root : shoot ratios by length and weight of wheat seedlings 15 days after sowing.

80

Fig.4.23 Effect of different doses of matrix-I based calcium carbide on (a) mean emergence time (b) emergence rate index of wheat seedlings.

85

Fig.5.1 Effect of calcium carbide based formulations on plant height of wheat.

88

Fig.5.2 Effect of calcium carbide based formulations on number of tillers pot-1 of wheat.

88

Fig.5.3 Effect of calcium carbide based formulations on root weight of wheat.

90

Fig.5.4 Effect of calcium carbide based formulations on 1000-grains weight of wheat.

90

Fig.5.5 Effect of calcium carbide based formulations on (a) biological yield (b) grain yield of wheat.

91

Fig.5.6 Effect of calcium carbide based formulations on N concentration in wheat (a) root (b) straw and (c) grain.

93-94

Fig.5.7 Effect of calcium carbide based formulations on N uptake by wheat (a) root (b) straw and (c) grain.

95-96

Fig.5.8 Effect of calcium carbide based formulations on total N uptake by wheat.

98

Fig.5.9 Effect of calcium carbide based formulations on N partitioning in different plant parts of wheat at maturity.

98

Fig. 5.10 Effect of calcium carbide based formulations on soil mineral nitrogen after 8 weeks of calcium carbide application.

99

Fig.7.1 Effect of different rates of matrix-I formulated calcium carbide with and without N fertilizer on plant height of wheat.

111

Fig.7.2 Effect of different rates of matrix-I formulated calcium carbide with and without N fertilizer on total number of tillers of wheat.

111

xii

Fig.7.3 Effect of different rates of matrix-I formulated calcium carbide with and without N fertilizer on number of fertile tillers of wheat.

113

Fig.7.4 Effect of different rates of matrix-I formulated calcium carbide with and without N fertilizer on spike length of wheat.

113

Fig.7.5 Effect of different rates of matrix-I formulated calcium carbide with and without N fertilizer on number of spikelets spike-1 of wheat.

115

Fig.7.6 Effect of rate of matrix-I formulated calcium carbide with and without N fertilizer on number of grains spike-1 of wheat.

115

Fig.7.7 Effect of different rates of matrix-I formulated calcium carbide with and without N fertilizer on 1000-grains weight of wheat.

116

Fig.7.8 Effect of rate of matrix-I formulated calcium carbide with and without N fertilizer on biological yield of wheat.

116

Fig.7.9 Effect of different rates of matrix-I formulated calcium carbide with and without N fertilizer on grain yield of wheat.

118

Fig.8.1 Effect of different rates and type of calcium carbide based formulations on plant height of two wheat cultivars under field conditions.

125

Fig.8.2 Effect of different rates and type of calcium carbide based formulations on number of tillers of two wheat cultivars under field conditions.

126

Fig.8.3 Effect of different rates and type of calcium carbide based formulations on number of spikes of two wheat cultivars under field conditions.

127

Fig.8.4 Effect of different rates and type of calcium carbide based formulations on 1000-grains weight of two wheat cultivars under field conditions.

129

Fig.8.5 Effect of different rates and type of calcium carbide based formulations on biological yield of two wheat cultivars under field conditions.

130

Fig.8.6 Effect of different rates and type of calcium carbide based formulations on straw yield of two wheat cultivars under field conditions.

131

Fig.8.7 Effect of different rates and type of calcium carbide based formulations on grain yield of two wheat cultivars under field conditions.

133

Fig.8.8 Effect of different rates and type of calcium carbide based formulations on lodging index of two wheat cultivars under field conditions.

134

Fig.8.9 Effect of different rates and type of calcium carbide based formulations on N concentration in straw of two wheat

137

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cultivars under field conditions. Fig.8.10 Effect of different rates and type of calcium carbide based

formulations on N concentration in grain of two wheat cultivars under field conditions.

138

Fig.8.11 Effect of different rates and type of calcium carbide based formulations on N uptake by straw of two wheat cultivars under field conditions.

139

Fig.8.12 Effect of different rates and type of calcium carbide based formulations on N uptake by grain of two wheat cultivars under field conditions.

140

Fig.8.13 Effect of different rates and type of calcium carbide based formulations on soil nitrate-N determined after 8 weeks of CaC2 application under field conditions.

142

Fig.8.14 Effect of different rates and type of calcium carbide based formulations on soil ammonium-N determined after 8 weeks of CaC2 application under field conditions.

142

LIST OF ANNEXURES

ANNEXURE TITLE PAGEAnnexure I Analysis of Variance and LSD test of exp. 1 167 Annexure II Analysis of Variance and LSD test of exp. 2 169 Annexure III Analysis of Variance and LSD test of exp. 3 171 Annexure IV(A) Analysis of Variance and LSD test of exp. 4(A) 175 Annexure IV(B) Analysis of Variance and LSD e test of exp. 4(B) 179 Annexure V Analysis of Variance and LSD test of exp. 5 180 Annexure VI Analysis of Variance exp. 6 186 Annexure VII Analysis of Variance and LSD test of exp. 7 190 Annexure VIII Analysis of Variance and LSD test of exp. 8 197

1

ABSTRACT Calcium carbide is well known as a nitrification inhibitor and its role as a source of ethylene (C2H4), a potent plant growth regulator, is not thoroughly investigated. Laboratory, pot and field studies were conducted, in a sequence, up to 4 years to evaluate the effectiveness of calcium carbide (CaC2) on nitrogen use efficiency, growth and yield of wheat. First and 2nd experiments were conducted to assess the best rate and time of application of encapsulated calcium carbide (ECC) regarding plant growth and yield parameters of wheat. It was found that ECC @ 22.5 mg kg-1 soil, applied 2 weeks after sowing performed the best of all other rates and times of application of ECC in improving economical yield of wheat. In the 3rd experiment CaC2 coated with bee wax, paraffin wax and black enamel paint and matrices (prepared with polyethylene) was used to slow release the gases. Release of acetylene and ethylene from these calcium carbide based formulations and their impact on nitrification process in the soil environment under laboratory conditions was studied. It was noted that matrix-I (containing 21 % CaC2) not only performed as the best and sustainable source of acetylene and ethylene in the soil but also inhibited nitrification process better than other formulations. Calcium carbide based formulations were also compared in pot studies regarding their effect on wheat seed germination and growth and yield parameters of wheat. Matrix-I benefited the wheat crop to the maximum, followed by matrix-II and paint coated calcium carbide. Two further pot experiments were conducted to know the best rate and application depth of matrix-I formulated calcium carbide with and with out nitrogen fertilizer application. It is evident from the results that matrix-I not only improved growth and yield parameters of wheat but also enhanced N uptake by different plant parts of wheat when applied @ 15 mg CaC2 kg-1 soil at 8 cm soil depth. It was further noted that matrix-I better improved N use efficiency when applied with half recommended dose of N fertilizer than that of with full recommended N fertilizer rate. Two years field experimentation confirmed the results of pot studies. Under field condition CaC2 based formulations not only improved wheat growth and yield parameters but also reduced lodging of a lodging susceptible wheat variety Bhakhar-2002. Overall results suggest that application of calcium carbide increased grain yield more than 30 % by improving yield contributing factors and N use efficiency.

2

CHAPTER 1 INTRODUCTION

Unmanaged, over and ever increasing human population has swallowed rich

agriculture lands. Areas around towns and big cities, which were fertile and cultivated a

decade ago, has replaced now by housing schemes and factory works. Compared with the

past, today we have more mouths to feed and more bodies to dress but no more land for

the cultivation of arable crops. This situation forces us to increase per unit area

production of major crops like wheat, rice, cotton, maize and sugarcane etc.

Wheat (Triticum aestivum L.) is one of the premier food crops and staple food of

majority population of Pakistan. Wheat flour is used to make bread and bakery products

and its bran and straw as cattle feed. In Pakistan wheat is cultivated on an area of 8.4 mha

and 21.3 mtons of total production of wheat grain with average grain yield of 2519 kg ha-

1 (Pakistan statistical year book, 2007). Different conventional approaches related to soil,

crop and fertilizer have been brought under to improve its yield in our country and even

then its per hectare yield is much lower as compared to other agriculturally developed

countries. Under such a situation it becomes more necessary and need of time to use

some non conventional approaches to improve the yield of wheat crop and narrowing

down the gap between potential and farmer’s obtained yields.

Nitrogen (N) is an essential macro nutrient and is mostly deficient in agricultural

lands. To overcome nitrogen deficiency, nitrogenous fertilizers are recommended to use

(Peoples et al., 1995). Most of the fertilizer N applied to soils is in the form of

ammonium or ammonium producing compounds such as urea or ammonium sulfate

(FAO, 2006). These can be lost, depending on the agricultural system and the

environment, by leaching, erosion and runoff, or by gaseous emissions. NH3

volatilization is the major source of N-loss when fertilizers are applied through broadcast

(Freney et al., 1992b) over soil with high pH (Freney et al., 1983). Decreasing NH3 loss

by alternative methods of application to surface broadcasting (eg. incorporation, burying

at depth) is a fact and related to the provision of a physical barrier in the form of a layer

3

of soil to trap the NH3 liberated. However, nitrification and denitrification become the

main loss processes when fertilizer is drilled into depth (Freney et al., 1993).

Nitrification is the biological oxidation of ammonium to nitrate via nitrite affected

by Nitrosomonas and Nitrobacter species of nitrifying bacteria, respectively while

biological denitrification is the dissimilatory reduction of nitrate to nitrite to produce NO,

N2O and N2. The loss of fertilizer N due to these processes is of concern not only because

of economic reasons but also due to the pollution potential of different N forms. Nitrate

formed from nitrification of fertilizer nitrogen applied at depth, having a negative charge

and does not held to exchange sites and either leaches down to the soil bed or enters the

atmosphere via denitrification as gases. A high nitrate contaminated ground water, when

used for drinking, causes methemoglobinemia, a condition which incapacitates blood

haemoglobin to carry oxygen to body cells. Fertilizer nitrogen that enters the atmosphere

in gaseous forms mainly comprises ammonia, nitrous oxide and nitric oxide. Nitrous

oxide (N2O) is a trace gas involved in atmospheric pollution; it contributes to the

greenhouse effect (Smith, 1990), and affects the chemistry of O3 in the upper troposphere

and lower stratosphere (Graedel and Crutzen, 1992). N2O is mainly produced in soils

during biological denitrification and nitrification (Tortoso and Hutchinson, 1990;

Groffman, 1991; Conrad, 1996).

Another aspect of nitrification process is that it affects the choice of crop plants

for N forms to be up taken. Although most plants are able to use both NH4+-N and NO3

--

N, the later is the predominant source of N for plants grown under arable/terrestrial lands.

This is primarily because of compulsion rather than preference, as most of the NH4+-N is

rapidly nitrified under optimum conditions of temperature, moisture and aeration. As a

result, NH4+-N is available to the plants only for a limited time period and for most of the

time, plant roots are confronted with NO3--N as a source of N (Azam and Farooq, 2003).

There may be some exceptional cases but as a general rule, plants produced significantly

higher dry matter yield and greater accumulation of N, with mixed N nutrition than with

NH4+ or NO3

- alone (Cox and Reisenauer, 1973; Heberer and Below, 1989; Chen et al.,

1998; Ali et al., 2001).

Nitrification inhibition of applied fertilizer N is thus desirable as the accumulation

of nitrates in soils in excess of plant needs can adversely affect plant growth and leads to

4

loss by denitrification and leaching (Addiscott et al.,1991). These losses contribute to low

efficiency of fertilizer nitrogen used by crops (van Cleemput et al.,1981; Zhu et al., 1989;

Sisworo et al., 1990), production of the nitrous oxide (Eichner, 1990; Granli and

Bøckman, 1994; Bouwman, 1996), and contamination of groundwater (Johnson et al.,

1987; Ma Li-shan, 1997).

A number of compounds have been tested to inhibit the nitrification process in

soils (Bundy and Bremner, 1973; Hauck, 1983; Slangen and Kerkhoff, 1984) and limited

the emission of nitrous oxide (Aulakh et al., 1984; Magalhaes et al., 1984). Nitrapyrin

(N-serve) and dicyandiamide (DCD) are most widely used and commercially available

nitrification inhibitors. Both of these nitrification inhibitors (NIs) are used in agriculture

with some limitations e.g effectiveness of nitrapyrin is limited due to sorption on soil

colloids, decomposition and volatilization (Keeney 1983; Slangen and Kerkhoff, 1984).

Maftoun et al. (1981) reported nitrapyrin toxicity as leaf chlorosis in cow peas, and

interveinal chlorosis in chick peas. Di and Cameron (2004) reported that at a soil

temperature of 8°C, the half-life of DCD was 111-116 days while at a soil temperature of

20°C the half-life of DCD was 18-25 days. At higher temperature its effectiveness may

further decreased. Secondly DCD is highly soluble in water and thus susceptible to

leaching losses (Mamdouh et al., 1990).

Acetylene is another NI used in agriculture. It has been noted that acetylene, at

partial pressures of 0.1 to 10 Pa, inhibits the ammonia oxidizing enzyme (ammonia

mono-oxygenase), however this inactivation of enzyme is reversible because the

inhibitory effect persists for at least 7 days after acetylene has been removed and the

enzyme is resynthesized by nitrifying bacteria (Berg et al., 1982). Owing to this property

acetylene is currently used to quantify the relative contribution of nitrification and

denitrification to soil emissions of the greenhouse gas, N2O (Klemedtsson et al., 1988).

However, because it is a gas, acetylene as nitrification inhibitor is difficult to

apply and maintain at a required concentration in soils for extended periods. Two

approaches have been tried to overcome these problems. One is to employ non-gaseous

acetylenic compounds in place of acetylene. McCarty and Bremner (1986) compared 21

acetylene releasing compounds in a laboratory study, and reported that 2-ethynylpyridine

and phenylacetylene effectively inhibited nitrification in soil. Freney et al. (1993)

5

confirmed in a field experiment that these two compounds were effective in inhibiting

nitrification of fertilizer N applied in the month before sowing cotton. Unfortunately, 2-

ethynylpyridine is too expensive at present to be used in agricultural production. A

second approach which has been researched is to coat calcium carbide with paraffin wax,

petroleum jelly, clay etc. to slow its reaction with water [CaC2 + H2O → C2H2 + Ca

(OH)2], and produce acetylene in situ in soil.

Patra et al. (2006) suggested that slow release of acetylene (C2H2) from

encapsulated calcium carbide (ECC) has reduced ammonia mono-oxygenase with

reducing population of ammonia oxidizing bacteria and has the potential to retard the

enzyme activities in favour of C and N conservations in a semi-arid agro-ecosystem.

Addition of ECC with the nitrogen fertilizer blocked nitrification in irrigated wheat for

more than 10 weeks, thus preventing denitrification and loss of nitrogen (Freney et al.,

1992a). In addition, loss of applied nitrogen from flooded rice in the Murrumbidgee

Irrigation Area was reduced from 56% to 13% and methane production was also

markedly reduced (Keerthisinghe et al., 1993).

Another aspect of ECC application is that acetylene released from calcium

carbide is reduced to ethylene (C2H4) in the presence of enzyme (nitrogenase) by soil

indigenous microorganisms, which may enter the plant through roots (Muromtsev et al.,

1988; Muromtsev et al., 1993; Bibik et al., 1995). Ethylene is a simple, readily diffusible

gaseous hormone. It is produced in all plant parts including roots, stems, leaves, buds,

flowers and seeds (Chadwick et al., 1986). Microorganisms present in the soil can

produce ethylene from amino acids, carbohydrates, proteins and alcohols (Arshad and

Frankernberger, 1990). Further more its exogenous application provides a new

opportunity for increasing crop production (Arshad and Frankernberger, 1988). Ethylene

regulates multiple developmental processes of plant life including seed germination, fruit

ripening, abscission and senescence (Abeles et al., 1992). It is also a signal mediating

response to a range of both biotic and abiotic stresses (Morgan and Dew, 1997). At the

level of gene expression, ethylene induces transcription of a wide range of genes involved

in wound signaling, defense against pathogens (Ecker and Davis, 1987) and fruit ripening

(Slater et al., 1985). It can also stimulate elongation of certain plant organs (Emery et al.,

1994; Kende et al., 1998) and separation of plant cells as it is involved in the activation

6

of cell wall degrading enzymes (Casadoro et al., 1999). Ethylene inhibits the movement

of auxin in stem tissue, possibly reducing auxin’s ability to promote stem elongation

(Morgan and Gausman, 1966). Seedlings also exhibit a triple response to ethylene

consisting of shortened, thickened hypocotyls and a pronounced apical hook (Abeles et

al., 1992). Several studies indicate that ethylene controls and coordinates a number of

growth and developmental processes, both in vivo and in vitro (Biddington, 1992). In

case of wheat and other cereals, ethylene enhances tillering (Kenneth et al., 1992; Marcia

and Peter, 1982) and prevents lodging (Simmons et al., 1988; Boutaraa, 1991).

In ECC mostly waxes like natural resins were used to encapsulate calcium

carbide. Cost, product variability and difficulty of scale-up might make this system

impractical for large-scale production. In addition, because of the low melting points of

the waxes, problems have occurred with its application by machinery in the field. So a

new and potentially commercial approach to supplying acetylene was sought. Freney et

al. (2000) considered that calcium carbide powder encapsulated in an inert hydrophobic

polymer, like polyethylene, would react more slowly with water and release acetylene

over a longer period than the 10 weeks achieved with ECC. Consequently materials

(called matrices) containing small particles of calcium carbide (1–200 µm dia.),

polyethylene (or polypropylene) and other additives were prepared. The additives were

used to provide microbridging in the matrix and hence controlled water penetration and

acetylene generation and release.

Keeping all these facts in view about calcium carbide as a potent source of

acetylene and ethylene, a series of laboratory, greenhouse and field experiments were

planned to evaluate the effective rate, time and depth f application of calcium carbide for

improving growth, yield and nitrogen use efficiency of wheat crop. Moreover, it was also

tried to find out appropriate coating material to coat calcium carbide grains for slow

release of acetylene and ethylene gases so the effect of these gases can be prolonged for

longer period of time.

7

CHAPTER 2 REVIEW OF LITERATURE

A series of experiments was planned to evaluate the effectiveness of soil applied

calcium carbide on nitrogen (N) use efficiency, growth and yield parameters of wheat.

Literature most pertinent to different aspects of calcium carbide application with respect

to plant growth and development is reviewed under the following headings.

2.1 Nitrogen use efficiency Nitrogen comprises 7 % of total dry matter of plants and is a constituent of many

fundamental cell components such as nucleic acids, amino acids, enzymes, and

photosynthetic pigments (Bungard et al., 1999). High nitrogen supply favors the

conversion of carbohydrates into proteins, which in turn promotes the formation of

protoplasm (Arnon, 1972) and ultimately improves crop plant growth and yield

parameters (Bakhsh et al., 1999; Khan et al., 2000). Due to bulkiness and inadequate

supply of organic sources of N, inorganic fertilizers are now in routine use and N is the

most costly mineral nutrient required for cereal production (Clark, 1990). Adequate

application of nitrogenous fertilizers and new technologies for water management and

other agronomic practices made it possible to introduce high yielding cultivars to increase

yield of crops (Clark, 1990; Bumb,1995). Application of right source, rate, time and

method of application of nitrogen fertilizer is thus considered a key to obtain bumper

crop yield. Recovery of N from nitrogenous fertilizers applied to soil is low due to the

loss of N in the form of leaching, run off and gaseous emissions. Thus, nitrogen fertilizers

are not a straight blessing for agriculture production since crop plants use 50 % or even

less nitrogen of the applied fertilizer and remaining is lost through volatilization, leaching

and denitrification from the soil-plant system (Azam and Farooq, 2003). The relative

contribution of these processes is influenced by fertilizer type, application methodology,

cropping procedures and prevailing soil and atmospheric conditions. Therefore, NH3

volatilization is of supreme importance in sugarcane fields when urea is applied to the

surface of cane residues left over on the soil surface (Freney et al., 1992b). However,

denitrification is the main loss process in irrigated cotton when fertilizer is drilled deep

8

into the soil (Freney et al., 1993), whereas both NH3 volatilization and denitrification are

important when urea is broadcast into flooded rice fields (Freney et al., 1990).

Depending upon the fertilizer technique and environmental conditions, nitrogen

losses through ammonia volatilization varies from negligible to more than 50 % of the

fertilizer N applied (Bacon et al., 1986; Keller and Mengel, 1986; Black et al., 1989;

Freney et al., 1992b). Concentration of ammonium, soil temperature and pH affect the

partial pressure of ammonia in the soil and are important in regulating N losses through

NH3 volatilization. Soil pH particularly affects equilibrium between ammonium and

ammonia so that relative concentration of NH3 increases from 0.1 to 1, 10 and 50 % as

the pH changes from 6 to 7, 8 and 9, respectively (Freney et al., 1983). At a specific pH,

rise in soil and environment temperature increases relative proportion of NH3 to NH4+

and decreases the water solubility of ammonia. This increases the diffusion of ammonia

in the soil and affects microbial transformations of nitrogen. Wind speed is another factor

which affects ammonia volatilization by affecting mixing of ammonia in liquid phase and

its transport from soil-air or water-air interface (Freney et al., 1981; Denmead et al.,

1982; Fillery et al., 1984). Soil texture, moisture content of the soil, pH buffering

capacity, cation exchange capacity, nitrification rate and presence of plant and plant

residues are some of the factors which also affect ammonia volatilization (Freney and

Black, 1988). Thus, in high pH soils of arid and semi arid regions, N is lost mainly due to

NH3 volatilization and can be controlled if N fertilizers are incorporated or deep placed

into the soil. However, nitrogen fertilizers when buried under the soil surface,

nitrification and/or denitrification become the main loss processes of N (Freney et al.,

1993).

Nitrification is the biological oxidation of ammonium to nitrate and is mediated

by Nitrosomonas and Nitrobacter species of bacteria. Ammonium availability and oxygen

supply are important factors which affect nitrification process. Soil moisture content

indirectly controls nitrification by influencing oxygen supply. Upper soil layer and

rhizosphere are zones of active oxygen supply and thus high rates of nitrification. Under

flooded conditions nitrification is mostly occur in water column over the soil surface, at

soil water interface and in rhizosphere. Rice roots also aerate the soil with aeranchymatic

stem. The transport of ammonium by diffusion is influenced by the cation exchange

9

capacity, and organic matter status of the soil, bulk density, rate of nitrification in the

oxidized soil layer, presence of reduced iron and manganese and rice rhizosphere.

Ammonium accumulated during flooding can be nitrified rapidly as the soils dry and

become aerated (Buresh and De Datta, 1991).

The biological reduction of nitrate and nitrite to produce NO, N2O and N2 is

called denitrification. Oxygen, nitrate concentration, pH, organic matter and temperature

of soil are the factors which strongly influence denitrification (Peoples et al., 1995). Soil

water tends to moderate oxygen diffusion in soil and, generally speaking, denitrification

occurs only when the soil water content is >60 % of the air-filled pore space (Linn and

Doran, 1984). Large denitrification events are observed in lowland rice when the soil is

reflooded and then proceed in the reduced soil layer during flooding (Buresh and De

Datta, 1991; Aulakh et al., 1992). Nitrate produces during nitrification process leaches

down to ground water or denitrifies to produce N2O type greenhouse gases. To control

gaseous emissions from fertilizer N, nitrate leaching and to obtain high N use efficiency

by crop plants, nitrification inhibition is thus desirable.

2.2 Type of nitrogen nutrition for crop plants A number of research workers studied plant growth and development under

different ammonium:nitrate nutrition ratios. In an experiment, Lewis and Chadwick

(1983) grew barley plants in pH-controlled, aerated solution culture with 2 mM inorganic 15N supplied as nitrate alone, ammonium alone or 1:1 nitrate:ammonium. It appears that,

for maximum growth and N assimilation of hydroponically-grown barley, a mixed

nitrate-ammonium N source is required. Nitrate is poorly absorbed but appears to be

necessary for the optimum growth of ammonium fed plants by increasing shoot N

assimilation or by providing additional electron accepting potential to the roots. The

situation could be markedly different in soil grown plants where the ammonium ion is not

so readily available. On the other hand under saline conditions both ammonium nutrition

and salinity reduced the uptake of K+ and Ca2+, but increased the uptake of Na+ by two

wheat cultivars and thus led to lower K+/Na+ ratios relative to those in either nitrate-fed,

or non-saline plants. In addition, ammonium nutrition reduced the proportions of plant

K+, Na+ and Ca2+ retained by the root. The toxic effect of ammonium nutrition on wheat

can thus be related to reduced uptake of K+ and Ca2+ and to enhance uptake of Na+. The

10

results suggest that nitrate, rather than ammonium, is favored as a nitrogen source for

both wheat cultivars, particularly under salt stress (Al-mutawa and El-katony, 2001). In

an other study Ali et al. (2001) found that a mixed N supply of NH4+ and NO3

- resulted in

greater accumulation of N in plants than either NH4+ or NO3

- as the sole N source. Plants

produced a significantly higher dry matter yield when grown with mixed N nutrition than

with NH4+ or NO3

- alone. Total dry matter production and root and shoot N contents

decreased with increasing salinity in the root medium. There may be some exceptional

cases but as a general rule, plants produced significantly higher dry matter yield and

greater accumulation of N, with mixed N nutrition than with NH4+ or NO3

- alone (Cox

and Reisenauer, 1973; Heberer and Below, 1989; Chen et al., 1998; Ali et al., 2001). In

arid and semiarid conditions nitrification process is very fast and applied N fertilizer is

immediately nitrified. So in terrestrial environment nitrate becomes the sole source of N

(Azam and Farooq, 2003). Under such circumstances nitrification inhibition may help to

provide mixed nitrogen nutrition to crop plants for longer period of time.

2.3 Nitrification inhibitors Nitrification is the biochemical oxidation of ammonium to nitrate. Nitrosomonas

and Nitrobacter bacterial species are involved in nitrification. Nitrosomonas converts

ammonium to nitrite by the action of ammonia mono-oxigenase enzyme and Nitrobacter

oxidizes nitrite to nitrate. Nitrification inhibition is the inactivation of ammonia mono-

oxigenase enzyme under the chemical action of some nitrification inhibitor. A number of

chemicals have been used to inhibit nitrification in soil. These include 2-chloro-6

(trichloromethyl) pyridine (nitrapyrin), sulfathiazole, dicyandiamide, 2-amino-4-chloro-

6-methyl pyrimidine, 2-mercaptobenzothiazole, thiourea and 5-ethoxy-3-trichloromethyl-

1,2,4-thiadiazole (terrazole). Unfortunately, most of these compounds have limited use

due to one or the other reason (Keeney, 1983). For example, the most commonly used

nitrification inhibitor, nitrapyrin, is seldom effective because of sorption on soil colloids,

hydrolysis to 6-chloropicolinic acid, and loss by volatilization (Hoeft, 1984; Slagen and

Kerkhoff, 1984). Nitrapyrin, dicyandiamide (DCD) and acetylene are most commonly

tested in laboratory and field experiments. Nitrapyrin and DCD are good nitrification

inhibitors but their efficacy is limited, respectively due to volatilization, sorption on soil

colloids and leaching (Keeney, 1983; Slangen and Kerkhoff, 1984; Davies and Williams,

11

1995). It has been established in laboratory studies that acetylene is a potent inhibitor of

nitrification (Walter et al., 1979; Hynes and Knowles, 1982). Encapsulated Calcium

Carbide (ECC) or Coated Calcium Carbide (CCC) is an acetylene releasing compound

and is being successfully used in agriculture to inhibit nitrification (Aulakh et al., 2001;

Randall et al., 2001; Yaseen et al., 2006)

2.4 Calcium carbide as a nitrification inhibitor Calcium carbide releases acetylene gas when comes in contact with moisture.

Acetylene is recognized as potent nitrification inhibitor and at partial pressures of 0.1 to

10 Pa, inhibited the ammonia oxidizing enzyme, ammonia mono-oxygenase. The

inactivation of enzyme was reversible and inhibitory effect persists for at least 7 days

after acetylene had been removed and the enzyme was resynthesized by nitrifying

bacteria (Berg et al., 1982). However, Walter et al. (1979) reported that acetylene

concentration required to inhibit nitrification was 0.1 % (vol/vol). The ability of

acetylene to inhibit nitrification varies with soil type. It was noted that low acetylene

partial prepessures were insuffcient to totally inhibit nitrification in a hypercalcareous

Rendosol at water potentials higher than -3.5 MPa while they were always sufficient in a

redoxic Luvisol (Garrido et al., 2000).

Calcium carbide is a common ripening material (Vrebalov et al., 2002;

Barry et al., 2005). Banerjee and Mosier (US Pat. Appl.07/229,386, 8 Aug. 1988)

encapsulated calcium carbide (CaC2) with waxes and checked for nitrification

inhibition. They conducted a series of laboratory and green house experiments in

unplanted soils. Their studies indicated that coated CaC2 (ECC) could effectively inhibit

NH4+ oxidation under both flooded and unflooded soil conditions. They also claimed that

oxidation is only delayed not stopped (Banerjee and Moiser, 1989; Patra et al., 2006). In

planted soil (wheat-rice cropping system), ECC when applied in combination with

Sesbania sesban, soil NH4+ and total mineral-N (NH4

+ + NO3–) contents were enhanced.

Dehydrogenase and nitrate reductase activities and population of ammonia oxidizing

bacteria revealed a significant reduction in soils, whereas nitrite oxidizing bacteria

remained almost unaffected (P > 0.05) in response to application of ECC with Sesbania

sesban and urea. Results suggested that ECC has the potential to retard the enzyme

activities in favor of carbon (C) and N conservations in a semi-arid agro-ecosystem (Patra

12

et al., 2006). In another wheat field, wax coated calcium carbide limited ammonium

oxidation, prevented nitrogen loss by denitrification for 75 days and resultantly increased

N accumulation by wheat plants. Thus a 46 % greater recovery of applied nitrogen was

observed in the plant-soil system at harvest. However, the inhibitor treatment did not

increase grain yield because of waterlogging at the end of tillering and during stem

elongation (Freney et al., 1992a). Increase in nitrogen accumulation in wheat tops, owing

to nitrogen transformations with calcium carbide application is also reported by Smith et

al. (1993).

Soil application of calcium carbide also affected gaseous emissions from soil

surface. It was noted that ECC strongly mitigated the emissions of N2, N2O and CH4.

Emission of CO2 was also comparatively decreased when encapsulated calcium carbide

was applied to flooded pots placed in green house (Bronson and Mosier, 1991). Under

field conditions with corn as a test crop, Bronson et al. (1992) banded ECC (0, 20, or

40 kg ha-1) with urea (218 kg N ha-1) 7 weeks after planting corn. Between 1 and

14 weeks after fertilization, N2O losses of 3226, 1017, and 1005 g N2O-N ha-1

from urea alone, urea plus 20 kg ECC ha-1, 40 kg ECC ha-1, respectively, were

measured from vented chambers. Nitrous oxide was positively correlated with

soil NO3 levels, indicating that nitrification inhibitor indirectly controlled N2O

emissions by preventing NO3 from accumulating in the soil. Carbon dioxide

emissions from root zone were not affected by ECC. In flooded water, 50 % of the

applied N was lost when urea was broadcasted into the floodwater. Total N loss from the

applied nitrogen was significantly reduced when urea was either incorporated or deep

placed in the presence of encapsulated calcium carbide. The losses were reduced further

and the lowest loss was noted when urea was deep placed with encapsulated calcium

carbide (Keerthisinghe et al., 1996).

2.5 Comparison of encapsulated calcium carbide with other nitrification inhibitors Under aerobic soil conditions with cotton as a test crop, nitrification inhibitors

(NI,s) significantly affected N transformation and de-nitrification. Addition of acetylene,

phenylacetylene and nitrapyrin reduced nitrogen losses over 24 weeks of sowing as 57,

52 and 48 %, respectively (Chen et al., 1994). In flooded rice micro plots, Keerthisinghe

13

et al. (1993) compared wax coated calcium carbide and nitrapyrin for nitrification

inhibition. They found that nitrapyrin and acetylene from calcium carbide significantly

reduced methane emission and lowest emission rate was observed in the wax coated

calcium carbide treatment. In an other experiment conducted under upland flooded

conditions, nitrification of the applied 100 mg NH4-N kg–1 soil was retarded most

effectively (93 %) by ECC for up to 10 days of incubation, whereas for longer periods, 4-

amino- 1,2,4-triazole (ATC) was more effective. After 20 days, only 16 % of applied

NH4-N was nitrified with ATC as compared to 37 % with dicyandiamide (DCD) and 98

% with ECC. Under flooded soil conditions, nitrates resulting from nitrification quickly

disappeared due to denitrification, resulting in a tremendous loss of fertilizer N (up to 70

% of N applied without NI). Based on four indicators of inhibitor effectiveness, namely,

concentration of NH4-N and NO3-N, percent nitrification inhibition, ratio of NH4-N:NO3

-N, and total mineral N, ECC showed the highest relative efficiency throughout the 20-

day incubation under flooded soil conditions. At the end of the 20-day incubation, 96 %,

58 % and 38 % of applied NH4-N was still present in the soil where ECC, ATC and DCD

were used, respectively. Consequently, nitrification inhibition of applied fertilizer N in

both arable crops and flooded rice systems could tremendously minimize N losses and

help to enhance fertilizer N-use efficiency. These results suggest that for reducing the

nitrification rate and resultant N losses in flooded soil systems (e.g. rice lowlands), ECC

is more effective than costly commercial NI,s (Aulakh et al., 2001).

2.6 Role of ethylene in crop production Acetylene released from calcium carbide is reduced to ethylene (C2H4) by soil

microorganisms (Muromtsev et al., 1988). Ethylene as a gaseous phytohormone

(Mattoo and Suttle, 1991) whether endogenously synthesized in the plant body,

evolve in plant in response to environmental stress (Lurssen, 1991) or supplied

exogenously has a marked effect on plant growth and development (Arshad and

Frankenberger, 2002; Grodzinski and Woodrow, 1989). It is reported that

ethylene binding is required for dormancy release of seeds of many plant species. In most

of the cases ethylene can stimulate the germination of seeds which may be inhibited due

to embryo or coat dormancy, adverse environmental conditions or due to inhibitors

(Abeles and Lunski, 1969; Stewart and Freebairn, 1969; Ketring and Morgan, 1970;

14

Burdett and Vidaver, 1971; Burdett, 1972a; Negm et al., 1972; Keys et al., 1975; Rao et

al., 1975; Dunlap and Morgan, 1977; ketring, 1977; Esashi, 1978; Egley, 1980; Abeles,

1986; Gallardo, 1991; Huang and Khan, 1992; Dutta and Bradford, 1994; Kepczynski

and kepczynska, 1997; Nascimento, 1998; Nascimento et al., 1999a, 1999b; Pech et al.,

1999; Beaudoin et al., 2002; Ghassemian et al., 2002), however sometimes it delays or

does not affect seed germination (Esashi et al., 1991). In case of salinity induced seed

dormancy ethephon (an ethylene releasing liquid compound) is reported to promote

germination of all salinities. Seed germination of Allenrofea occidentalis

(Chenopodiaceae) seeds was zero at salinity level of 800 mM NaCl. Fusicoccin (5µ M),

Ethephon ( 10µ M ) and nitrogenous compounds (20 µ M nitrate and 10 µ M thiourea)

were able to counteract the inhibition produced by salinity (Gull and Darrell, 1998).

Dormant seeds or non-dormant inhibited seeds have low ethylene production ability and

1-aminocyclopropane-1-carboxylic acid (ACC) and ACC oxidase activity than non-

dormant uninhibited seeds (Kepczynski and kepczynska, 1997). In an other experiment

during the formation of somatic embryos from leaf discs of Coffea canephora, explants

always produced a small amount of ethylene. Removal of this ethylene by an absorbent

reduced the number of somatic embryos induced by the cytokinins. Application of

inhibitors of production of ethylene (Co2+ ions) and of the action of ethylene (Ag+ ions)

inhibited the formation of embryos. Exogenous ethylene (12 µL L-1 ) partially overcome

the effect of Co2+ ions. These results indicated that ethylene plays an important role in

regulating somatic embryogenesis in leaf cultures of Coffea canephora (Tomoko et al.,

1995).

Ethephon (ethylene releasing compound) application significantly affected

vegetative growth of “Tifton 85” burmudagrass (Cynodon dactylon L.) plants and a 22 %

reduction in plant height, node swelling, bud swelling at the crown, terminal leaf

necrosis, chlorotic stripping of young developing leaves and 118 % and 101 % increase

in leaf/stem fresh and dry weight ratios, respectively were noted. In glass house

experiments, vegetative cuttings taken from ethephon treated plants produced 112 %

more roots under a range of water stress conditions 8 days after removal of cutting and

produced 10 fold higher number of tillers at 6 days after planting in soil (Robert et al.,

1998). In some other cases response of plant root growth to exogenously applied

15

ethylene varies with gas concentration as well as plant species. Smith and

Robertson (1971) noted that ethylene at concentration of <1ppm inhibited

extension of roots in barley whereas increased root extension in rice and rye. But

concentration of 10 ppm reduced root extension in both rice and rye, the

reduction was up to 25 % in rice and up to 40 % in rye. In an other experiment

application of ethephon alone and in a mixture with mepiquat chloride, either as

a seed treatment or foliar application, inhibited root growth in barley when

measured 2 to 3 weeks after application (Woodward and Marshall, 1987, 1988).

A positive response of root growth and development to ethylene is also reported by

Cooke et al. (1983). Ethylene also affected the water transport ability of roots of Aspen

(Populus tremuloides) seedlings grown in solution culture. Short term exposure of roots

to exogenous ethylene significantly increased, root hydraulic conductivity (Lp), root

oxygen uptake and stomatal conductance in hypoxic seedling. Aerated roots that were

exposed to ethylene also showed enhanced hydraulic conductivity (Lp). An ethylene

inhibitor, silver thiosulfate, significantly reversed the enhancement of Lp by ethylene

(Kamaluddin and Zwiazek, 2002).

Ethrel (an ethylene producer) application @ 2.24 kg ha-1 effectively

reduced lodging in wheat and oats crops. While application @ 0.56 kg ha-1

increased yield significantly. The increase was 15.8 % in wheat and 7.8 % in oats

(Brown and Early, 1973). Ethephon reduced lodging and plant height, and

increased grain yield of wheat on an average by 6.4 % (Wiersma et al., 1986).

The reduction in elongation of tall cereals and increase in the harvestable yield

by reducing lodging with ethephon application is also reported by Dahnous et al.

(1982). The reduction in plant height of cereals was due to ethylene, produced upon

ethephon application and changes the orientation of new cell wall deposition by changing

the orientation of the cortical microtubule array of the cell and then the cells expand only

laterally, producing thick shoots which are lodging resistant in both arid and semiarid

regions (Alberts et al., 1989; Bleecker et al., 1988; Harms, 1986;). Reduction in plant

height due to ethylene is also reported by Rajala and Peltonen-Saino (2001) and Rajala et

al. (2002). Ethephon and mepiquat chloride, alone and in mixtures, stimulated

tillering and occasionally increased the number of spike-bearing tillers

16

(Cartwright and waddington, 1982; Klassen and Bugbee, 2002). In another

experiment ethephon typically increases barley (Hordeum vulgare L.) spikes per square

meter by increasing the frequency of late emerging green tillers, resulting in uneven crop

maturity. Ethephon did not affect grain yield or protein content, but it often reduced

volume mass and kernel plumpness compared to the untreated control. Regardless of

ethephon treatment, kernels on late emerging tillers were of lower mass, volume mass,

and plumpness than kernels on early emerging tillers. These late emerging green tillers

contributed 8 % to the total grain yield but produced grain of substandard malting quality

(Lauer, 1991). In the above situations increase in tiller formation may be due to

changes in responsiveness to day length (Hutley-Bull and Schwabe,1982). When

applied to corn, ethephon @ 0.14 - 0.84 kg ha-1 significantly affected grain yield, plant

height, ear height and brace root development. The yield of one hybrid variety generally

decreased with increasing ethephon rates whereas the lowest rates (0.14 kg ha-1)

increased the yield of another hybrid variety up to 700 kg ha-1 (Langan and Oplonger,

1987). In another experiment on corn crop, application of high rates of ethephon reduced

lodging by 87 % and increased brace root development by 50 %. However, increasing

application rates generally decreased yields (Gaska and Oplinger, 1988). In case of rice,

foliar application of ethephon increased grain yield by 10 - 45 % (Rao and Fritz, 1987).

Time of application of ethylene is also important for yield and yield components of

cereals. Ethephon decreased the grain yield of barley when sprayed at tillering and stem

elongation compared with the later flowering stage for both arid and semiarid regions.

However when ethephon was used with supplementary irrigation, it was found to

increase grain yield, spike m-2 and earliness (Al-Jamali et al., 2002). According to Hill et

al. (1982), Bahry (1988) and Ramos et al. (1989) cereals grain yield increase with

exogenous application of ethylene in the absence of lodging might be attributed to

increase in number of spike bearing tillers per unit area.

Exogenous 1-aminocyclopropane-1-carboxylic acid (ACC) at 100 µM enhanced

ethylene production by barley seedlings and stimulated shoot growth, whereas both

germination and seedling growth were inhibited by antagonists of ethylene perception i.e.

75 µM silver ions, 100 µM 2,5-norbornadiene (Jacquiline et al., 2000). Shoot growth

responses to applied ethylene were also studied by Fiorani et al. (2002) in four Poa

17

(meadow-grass) species that differ inherently in leaf elongation rate and whole plant

relative growth rate. Compared with the fast-growing Poa annua and Poa trivialis, the

shoots of the slow growing species Poa alpine and Poa compressa emitted daily 30 to 50

% less ethylene and their leaf elongation rate was more strongly inhibited when ethylene

concentration was increased upto 1µL L-1. However, low ethylene concentrations (0.02 –

0.03 µL L-1) promoted leaf growth in the two slow growing species; at the same

concentrations, leaf elongation rate of the two fast growing species was only slightly

inhibited. All responses were observed within 20 minutes after ethylene application.

Although ethylene generally inhibits growth. Results showed that in some species, it may

actually stimulate growth. In case of rice total above ground biomass, number of tillers,

grain yield and number of panicles were significantly increased with elevated level of

CO2. Seneweera et al. (2003) concluded that elevated CO2 stimulated 2-3 fold increases

in endogenous ethylene release, which may be central in promoting accelerated

development. Increase in coleoptiles length, leaf length and mesocotile length of etiolated

rice seedlings was also noted when these seedlings were exposed to ethylene (Raskin and

Kende, 1983). In another experiment ethephon, chlormequat chloride (CCC), and

trinexapac–ethyl (TE) were applied during early growth stages to barley (Hordeum

vulgare L.), oat (Avena sativa L.), and wheat (Triticum aestivum L.) cultivars grown

either in sand mixture or in clay illitic topsoil. The application of these plant growth

regulators reduced main shoot growth in barley and wheat up to 20 %. Tiller production

was enhanced by ethephon and TE treatment in all species, but not adequately to

compensate for PGR-induced reduction in main shoot growth. Carbon dioxide exchange

rate was reduced temporarily by ethephon and TE treatments in Mahti wheat. Plant

growth regulator applications have modest potential for modifying traits of spring cereal

plant stand structure other than straw length (Rajala and Peltonen-Saino, 2001).

Yang et al. (2004) conducted an experiment to test the hypothesis that the

interaction between abscisic acid (ABA) and ethylene may be involved in mediating the

effect of water stress on grain filling. Grain filling rate and grain weight were

significantly increased under mild water stress but decreased under severe water stress.

ABA concentration in the grain was very low during the grain filling stage, reaching a

maximum when the grain filling was highest. In contrast to ABA, concentration of

18

ethylene and 1-aminocyclopropane-1-carboxylic acid (ACC) in the grains were very high

at early grain filling stage and sharply decreased during the linear period of grain growth.

These results indicated antagonistic interactions between ABA and ethylene that mediate

the grain filling, and a high ratio of ABA to ethylene enhances grain filling rate. In

another experiment Beltrano et al. (1997) found that ethylene production increased

only slightly under conditions of a moderate or severe water stress. However, the

rehydration of the plants at full turgor after desiccation caused a high emission

of ethylene. 2.7 Effect of calcium carbide on growth and yield of crops

Soil applied encapsulated calcium carbide slowly react with water to produce

acetylene which is reduced to ethylene by soil indigenous microbes (Yaseen et al., 2006

and Kashif et al., 2007). Acetylene being a nitrification inhibitor gas and ethylene as a

plant growth regulator are important in affecting soil nitrogen economy and crop plant

growth and yield parameters (Mahmood et al., 2002). In a field experiment Hazzrika and

Sarkar (1996) coated urea with calcium carbide and applied to rice. They found that

coating of urea with calcium carbide reduced the N losses and increased the fertilizer N

recovery by rice and hence increased grain yield of rice. In a rice-wheat cropping system,

effect of phosphatic fertilizer, calcium carbide and calcium monohydroxymonohydride

(CMMH) on nitrogen utilization efficiency was studied. Results showed that growth and

yield of both the crops were enhanced by the application of these fertilizers and

chemicals; 60 ppm of N with 80 ppm of calcium carbide or CMMH gave wheat yields

comparable and equal to that with 120 ppm of N through urea (Sharma and Yadav,

1996). In another case where soil nitrogen losses via leaching and denitrification were not

significant, application of calcium carbide matrix delayed the disappearance of ammonia

derived from urea but gave no benefits for maize crop yield (Randall et al., 2001).

Saleem et al. (2002) conducted a field experiment to evaluate the influence of

encapsulated calcium carbide on growth, yield and chemical composition of okra. They

found that CaC2 application @ 90 kg ha-1 was most effective in increasing horizontal

expansion of plant, yield of green pods, number of green pods per plant, fresh and dry

weights of shoot and root and internodes length, while plant height decreased with

increase in CaC2 application rate. The chemical analysis of plant material revealed that P

19

and K in green pods and roots were increased with increase in CaC2 application rate. P

contents in shoots were decreased while that of K increased with increase in CaC2

application from 0-90 kg ha-1. Positive response of okra to calcium carbide application is

also reported by Kashif et al. (2008). They applied calcium carbide @ 0, 30 and 60 kg

ha-1 placed 6 cm deep in soil between the plants 2 weeks after germination. Based upon

the results obtained from the laboratory and field trials, it was concluded that calcium

carbide can effectively be used as a nitrification inhibitor (acetylene) as well as plant

growth regulator (ethylene). Okra showed an increase in green pod yield up to 37 % with

the application of calcium carbide @ 60 kg ha-1of soil along with half of the

recommended N fertilizer (60 kg N ha-1) as compared to control while this increase was

about 19 % compared to fertilizer alone. Effect of calcium carbide with and without

fertilizer on growth and yield of rice (Oryza sativa L.) was studied by Rahim et al.

(2004). Results of the study indicated that calcium carbide plus recommended NPK

fertilizers application increased the paddy yield by 19 % over recommended NPK

fertilizers alone. Further it was noted that calcium carbide was effective in improving the

crop yield and N-recovery. Beneficial effects of ECC application on rice growth and

yield were also reported by Yaseen et al. (2005). They noted that ECC applied alone or

along with chemical fertilizer to flooded rice, significantly increased early emergence of

panicles, number of tillers and paddy yield. Soil amended with encapsulated CaC2

resulted in 20 % increase in paddy yield over NPK fertilizer alone. Plant analysis also

indicated that encapsulated CaC2 promoted N concentration and uptake by plant which is

supported by the reduced oxidation of applied fertilizer NH4+ to NO3

- in the presence of

encapsulated CaC2. Taking wheat as a test crop Mahmood et al. (2005) conducted a pot

experiment in the wire-house. Powdered CaC2 was filled in medical capsules and applied

@ 30, 60, 90 and 120 kg ha-1 with and without NPK fertilizers at three times i.e. at

sowing, 2 and 4 weeks after sowing. Number of tillers, root dry weight, 1000-grain

weight, grain yield, straw yield and N uptake were significantly increased by the

application of CaC2 plus NPK compared to NPK fertilizer alone and control. Results

indicated that application of CaC2 @ 60 kg ha-1 applied two weeks after sowing seemed

appropriate rate as maximum number of tillers, root weight, grain yield and N uptake

were obtained by this treatment. Results also indicated that CaC2 increased the grain yield

20

by influencing the yield contributing parameters through changing the growth pattern and

better acquisition of nutrients, which is a typical characteristic of acetylene/ ethylene

released from CaC2. Increase in economical yield of wheat owing to the better root

growth due to CaC2 application is also reported by Ahmad et al. (2004) and Yaseen et al.

(2004).

In short, nitrogen use efficiency is low in arid and semiarid regions due to loss of

fertilizer N by ammonia volatilization, nitrate leaching, run off and gaseous emission via

denitrification. Due to rapid nitrification process N is available in soil as nitrate for most

of the time. Whereas mixed nitrogen nutrition is considered better for plant growth and

development than either nitrate-N or ammonium-N alone. To reduce N loss via leaching

and/or denitrification and to provide mixed nitrogen nutrition to crop plants nitrification

inhibition is thus desirable. A number of chemicals have been identified as successful

nitrification inhibitors but most of them are not suitable for agriculture use. Acetylene is a

good nitrification inhibition gas and calcium carbide is considered a slow releasing

acetylene source. When tested in a number of laboratory and field experiments, CaC2

application inhibited nitrification more effectively than other NI’s. Acetylene released

from CaC2 reduces to ethylene by soil microbes. Ethylene is a plant growth regulator and

is reported to enhance root growth, tillering, grain yield by reducing plant height and

lodging in cereals. As a source of acetylene and ethylene, encapsulated calcium carbide

improved growth and yield parameters of different crop plants and enhanced economical

crop yield upto 30 % or more.

21

CHAPTER 3 MATERIALS AND METHODS

The basic approach of encapsulating calcium carbide to provide a slow release

source of acetylene was proposed by Banerjee and Mosier (1989) (US Pat.

Appl.07/229,386, 8 Aug. 1988). These workers pointed out that encapsulating substance

must not be reactive with calcium carbide and must not be toxic to soil and aquatic fauna

and flora. They favored the use of natural resins as encapsulates and calcium carbide

particles of 2 mm in diameter. Freney et al. (2000) considered that calcium carbide

powder encapsulated in an inert hydrophobic polymer, like polyethylene, would react

more slowly with water and releases acetylene over a longer period than 10 weeks

achieved with wax coated calcium carbide. The research work described in this

manuscript was comprised of preparation, selection and evaluation of different calcium

carbide based slow release sources of acetylene with respect to wheat growth and yield

parameters. The detailed methodology used in different experiments is given in following

pages.

3.1 Experiment 1 Effect of Rate of Encapsulated Calcium Carbide on Growth, Yield and Nitrogen Uptake of Wheat (Pot Trial)

3.1.1 Site of experiment Pot trial was conducted at wire house of Institute of Soil and Environmental

Sciences, University of Agriculture Faisalabad, Pakistan, under natural environmental

conditions, to evaluate the effect of rate of calcium carbide on wheat growth and yield

parameters and nitrogen uptake by plant.

3.1.2 Soil preparation The surface soil from 0-30 cm depth was collected from the research area of

Institute of Soil and Environmental Sciences, University of Agriculture, Faisalabad,

22

Pakistan. The soil was air-dried, ground and passed through 2 mm sieve and analyzed for

physical and chemical properties as described in section 3.1.3.

3.1.3 Soil analysis Soil was analyzed for physical and chemical properties (Table 3.1) by using

methods described by US Salinity Lab. Staff (1954) unless otherwise mentioned.

3.1.3.1 Mechanical analysis

Fifty grams of air dried soil was taken in 500 ml beaker; 40 ml of 1 % solution of

sodium hexametaphosphate and 150 ml of distilled water were added to the beaker and

kept for over night soaking. Soil suspension was stirred with a mechanical stirrer for ten

minutes and transferred to 1000 ml cylinder. The suspension was shaken vigorously with

metal plunger. Initial reading was recorded after 40 seconds of the shaking and final

reading was noted after 2 hours on Bouyoucos Hydrometer (Moodie et al., 1959). Soil

texture class was established by Textural Classification System developed by United

States Department of Agriculture.

3.1.3.2 Saturation percentage

Weighed amount of saturated soil paste was transferred to a tarred china dish and

placed in an oven at 105˚C to achieve the constant weight. Saturation percentage was

calculated by using the formula.

(Mass of wet soil – Mass of oven dry soil)

Saturation percentage = × 100 Mass of oven dry soil

3.1.3.3 pH of saturated soil paste (pHs)

Saturated soil paste was prepared and allowed to stand for one hour and pH was

recorded by using Kent EIL 7015 pH meter after standardization with buffers of pH 4.0

and 9.0 (Method 21a)

3.1.3.4 Electrical conductivity of saturated soil extract (ECe)

Extract of saturated soil paste was taken by using vacuum pump (Method 3a) and

digital Conductivity Meter Model 4070 was used to measure electrical conductivity of

extract (Method 4b).

23

3.1.3.5 Carbonates and bicarbonates

Carbonates and bicarbonates in the saturation extract obtained in section 3.1.3.4

were determined by titration against 0.1 N H2SO4 (Method 12).

3.1.3.6 Chlorides

Chloride in the saturation extract obtained in section 3.1.3.4 was determined by

titration against 0.05 N silver nitrate solution. Potassium chromate was used as an

indicator to note the end point (Method 13).

3.1.3.7. Sulphate

Sulphate was determined by difference as is given below

Sulphate (meq L-1) = TSS – (CO32¯ + HCO3¯ + Cl¯)

3.1.3.8 Sodium and potassium

Soluble sodium and potassium in the saturated soil extract obtained in section

3.1.3.4 were determined by using Jenway PFP Flam Photometer. Salts of NaCl and KCl

were used to prepare standard solutions of sodium and potassium, respectively.

3.1.3.9 Calcium and magnesium

Soluble calcium plus magnesium in the saturated soil extract obtained in section

3.1.3.4 were determined by titration of saturated soil extract against 0.01 N EDTA

(ethylene diamine tetraacetic acid) solution using eriochrome black-T as an indicator

(Method 7)

3.1.3.10 Cation exchange capacity (CEC)

Five gram soil was taken in centrifuge tube and washed three times successively

with 1.0 N sodium acetate, ethanol and 1.0 N ammonium acetate solution, respectively.

Supernatant liquid of ammonium acetate washings was stored in 100 ml volumetric flask

and volume was made up to the mark. Sodium concentration of this liquid was

determined by using Jenway PFP Flame Photometer and cation exchange capacity was

calculated (Method 19).

3.1.3.11 Organic matter

Ten ml of 1.0 N potassium dichromate solution, 20 ml of concentrated sulphuric

acid, 150 ml of distilled water and 25 ml of 0.5 N ferrous sulphate were added to 1 g soil

sample. Excess of FeSO4 was titrated against 0.1 N solution of potassium permanganate

to pink end point (Moodie et al., 1959).

24

3.1.3.12 Total nitrogen

Ten grams soil, 30 ml concentrated H2SO4 and 10 grams of digestion

mixture (K2SO4 : FeSO4 : CuSO4 = 10 : 1 : 0.5) were taken in Kjeldahl’s

digestion tubes and digested till transparent. Then cooled and made the volume

upto 250 ml. Twenty ml of aliquot was taken from this for distillation of

ammonia into a receiver containing 4 % boric acid solution and mixed indicator

(boromocresol green and methyl red). Sodium hydroxide (40 %) was added to the

distillation flask to make the contents alkaline. After distillation, the material in

the receiver was titrated against 0.1 N H2SO4 by Gunning and Hibbard’s method

of H2SO4 digestion and distillation with micro Kjeldahl apparatus (Jackson,

1962).

3.1.3.13 Available phosphorus

Five gram soil was extracted with 0.5 M sodium bicarbonate solution having pH

8.5. A 5 ml aliquot from clear filtrate was taken in 25 ml volumetric flask and 5 ml of

color developing reagent (ascorbic acid, ammonium molybdate, antimony potassium

tartarate and sulphuric acid) was added. Volume was made up to the mark with distilled

water and reading was recorded by T80 UV/VIS Spectrophotometer (Watanabe and

Olsen, 1965).

3.1.3.14 Available potassium

Soil was saturated and then extract was taken with 1.0 M ammonium acetate

solution (pH 7.0). Available potassium was determined by Jenway PFP-7 Flam

Photometer (Method 8).

3.1.4 Pot filling Earthen pots (25 cm long and 15 cm diameter) were lined with polyethylene sheet

and filled with soil @ 12.5 kg pot-1 with gentle packing.

3.1.5 Layout of experiment Ten seeds of wheat cv. Inqulab-91 per pot were sown at 1 cm depth and only five

seedlings were maintained after germination at two-leaf stage. Uprooted plants were

incorporated in the same pot. Nitrogen (N), phosphorus (P) and potassium (K) were

applied at recommended rate of 60-45-30 mg kg-1 soil in the form of fertilizer urea,

diammonium phosphate (DAP) and sulphate of potash (SOP), respectively. All P and K

25

were added to the soil at sowing time. Nitrogen was applied in two splits i.e. half at

sowing time and remaining half dose after two weeks of germination. Pots were irrigated

with canal water to keep the moisture level of soil approximately near to field capacity.

Weeds were uprooted manually, chopped and mixed within the same pot soil. Necessary

plant protection measures were adopted for all the pots during the crop growth period.

3.1.6 Encapsulation of calcium carbide

Required amount of powdered calcium carbide (27 % a.i. CaC2, Ningxia National

Chemical Group Co. Ltd., China) was weighed and filled in medical grade gelatin, empty

capsules (BD-Medical Supplies, Lahore, Pakistan) as shown in Figure 3.1.

Fig. 3.1 Encapsulation of calcium carbide

3.1.7 Treatment plan Encapsulated calcium carbide (ECC) was applied at sowing time of wheat seed in

the centre of pot 4 cm deep according to the following treatment plan.

T1 = nitrogen @ 0 mg kg-1 soil and ECC @ 0 mg kg-1 soil (0-0)*

T2 = nitrogen @ 60 mg kg-1 soil and ECC @ 0 mg kg-1 soil (60-0)

T3 = nitrogen @ 60 mg kg-1 soil and ECC @ 7.5 mg kg-1 soil (60-7.5)

T4 = nitrogen @ 60 mg kg-1 soil and ECC @ 15 mg kg-1 soil (60-15)

T5 = nitrogen @ 60 mg kg-1 soil and ECC @ 22.5 mg kg-1 soil (60-22.5)

T6 = nitrogen @ 60 mg kg-1 soil and ECC @ 30 mg kg-1 soil (60-30)

T7 = nitrogen @ 60 mg kg-1 soil and ECC @ 37.5 mg kg-1 soil (60-37.5) * Values in parenthesis show N-CaC2 amount in mg kg-1 soil

Nitrogen @ 60 mg kg-1 soil (120 kg ha-1) is the recommended rate of N fertilizer

for cv. Inqulab-91 and different ECC rates are chosen on the bases of preliminary trial

results. Calcium sulfate was added to adjust the amount of calcium added from CaC2 in

all treatments where CaC2 was not applied.

26

3.1.8 Parameters studied Following parameters were studied during growth period or at final

harvest.

3.1.8.1 Plant height

Heights of all plants from each pot were measured in cm with meter rod and

means were taken.

3.1.8.2. Number of total and fertile tillers pot-1

Total and fertile tillers were counted from each pot at the completion of tillering

and booting stage, respectively.

3.1.8.3 Root weight

Root bolls from each pot were taken out and washed under tape water to separate

the soil from the roots. Air dry weight of roots was recorded with the help of electrical

balance.

3.1.8.4 Biological yield

Each pot was harvested and tied into bundle. Biological yield was recorded by

weighing the bundle of each pot with digital electrical balance.

3.1.8.5 Grain yield

The bundles were first sun-dried and then threshed manually. The grain weight

was recorded in grams with the help of digital electrical balance.

3.1.8.6 Straw yield

Straw yield was calculated by the difference of biological yield and grain yield.

3.1.8.7 Nitrogen concentration in different plant parts

Dried and powdered straw, grain and root material (1.0 g) was digested

using 20 ml of H2SO4 (conc.) and 8 g of digestion mixture (K2SO4 : FeSO4 :

CuSO4 = 10 : 1 : 0.5 ) for each sample. When the solution became transparent

and yellowish green, it was allowed to cool and transferred to 100 ml volumetric

flask and made up to the mark. The solution was filtered and stored in plastic

bottles for further analysis. 10 ml of aliquot was taken from the above-prepared

solution for distillation. Nitrogen evolved as ammonia was collected in receiver

containing boric acid (4 %) solution and mixed indicator (Bromocresol green and

27

methyl red) and titrated against 0.1N H2SO4 and distillation with micro

Kjeldahl’s apparatus (Jackson, 1962).

3.1.8.8 Nitrogen uptake by straw or grain

Nitrogen uptake by straw or grain was calculated by multiplying straw or grain

yield with nitrogen concentration (%) in straw or grain, respectively.

3.2 Experiment 2 Effect of Time of Application of Encapsulated Calcium Carbide on Growth, Yield and Nitrogen Uptake of Wheat (Pot Trial) 3.2.1 Site of experiment

Site and conditions of experiment are the same as described in section 3.1.1.

3.2.2 Soil preparation Soil was collected from the same field as in case of experiment 1 and prepared as

described in section 3.1.2.

3.2.3 Soil analysis Same procedures were adopted to analyze soil as described in section 3.1.3.

3.2.4 Pot filling Pots were filled as described in section 3.1.4.

3.2.5 Layout of experiment Layout of the experiment and agronomic practices were same as described in

section 3.1.5 except treatments as described in section 3.2.7.

3.2.6. Encapsulation of calcium carbide Encapsulation of calcium carbide was done in similar manner as described in

section 3.1.6.

3.2.7. Treatment plan Encapsulated calcium carbide (ECC) was applied in the centre of pot, 4 cm deep

and @ 22.5 mg kg-1 soil which was found appropriate rate in experiment 1. The

experiment was conducted according to the following treatment plan.

28

T1 = Nitrogen @ 0 mg kg-1 soil and ECC @ 0 mg kg-1 soil

T2 = Nitrogen @ 60 mg kg-1 soil and ECC @ 0 mg kg-1 soil

T3 = Nitrogen @ 60 mg kg-1 soil and ECC @ 22.5 mg kg-1 soil applied at sowing time of

wheat

T4 = Nitrogen @ 60 mg kg-1 soil and ECC @ 22.5 mg kg-1 soil applied 2 weeks after

sowing

T5 = Nitrogen @ 60 mg kg-1 soil and ECC @ 22.5 mg kg-1 soil applied 4 weeks after

sowing

Calcium sulfate was added to adjust the amount of calcium added from CaC2 in all

treatments where CaC2 was not applied.

3.2.8. Parameters studied Different growth, yield and analytical parameters were studied in the same

manner as described in section 3.1.8.

3.3 Experiment 3 Evaluation of Different Type of Calcium Carbide Based Formulations for the Release of Acetylene and Ethylene Gases and Their Effect on Nitrification Inhibition under Laboratory Conditions

3.3.1 Preparation of calcium carbide formulations The step wise procedure adopted for the preparation of different calcium carbide

formulations is described as under.

3.3.1.1 Grinding and sieving of calcium carbide

Bigger calcium carbide stones (27% a.i. CaC2, Ningxia National Chemical Group

Co. Ltd., China) were broken to smaller ones with a mechanical hammer (Fig.3.2a)

especially designed for this purpose. Then particles of about 3-4 cm diameter were passed

through a mechanical grinder (Fig.3.2b) mounted with two parallel iron cylinders rotating

mechanically and crushed the material to further finer fractions. Two mechanical sieves

(Fig.3.2c) having pore size 2 and 4 mm diameter, respectively were used to separate

calcium carbide particles of about 2-4 mm diameter. For matrices formation powdered

29

calcium carbide was obtained by passing ground material through a sieve having pore

size about 200µm.

Fig. 3.2 (a) Mechanical hammer, (b) Fine grinder and (c) Mechanical sieve

3.3.1.2 Encapsulation of calcium carbide

Powdered calcium carbide was encapsulated in a way as described in section

3.1.6.

3.3.1.3 Bee-wax coating

Calcium carbide particles of 2-4 mm diameter and commercial grade bee-wax of

local origin were weighed in 4:6 ratios, respectively. Bee-wax was melted in a drum

shape container, mechanically rotating over flame and calcium carbide was added to it.

The container was provided with two parallel flippers (Fig.3.3) on inner side to ensure

complete mixing of melted wax with calcium carbide particles. After complete mixing

flame was off but rotation was continued till the drum was cooled up to 50 to 60 Cº. After

that material was poured out on a paper sheet having sufficient amount of plaster of paris

spreaded over. Wax coated calcium carbide then mixed with plaster of paris by gentle

manual rubbing to keep particles separate from each other. Excess plaster of paris (not

stick to wax coated particles) was sieved out and material was weighed again. Final

composition of wax coated CaC2 was recorded as 38% calcium carbide, 49% bee-wax

and 13% plaster of paris.

30

Fig. 3.3 Inner surface of drum

3.3.1.4. Paraffin-wax coating

Calcium carbide was coated with paraffin wax according to the procedure as

described in case of bee wax coating in section 3.3.1.3.

Fig. 3.4 Wax coated CaC2

3.3.1.5 Paint coating

Calcium carbide, 2-4 mm diameter particles and black enamel paint were weighed

in 4:6 ratios, respectively and mixed in a drum shape container, rotating mechanically by

fallowing similar procedure as described in section 3.3.1.3. Final composition of paint

coated CaC2 was recorded as 35 % calcium carbide, 44 % black enamel paint and 21 %

plaster of paris.

3.3.1.6 Matrices formation

Matrix-I (21 % calcium carbide, 58 % polyethylene and 21 % plaster of paris),

matrix-II (42 % calcium carbide, 48 % polyethylene and 10 % plaster of paris) and

matrix-III (61 % calcium carbide, 34 % polyethylene and 5 % paraffin oil) were prepared

by mixing powdered calcium carbide (about < 200 µm diameter) and plaster of paris or

paraffin oil with molten polyethylene in a rotator mixer as described in section 3.3.2.

After complete mixing matrices were poured out on a paper sheet and allowed to cool

31

down. The clumps then cut into 4 mm diameter particles and dipped into paraffin oil to

block the cut ends.

Fig.3.5 Matrix-I

3.3.2 Soil preparation Soil was collected from the same field as in case of experiment 1 and prepared

and analyzed as described in sections 3.1.2 and 3.1.3, respectively.

3.3.3 Application of fertilizer Ammonium sulphate fertilizer @ 1 g kg-1 soil was mixed thoroughly with the soil.

3.3.4 Bottle filling The 1000 ml capacity polyethylene plastic bottles were filled with fertilized soil

@ 500 g per bottle. The caps of these bottles were fitted with rubber septa for gas

sampling (Fig.3.7).

Fig.3.6 Experimental bottle with rubber septum

3.3.5 Treatment plan

Calcium carbide @ 22.5 mg kg-1 soil in the form of different formulations was

placed in the bottles before soil filling, according to the following treatment plan:

T1 = Control (no calcium carbide)

32

T2 = Encapsulated calcium carbide

T3 = Bee wax coated calcium carbide

T4 = Paraffin wax coated calcium carbide

T5 = Enamel paint coated calcium carbide

T6 = Matrix-I

T7 = Matrix-II

T8 = Matrix-III

Above describe calcium carbide formulations were already used by Banerjee and

Mosier (1989), Freney et al. (2000) and Yaseen et al. (2006) as nitrification inhibitors.

Calcium sulfate was added to adjust the amount of calcium added from CaC2 in

the treatments where CaC2 was not applied.

3.3.6 Incubation conditions Bottles were arranged according to completely randomized design with three

replications in an incubator at 25 ˚C for 91 days.

3.3.7 Moisture content maintenance Moisture level at 60% of water holding capacity was maintained throughout the

experiment.

3.3.8 Gas sampling Gas samples were taken after 3 and 7 days and then with two weeks interval up to

91 days. For acetylene and ethylene detection, sampling bottles were closed with gas

tight caps fitted with rubber septa for 24 hours and headspace air samples were taken

with the help of a gas tight syringe fitted with hypodermic needle 12 and 24 hours after

closing the bottles.

3.3.9 Analysis for acetylene and ethylene contents Acetylene (C2H2) and ethylene (C2H4) content were determined from gas sample

using Gas Chromatograph (Shimadzu GC 2010) fitted with flame ionization detector

(FID) and a capillary column (Porapak Q 80-100) operating isothermally under the

following conditions: Carrier gas, N2 (13 ml min-1); H2 flow rate, 33 ml min-1; Air flow

rate, 330 ml min-1; Sample volume 1 ml; Column temperature 70 ˚C. The acetylene and

33

ethylene concentrations were determined by comparison with reference standards of C2H2

and C2H4 (99.5 %) obtained from Matheson (Secancus, NJ).

3.3.10 Acetylene and ethylene flux Acetylene and ethylene flux was calculated by using following formula (Rolston,

1986).

V C F = ----------

A t Where

F = Gas flux (ng m-2 min-1)

V = Volume of head space (3.97 × 10-4 m3)

A = Area of soil surface in the bottle (5.67 × 10-3 m2)

C/ t= Change in gas concentration per unit time (ng min-1)

3.3.11 Soil sampling A cylindrical core soil sampler of 10 mm diameter was used to sample soil from

plastic bottles. Soil was sampled after 3 and 7 days and then with 2 weeks interval and

sampling hole in bottle soil was filled with same amount of soil from a fourth replication

(not included in statistical analysis).

3.3.12 Soil analysis for nitrate-N and ammonium-N concentrations For nitrate-N and ammonium-N determination, 10 g soil was extracted by using 2

M KCl as extracting solution in a 1:5 (soil: water) ratio. Ammonium (NH4+-N) and

nitrate (NO3--N) plus nitrite (NO2

--N) were determined by steam distillation of ammonia

(NH3), using heavy MgO for NH4+-N and Devarda's Alloy for NO3

--N (Bremner and

Keeney, 1965). The distillate was collected in saturated H3BO3 and titrated to pH 5.0

with dilute H2SO4 (Buresh et al., 1982; Keeney and Nelson, 1982).

3.4 Experiment 4 This experiment was comprised of two trials viz. 4(A) and 4(B). The detailed

methodology of these experiments is given in the following pages.

34

3.4.1 Experiment 4(A) Effect of Calcium Carbide Based Formulations on Seed Germination, Seedling Growth and Root:Shoot Ratio of Wheat (Laboratory Trial)

This trial was conducted in sand medium. Sand was sieved, repeatedly washed

with distilled water, dried up to field capacity and filled into plastic cups (7 cm in length

and 5 cm in diameter) @ 450 g cup-1.

3.4.1.1 Seed sowing

Three seeds of wheat cv. Inqulab-91 per cup were sown at 1 cm depth. To assure

the same sowing depth in all the treatments, seeds were placed on leveled sand surface in

the cups and exactly 1 cm thick sand layer was spread over the seeds.

3.4.1.2 Treatment plan

Calcium carbide @ 22.5 mg kg-1 sand was placed in the plastic cups before sand

filling according to the following treatment plan:

T1 = Control (no calcium carbide)

T2 = Encapsulated calcium carbide

T3 = Bee wax coated calcium carbide

T4 = Paraffin wax coated calcium carbide

T5 = Enamel paint coated calcium carbide

T6 = Matrix-I

T7 = Matrix-II

T8 = Matrix-III

Calcium sulfate was added to non calcium carbide treatments to adjust amount of

calcium added from CaC2.

3.4.1.3 Experimental design

Four cups were considered as one experimental unit to observe emergence of

seedlings. Cups were arranged according to completely randomized design with three

replications.

35

3.4.1.4 Calculation of mean emergence time and emergence rate index

Seed germination and seedling emergence were observed on daily basis and mean

emergence time (MET) and emergence rate index (ERI) were calculated by using the

following formulae:

N1T1 + N2T2 + …………NnTn MET = ---------------------------------------

N1 + N2 + ………………..Nn

and

Ste ERI = --------

MET Where

MET = Mean emergence time

N1-n = Number of seedling emerging since the time of previous count

T1-n = Number of days after sowing

Ste = Number of total emerged seedling per experimental unit

ERI = Emergence rate index

3.4.1.5 Fresh biomass weight

One cup from each replication was selected randomly after 3, 6, 12 and 15 days of

sowing. The selected cups were washed under tap water to remove sand from the plants

and fresh biomass weight plant-1 was determined.

3.4.1.6 Root : Shoot ratios

Fifteen days after sowing, sand was separated from plants by washing with tap

water and plants were cut into roots and shoots. Roots and shoots were weighed

separately on electrical balance, root and shoot length was measured and root : shoot

ratios by weight and length were calculated.

36

3.4.2 Experiment 4(B) Effect of Different Doses of Matrix-I Based Calcium Carbide on Wheat Seedling Emergence (Pot Trial)

Matrix-I formulation of calcium carbide was found the best among all the

formulations from experiment 4(A). This formulation was then used for further

experimentation regarding wheat seed germination and seedling emergence.

Site of the experiment, soil preparation, soil analysis and pot filling were the same

as described in sections from 3.1.1 to 3.1.4.

3.4.2.1 Seed sowing Twelve seeds per pot were sown 1 cm deep at equal distance in the pots. To

maintain uniform seed sowing depth, seeds were placed on well leveled pot soil and

exactly 1 cm soil layer were spread over the seeds.

3.4.2.2 Calcium carbide application

Calcium carbide was applied as matrix-I formulation @ 0, 7.5, 15, 22.5 mg kg-1

soil at 4 cm depth in the centre of pot immediately after seed sowing.

3.4.2.3 Mean emergence time and emergence rate index

Emergence of wheat seedlings was observed on daily bases and mean emergence

time and emergence rate index was calculated as described in section 3.4.1.4.

3.5 Experiment 5 Effect of Calcium Carbide Based Formulations on Growth, Yield and Nitrogen Uptake of Wheat (Pot Trial)

This experiment was conducted to select the best calcium carbide formulation out

of seven, with respect to growth and yield parameters of wheat. Site of the experiment,

soil preparation, soil analysis, pot filling and layout of the experiment from seed sowing

to maturity were the same as described in experiment 1 in sections from 3.1.1 to 3.1.5,

respectively.

37

3.5.1 Treatment plan Pots were arranged according to completely randomized design with 3

replications. Calcium carbide @ 22.5 mg kg-1 soil was applied two weeks after sowing

(best rate and time of ECC application as illustrated from the results of exp.1 and 2,

respectively), in the centre of pot at 4 cm depth according to the following treatment plan:

T1 = Recommended dose of P&K, alone

T2 = Recommended dose of NPK, alone

T3 = NPK + Encapsulated calcium carbide

T4 = NPK + Bee wax coated calcium carbide

T5 = NPK + Paraffin Wax coated calcium carbide

T6 = NPK + Enamel paint coated calcium carbide

T7 = NPK + Matrix-I

T8 = NPK + Matrix-II

T9 = NPK + Matrix-III

Calcium sulfate was added to non calcium carbide treatments to adjust amount of

calcium added from CaC2.

3.5.2. Parameters studied Plant height, number of tillers per pot, root weight, biological yield, straw yield,

grain yield and N concentration and uptake by different plant parts were studied during

growth period or at final harvest following the procedures described in section 3.1.8.

Methodology for the determination of some other parameters is explained under the

following headings.

3.5.2.1 Thousand grains weight

Thousand grains were counted from each pot and their weights were taken with a

digital electrical balance Model A&D GR-200 (Made in Japan).

3.5.2.2 Soil mineral nitrogen

Soil was sampled from each pot with a core sampler of 10 mm diameter, 8 weeks

after calcium carbide application (at booting stage of crop) and was analyzed for nitrate-

N and ammonium-N according to the procedure described in section 3.3.12.

38

3.6 Experiment 6 Effect of Rate and Application Depth of Matrix-I Calcium Carbide Based Formulation on Growth, Yield and Nitrogen Uptake of Wheat (Pot Trial)

Pot trial was conducted to evaluate the effect of calcium carbide in the

form of matrix-I (performed the best in pot experiment 5), applied at different

soil depths, on growth and yield and N uptake of wheat.

Site of the experiment, soil preparation, soil analysis, pot filling and agronomic

practices from seed sowing to maturity were the same as described in experiment 1 in

sections from 3.1.1 to 3.1.5, respectively.

3.6.1. Treatment plan The pots were arranged according to completely randomized design

(CRD) 2 factor factorial with 4 replications. Calcium carbide in the form of

matrix-I was applied two weeks after sowing under the following treatment plan.

3.6.1.1 Rate of application of calcium carbide (Factor A)

Matrix-I formulated calcium carbide was applied @ 0, 7.5, 15 and 22.5 mg kg-1

soil. These rates were chosen on the bases of the results of preliminary trials.

3.6.1.2 Depth of application of calcium carbide (Factor B)

Calcium carbide was added at 0, 4, 8 and 12 cm depth in the centre of pot.

Calcium sulfate was added to non calcium carbide treatments to adjust calcium added

from CaC2.

3.6.2. Parameter studied Plant growth and yield related parameters and some analytical parameters were

studied according to the procedures as described in sections 3.1.8 and 3.5.2.

39

3.7 Experiment 7 Response of Wheat to Soil Applied Matrix-I Formulated Calcium Carbide with and without Nitrogen Fertilizer (Pot Trial)

Pot trial was conducted to evaluate the performance of matrix-I

formulated calcium carbide with and without different doses of nitrogen fertilizer

on growth, yield and N uptake of wheat. Site and conditions of the experiment, soil

preparation, soil analysis, pot filling, layout out of the experiment and agronomic

practices from seed sowing to maturity were the same as described in experiment 1 in

sections from 3.1.1 to 3.1.5, respectively.

3.7.1. Treatment plan The pots were arranged according to completely randomized design

(CRD) 2 factor factorial with 4 replications. Calcium carbide in the form of

matrix-I was applied two weeks after sowing at 8 cm depth under the following

treatment plan.

3.7.1.1 Rate of N fertilizer application (FactorA)

Nitrogen fertilizer was applied at zero (control), half (30 mg kg-1 soil) and

full recommended rate (60 mg kg-1 soil).

3.7.1.2 Rate of calcium carbide application (Factor B)

Matrix-I formulated calcium carbide was applied @ 0, 7.5, 15 and 22.5 mg kg-1

soil.

Matrix-I coated calcium sulfate was added to non calcium carbide treatments to

adjust amount of calcium added from CaC2.

3.7.2 Parameter studied Growth and yield related parameters and some analytical parameters were studied

according to the procedures as described in sections 3.1.8 and 3.5.2. Effect of calcium

carbide on spike related parameters of wheat was also studied according to the

procedures as described below.

40

3.7.2.1 Spike length

Spike length (cm) was measured with the help of ruler and mean was

calculated from each pot.

3.7.2.2 Number of spikelets spike-1

Number of spikelets spike-1 was counted and mean was calculated from

each pot.

3.7.2.3 Number of grains spike-1

Spikes from each pot were threshed manually, grains were counted and mean was

calculated.

3.8 Experiment 8 Growth and Yield Response of Wheat to Soil Applied Calcium Carbide under Field Conditions

3.8.1 Type of experiment The experiment was conducted on farmer’s field at Chak No. 388 J.B, Toba Tek

Singh in 2006-2007 to evaluate the effect of rate of calcium carbide applied in different

formulations on two wheat varieties i.e Inqulab-91 (medium stature) and Bhakhar-2002

(tall stature). The experiment was repeated in 2007-2008 with the same layout plan and

on the same field.

3.8.2 Date of sowing and harvesting of wheat crop Wheat varieties were sown on 15th November, 2006 and harvested on 24 April,

2007. The same experiment with same layout was repeated in 2007-08 where wheat

varieties were sown on 12th November, 2007 and harvested on 16th April, 2008.

3.8.3 Treatment plan In both the years plot size was maintained as 4 m x 4.5 m and experiment was

conducted under randomized complete block split-split plot design with three

replications. Two wheat varieties Inqulab-91 and Bhukhar-2002 were sown and three

CaC2 formulations i.e paint coated calcium carbide, matrix-I and matrix-II were applied

@ 0, 15, 30 and 45 kg ha-1 CaC2. Wheat varieties, calcium carbide formulations and rates

41

of CaC2 were allotted to main plot, split plot and split split plot, respectively. The detailed

layout plan of the experiment is presented in Table 3.2.

3.8.4 Soil physical and chemical analysis Procedures described in section 3.1.3 were followed for soil physical and

chemical analysis. Soil characteristics are presented in Table 3.3.

3.8.5 Application of fertilizers Nitrogen, phosphorus and potassium were applied at recommended rate of 120-

90-60 kg ha-1 in the form of fertilizers urea, DAP and SOP, respectively. All P and K

added to the soil at sowing time. Nitrogen was applied in two splits i.e. half at sowing

time and remaining half dose after two weeks of sowing with 1st irrigation. At sowing

time fertilizers were applied through broadcast during seedbed preparation and

incorporated with ploughing and planking. Second dose of nitrogen fertilizer was applied

with irrigation water.

3.8.6 Application of calcium carbide Matrix-I, matrix-II and paint coated calcium carbide were applied @ 0, 15, 30 and

45 kg CaC2 ha-1 two weeks after seed sowing. Holes, 8 cm deep and 30 cm apart were

made with the help of a steel rod and weighed amount of calcium carbide was uniformly

distributed to the holes of a specific plot. After calcium carbide application holes were

plugged manually with soil.

3.8.7 Parameters studied Same parameters were studied in both the years and average of two years was

used in statistical analysis.

3.8.7.1 Plant height

At maturity twenty plants were selected at random from each plot at 3 places,

their heights were measured in cm and means were calculated.

3.8.7.2 Number of tillers and spikes

An area of 1 m2 was selected at random at 3 places in each plot to count total

number of tillers at the completion of tillering stage and number of spikes at maturity,

average was used in the statistical analysis.

42

3.8.7.3 Biological yield and grain yield

Whole plots were harvested and tied into bundles. Biological yield was recorded

by weighing the bundles of each plot with spring balance. The bundles were first sun-

dried and then threshed by a thresher. The grain weight was recorded in kg and then

converted into kg ha-1.

3.8.7.4 Lodging index

Before harvesting, lodging index was calculated by using following relation

(Simmons et al., 1988).

Lodging index = Intensity score × Area score × 0.2

Where:

Intensity score ranges from 1 (erect) to 5 (flat) and

Area score ranges from 1 (no lodging) to 9 (total lodging).

Thus lodging index ranges from 0.2 (no lodging) to 9.0 (total area flat).

3.8.7.5 Soil mineral nitrogen

For soil mineral nitrogen (nitrate-N and ammonium-N) soil was sampled 8 weeks

after calcium carbide application from 0 to 6 cm depth. Soil nitrate-N and ammonium-N

were determined according to the same procedure as described in 3.2.12. Samples were

stored at freezing temperature until analyzed.

3.9.7.6 Other parameters

1000-grains weight, straw yield, N concentration and uptake of wheat grain and

straw were determined by the same procedures as described in sections 3.1.8 and 3.5.2.

3.9 Statistical analysis Data of all the experiments were subject to ANOVA using MSTAT-C (1991)

software package. Least Significant Difference (LSD) test was used to determine the

differences among the treatment means (P = 0.05).

43

Table 3.1 Physico-chemical characteristics of soil used in laboratory and pot trials.

Parameters Value Characteristics Value

Sand 50.86 % CO3 - - Absent

Silt 27.74 % HCO3- 0.9 meq L-1

Clay 21.40 % Cl⎯ 14.7 meq L-1

Texture class Sandy clay loam SO4 -- 9.1 meq L-1

Saturation %age 31.0 % Na+ 14.1 meq L-1

pHs 7.85 Ca++ + Mg++ 8.38 meq L-1

ECe 2.53 dS m-1 Total nitrogen 0.032 %

CEC 4.38 cmolc kg-1 soil Available phosphorus (P) 6.55 mg kg-1 soil

Organic matter 0.62 % Extractable Potassium (K) 170 mg kg-1 soil

44

Table 3.3 Physico-chemical characteristics of farmer’s field soil at Toba Tek Singh.

Parameters Value Parameters Value

Sand 39.32 % CO3 -- 0.58 meq L-1

Silt 29.54 % HCO3- 0.92 meq L-1

Clay 31.11 % Cl⎯ 16.8 meq L-1

Texture class Clay loam SO4 -- 8.5 meq L-1

Saturation %age 35.0 % Na+ 15.2 meq L-1

pHs 7.92 Ca++ + Mg++ 7.5 meq L-1

ECe 2.78 dS m-1 Total nitrogen 0.03 %

CEC 4.75 cmolc kg-1 soil Available phosphorus (P) 6.21 mg kg-1 soil

Organic matter 0.53 % Extractable Potassium (K) 510 mg kg-1 soil

45

Table 3.2 Layout plan of experiment 8.

V1F1C1 V1F2C2 V1F3C1 V2F3C4 V2F2C3 V2F1C1 V1F2C1 V1F3C4 V1F1C1

V1F1C4 V1F2C4 V1F3C3 V2F3C3 V2F2C2 V2F1C2 V1F2C3 V1F3C1 V1F1C3

V1F1C3 V1F2C3 V1F3C2 V2F3C2 V2F2C4 V2F1C3 V1F2C2 V1F3C3 V1F1C2

V1F1C2 V1F2C1 V1F3C4 V2F3C1 V2F2C1 V2F1C4 V1F2C4 V1F3C2 V1F1C4

V2F1C2 V2F3C4 V2F2C1 V1F1C1 V1F3C4 V1F2C1 V2F2C3 V2F1C4 V2F3C1

V2F1C3 V2F3C2 V2F2C3 V1F1C3 V1F3C1 V1F2C2 V2F2C2 V2F1C1 V2F3C2

V2F1C1 V2F3C3 V2F2C2 V1F1C2 V1F3C3 V1F2C3 V2F2C1 V2F1C3 V2F3C3

V2F1C4 V2F3C1 V2F2C4 V1F1C4 V1F3C2 V1F2C4 V2F2C4 V2F1C2 V2F3C4

V1= c.v. Inqulab-91; V2= c.v. Bhakhar-2002. F1= matrix-I; F2= matrix-II; F3= paint coated CaC2. C1, C2, C3 and C4 = Calcium carbide @ 0, 15, 30 and 45 kg ha-1, respectively

CHAPTER 4 RESULTS AND DISCUSSION

The results of a series of experiments conducted in laboratory, wirehouse and

field, to evaluate calcium carbide as a potent source of acetylene (nitrification inhibitor

gas) and ethylene (plant growth hormone) and its effect on growth, yield and nitrogen use

efficiency of wheat crop are described in detail here.

4.1 Experiment 1 Effect of Rate of Encapsulated Calcium Carbide on Growth, Yield and Nitrogen Uptake of Wheat (Pot Trial)

4.1.1 Introduction Nitrogen recovery by crop plants grown under flooded or un-flooded soil

conditions seldom exceeds 40 % (Sharma and Yadav, 1996). The main transformation

processes involved in reducing N recovery are ammonia volatilization, nitrification,

denitrification and leaching. In alkaline and calcareous soils about 70 % of applied N is

lost through these processes (Hazarik and Sarkar, 1996). It is a common problem of

Pakistani agriculture that about 35 % of N fertilizer applied through broadcast over the

soil surface is volatilized. The ammonia volatilization can be checked by shifting N

fertilizer application method from broadcast to incorporation or deep placement

(Keerthisinghe et al., 1996). However, incorporation or deep placement of nitrogen

fertilizer increases the fertilizer contact with the soil and soil microbes which results in

conversion of ammonium to nitrate through nitrification process. Nitrate being negatively

charged ion can easily leaches down to lower soil layers. Nitrate also goes through

denitrification process and transforms to N2O or N2. These transformations ultimately

results in low N recovery efficiency (Keerthisinghe et al., 1996). Thus it is the need of

time to enhance N recovery by incorporation of N fertilizer deep into the soil and to

inhibit nitrification with some nitrification inhibitor. It is also become necessary because

fertilizers are now become energy consuming costly inputs.

Calcium carbide as a source of acetylene is a powerful nitrification inhibitor under

both flood and non-flood soil conditions (Freney et al., 1990; Keerthisinghe et al., 1996;

Sharma and Yadav, 1996; Randall et al., 2001; Ahmad et al., 2004). It inactivates

ammonia mono-oxigenase enzyme which is involved in conversion of ammonium to

nitrate in the soil (Freney et al., 1990; Randall et al., 2001). Moreover acetylene released

from CaC2 is converted into plant hormone ethylene (C2H4) by soil microorganisms

(Muromtsev et al., 1988; Lurssen 1991; Arshad and Frankenberger, 2002). Ethylene

plays major role in growth and development processes of plants by stimulating seed

germination, shoot and root growth and early crop maturity (Arshad and Frankenberger,

2002). So both C2H2 and C2H4 may be regarded as potent nitrification inhibitor and

growth stimulator (Freney et al., 1990; Arshad and Frankenberger, 2002). This study was

carried out to find out appropriate dose of encapsulated calcium carbide to improve

growth, yield and nitrogen uptake by wheat.

4.1.2 Materials and Methods

Methodology of the experiment is described in section 3.1 in Materials and

Methods chapter.

4.1.3 Results and Discussion

4.1.3.1 Results

4.1.3.1.1 Plant height

Data regarding effect of rate of encapsulated calcium carbide (ECC) on plant

height (cm) of wheat is presented in Fig.4.1. Minimum Plant height (70.2 cm) was

observed in control and maximum (76.9 cm) in treatment where nitrogen @ 60 mg kg-1

soil was applied without calcium carbide. Wheat plant height was decreased with

increasing rate of ECC (Fig.4.3). Treatments including calcium carbide application of

22.5, 30 and 37.5 mg kg-1 soil were statistically at par in reducing plant height.

Comparison among treatments with nitrogen fertilizer @ 60 mg kg-1 soil, maximum

reduction in plant height was observed where ECC @ 37.5 mg kg-1 was applied.

4.1.3.1.2 Number of tiller pot-1

Tillering is one of yield contributing growth parameters. Normally more the

number of tillers per plant more will be grain yield. It is particularly true when fertile

tillers are increased in number.

Effect of rate of ECC on number of tillers pot-1 of wheat is presented in Fig.4.2.

About 48 % more number of tillers per pot was observed with nitrogen fertilizer

application than without it. It is also evident from the data (Annexure I) that number of

tillers pot-1 was increased with the application of ECC. Compared to fertilizer alone,

calcium carbide application increased number of tillers by 24 %. Minimum number of

tillers (11) was observed in control and maximum (27) where calcium carbide was

applied @ 22.5 mg kg-1 soil with 60 mg kg-1 fertilizer nitrogen.

It was also observed that reduction in plant height and increase in number of

tillers of wheat due to calcium carbide application change the physical appearance of

wheat plants in pots from erect to somewhat bushy (Fig. 4.3).

4.1.3.1.3 Root weight

Data on effect of rate of ECC on root weight of wheat (Fig. 4.4) revealed that the

application of fertilizer nitrogen in combination with ECC significantly improved root

weight per pot compared to that in control. Minimum root weight (5.8 g) was observed in

control while it was maximum (11.1 g) in the treatment where ECC (22.5 mg kg-1 soil)

plus fertilizer nitrogen (60 mg kg-1 soil) was applied. Root weights in treatments with

ECC application @ 22.5 and 30 mg kg-1 soil were statistically similar. However,

reduction in root weight of wheat was observed where ECC was applied @ 37.5 mg kg-1

soil compared to that of treatments with ECC @ 22.5 or 30 mg kg-1 soil.

4.1.3.1.4 Straw yield

A pronounced effect of different doses of ECC on straw yield (g pot-1) of wheat is

obvious from data (Fig.4.5). Nitrogen application significantly increased straw yield

compared to control. ECC application further improved straw yield of wheat and

maximum straw yield (38.7 g) was observed where calcium carbide was applied @ 22.5

mg kg-1 soil. Straw yield in treatments with ECC @ 30 mg kg-1 soil was statistically at

par compared to that of 22.5 mg kg-1 soil. It was also observed that in treatments where

ECC was applied @ 7.5, 15 and 37.5 mg kg-1 soil with nitrogen fertilizer produced

statistically similar straw yield compared to that of fertilizer alone, indicating that

application of ECC at these rates had no effect on straw yield of wheat.

4.1.3.1.5 Grain yield

Effect of application of nitrogen fertilizer with and without different doses of

encapsulated calcium carbide on grain yield of wheat is quite different than that of straw

as is clear from data in Fig.4.6. Statistically more grain yield (g pot-1) was observed in the

treatment where nitrogen fertilizer was applied alone than without it (control). However,

ECC application significantly further increased grain yield of wheat compared to

fertilizer alone. Maximum grain yield (26 % more than that of fertilizer alone treatment)

was observed where ECC was applied @ 22.5 mg kg-1 soil with nitrogen fertilizer.

Similar grain yield production was observed in treatments where calcium carbide was

applied @ 7.5, 15 and 37.5 mg kg-1 soil. Moreover, grain yield with ECC @ 30 mg kg-1

soil was statistically at par compared to that of ECC @ 22.5 mg kg-1 soil.

4.1.3.1.6 Total nitrogen uptake

Increase in nitrogen uptake of wheat (straw + grains) was observed with nitrogen

fertilizer application alone however ECC further improved nitrogen accumulation in plant

parts (Fig.4.7). Maximum nitrogen uptake was observed in the treatment of calcium

carbide application of 22.5 mg kg-1 soil which was statistically at par compared to that of

with ECC @ 30 and 37.5 mg kg-1 soil. ECC application @ 7.5 mg kg-1 soil did not effect

total N uptake by wheat compared to that of fertilizer alone treatment.

4.1.3.2 Discussion

Calcium carbide is well known as a ripening material (Vrebalov et al., 2002;

Barry et al., 2005). It is also well documented as a potent source of acetylene gas, a

nitrification inhibitor gas (Freney et al., 2000) which is then converted into ethylene gas

in soil, a potent hormone, by soil microorganisms (Yaseen et al., 2006). Due to this

bifacet function of calcium carbide, Russian used calcium carbide based formulation to

improve yield and quality of vegetables, fruits and other crops (Muromstev et al., 1988).

These facts about calcium carbide and results of liquid source of ethylene (Ethephon-

ethylene releasing liquid compound) on all kinds of crops got attention of scientists to

explore its more function/role in plant growth by making economical formulations. It is

also a need of time to use non conventional approaches in combination with conventional

one to improve crop yields to feed ever increasing population.

This experiment was conducted to find right rate of calcium carbide for improving

growth and yield of wheat. Results of this study indicate that application of CaC2 at

appropriate rate with recommended dose of NPK fertilizers significantly increased grain

yield of wheat. It reduced the plant height due to stimulatory effect of ethylene on early

root growth. Cooke et al. (1983) reported the involvement of stem shortening PGR

ethephon in root growth and development. Healthy root growth actively absorbed more

nutrients from the soil to enhance tillering. Many workers have already reported that

production of acetylene/ethylene in rhizosphere stimulates tillering (Freney et al., 1990;

Sharma and Yadav, 1996; Randall et al., 2001; Ahmad et al., 2004).

Increased yield of wheat grain with the application of CaC2 is attributed to

enhanced uptake of nutrients by wheat due to production of ethylene from CaC2. It may

be due to increase in root primordia to explore more volume of soil to acquire nutrients

(Ahmad et al., 2004). Enhanced N uptake by grains due to calcium carbide application

may be due to nitrification inhibitory effect of acetylene released from CaC2 that could

improve the N economy of soil which is very much required as soils of Pakistan are

deficient in nitrogen. Overall, results show that all growth and yield related parameters

were improved with the application of ECC @ 22.5 mg kg-1 soil. Therefore, this rate of

application of CaC2 is considered the best and used for exploration of its effects in further

experiments on wheat.

4.2 Experiment 2 Effect of Time of Application of Encapsulated Calcium Carbide on Growth, Yield and Nitrogen Uptake of Wheat (Pot Trial)

4.2.1 Introduction Encapsulated calcium carbide (ECC) when applied to soil releases nitrification

inhibitor gas ‘acetylene’ which is converted to plant hormone ‘ethylene’ by soil microbes

(Muromtsev et al., 1988; Arshad and Frankenberger, 2002). Both the gases have

pronounced influence on pant growth from germination to maturity and thus influence the

yield and yield contributing parameters (Bronson et al., 1992; Freney et al., 1992a;

Ahmad et al., 2004).

Being a plant hormone, ethylene stimulates or inhibits a number of growth

processes and thus time of application of some ethylene source like encapsulated calcium

carbide may be an important factor to control plant growth and development. Results of

experiment 1 revealed that application of ECC @ 22.5 mg kg-1 soil was the best one

among all the doses of calcium carbide. At this rate of application of ECC, almost all

yield contributing parameters were maximum. After finding out the best rate of

application of ECC, now question arises at what growth stage it should be applied. In this

study the encapsulated calcium carbide was applied at three different times in the

presence of recommended dose of nitrogen fertilizer to know the best time of ECC

application for better growth and yield of wheat.

4.2.2 Materials and Methods Methodology of the experiment is described in section 3.2 in Materials and

Methods chapter.

4.2.3 Results and Discussion

4.2.3.1 Results

Results of this experiment are described here on different plant growth and yield

parameters after the application of best rate of ECC (found out from the findings of

experiment 1) at three growth stages i.e. at sowing, 2 and 4 weeks after sowing.

4.2.3.1.1 Plant height

Data regarding effect of time of application of encapsulated calcium carbide on

plant height (cm) of wheat is presented in Fig.4.8. Minimum plant height was observed in

control and maximum in treatment where nitrogen fertilizer @ 60 mg kg-1 soil was

applied. Encapsulated calcium carbide applied at either time with nitrogen fertilizer

significantly reduced plant height. In nitrogen fertilized treatments maximum reduction in

plant height was observed with application of ECC @ 22.5 mg kg-1 soil 2 weeks after

sowing.

4.2.3.1.2 Number of tillers pot-1

Increase in number of tillers pot-1 of wheat was observed with the application of

nitrogen fertilizer compared to control (Fig.4.9). Encapsulated calcium carbide

application to N fertilized pots further enhanced number of tillers. According to an

estimate, 33 % more tillers were produced when ECC @ 22.5 mg kg-1 soil was applied 2

weeks after sowing with recommended rate of nitrogen fertilizer compared to nitrogen

fertilizer application alone.

4.2.3.1.3 Root weight

It is evident from the data (Fig.4.10) that ECC application significantly affected

root weight (g pot-1) of wheat. About 51 % more root weight was observed where ECC @

22.5 mg kg-1 soil was applied at sowing or 2 weeks after sowing along with nitrogen

fertilizer @ 60 mg kg-1 soil than that of nitrogen fertilizer alone. ECC application at 4

weeks after sowing did not affect root weight of wheat compared to that of N fertilizer

alone.

4.2.3.1.4 Straw yield

Data regarding effect of time of application of encapsulated calcium carbide on

straw yield (g pot-1) of wheat is presented in Fig.4.11. It is revealed from data that more

straw yield was produced with the application of nitrogen fertilizer than control.

However, ECC application further improved straw yield of wheat. Maximum straw yield

was observed in the treatment where ECC @ 22.5 mg kg-1 soil was applied 2 weeks after

sowing. Straw yield of treatment with ECC applied 4 weeks after sowing was statistically

at par compared to its application 2 weeks after sowing. Least effect on straw yield of

wheat was observed with ECC when it was applied at sowing compared to its application

2 weeks after sowing.

4.2.3.1.5 Grain yield

Encapsulated calcium carbide application significantly affected grain yield (g pot-

1) of wheat (Fig.4.12). Minimum grain yield was observed in control (T1) and maximum

in the treatment where N fertilizer was applied with ECC @ 22.5 mg kg-1 soil at 2 weeks

after sowing. Application of ECC produced about 30 % more grain yield when applied @

22.5 mg kg-1 soil at 2 weeks after sowing in combination with nitrogen fertilizer

compared to fertilizer alone. Encapsulated calcium carbide affected the grain yield of

wheat in a similar way when applied at sowing or 4 weeks after sowing but extent of

effect was relatively less compared to that when applied at 2 weeks after sowing.

4.2.3.1.6 Total nitrogen uptake

Data regarding effect of time of ECC application on nitrogen uptake (straw +

grain) of wheat is summarized in Fig.4.13. It is revealed from data that calcium carbide

application significantly affected nitrogen accumulation in wheat plant parts. Wheat

straw and grain took up more nitrogen from nitrogen fertilizer applied pots than that in

control (T1). Further increase in N uptake of wheat was observed where ECC was

applied along with nitrogen fertilizer. Regarding total nitrogen uptake, more obvious

results were observed where ECC was applied 2 weeks after sowing compared to its

application at sowing or 4 weeks after sowing.

4.2.3.2 Discussion

Calcium carbide plays dual role i.e. as a nitrification inhibitor and plant growth

regulator and both these rules are well documented by many scientists (McCarty and

Bremner, 1986; Muromtsev et al., 1988; Muromtsev et al., 1993; Freney et al., 1993;

Bibik et al., 1995). Now it is needed to know its right dose and right time of application

because its higher doses can affect plant growth adversely.

Results of the experiment are evident that encapsulated calcium carbide (ECC)

application to nitrogen fertilized pot significantly reduced plant height and increased

number of tillers, root weight, straw and grain yield and nitrogen uptake of wheat. The

effect of ECC on plant growth and yield parameters of wheat is owing to the acetylene

and ethylene gases produced from calcium carbide in the soil environment. Decrease in

plant height with calcium carbide application is a typical response of cereals to ethylene

and may be due to more photosynthate translocation towards plant roots as ECC

application significantly enhanced root weight. Secondly ethylene is involved in

changing the orientation of the cortical microtubule array of the cell and resultantly cells

grow more in lateral direction than longitudinal and thus resulted in reduction in plant

height (Alberts et al., 1989). Decrease in plant height of cereals due to ethylene is also

reported by Dahnous et al. (1982), Wiersma et al. (1986), Rajala and Peltonen-

Sainio (2001), Rajala et al. (2002) and Mahmood et al. (2002). Healthy root

growth with calcium carbide application helps the plant to actively uptake more

nutrients from the soil to enhance tillering. Increase in number of tillers of

cereals due to acetylene/ethylene production in the rhizosphere has already been

reported by a number of research workers (Freney et al., 1990; Sharma and Yadav,

1996; Randall et al., 2001; Ahmad et al., 2004).

Increase in grain yield of wheat might be attributed to more number of tillers and

better root growth. It is an obvious fact that healthy and more roots can explore more soil

volume for nutrient uptake and thus ultimately give benefit to grain and/or straw yield

(Ahmad et al., 2004). The influence of nutrients on plant growth and development is well

documented. Increase in N uptake by wheat may be due to nitrification inhibition action

of ECC application. Acetylene released from calcium carbide in the soil environment

might inhibit nitrification and fertilizer nitrogen remained in plant available form for a

long time than usual.

It is revealed from the results of study that ECC improved wheat plant growth and

development better when applied 2 weeks after sowing compared to all other times of its

application. This might be due to the fact that after two weeks of sowing roots already

emerged out and are more active and better benefited with ethylene as well as nutrient

supply. It seems that ECC applied 4 weeks after sowing might not timely improve root

growth to uptake more nutrients to improve tillering. Moreover, almost all the tillering

has been completed till 4 weeks after sowing that is why application of ECC at this time

did not much influence the growth and yield parameters. Mahmood et al. (2005) reported

that application of ECC at time later than 2 weeks would lead only to increase the

size/boldness of grains in wheat.

4.3 Experiment 3 Evaluation of Different Type of Calcium Carbide Based Formulations for the Release of Acetylene and Ethylene Gases and Their Effect on Nitrification Inhibition under Laboratory Conditions

4.3.1 Introduction Nitrogen (N) losses through denitrification and nitrate leaching from the fertilized

soil can be checked by keeping N in ammonium form for a longer period of time through

the application of nitrification inhibitors (NI,s) (Hauck, 1983). A number of chemicals

have been reported to inhibit nitrification (Bundy and Bremner, 1973; Hauck, 1983;

Slangen and Kerkhoff, 1984), reduced the emission of N2O from soil and checked nitrate

leaching while applied with nitrogen fertilizers (Aulakh et al., 1984). Nitrapyrin is the

most commonly used and commercially available NI but its effectiveness is limited due

to sorption on soil colloids and volatilization (Keeney, 1983; Slangen and Kerkhoff,

1984).

It is reported that acetylene at partial pressures 0.1 to 10 pa inhibited the ammonia

mono-oxigenase enzyme which is responsible for the oxidation of ammonium to nitrate;

nitrification was inhibited even after the removal of acetylene up to seven days until the

enzyme was resynthesized by microbes (Berg et al., 1982). Acetylene is a gas and is

difficult to apply and maintain at a required concentration in the soil. McCarty and

Bremner (1986) tested a number of acetylene releasing compound for nitrification

inhibition and found that 2- ethynylpyridine and phenylacetylene successfully serve the

purpose. The effectiveness of these compounds was also confirmed by Freney et al.

(1993) under field conditions. But unfortunately, at present these compounds are too

expensive to use in agriculture.

A second approach has been researched out was to coat calcium carbide with wax

(Banerjee and Mosier, 1989), enamel black paint, filled in medical capsules (Yaseen et

al., 2006; Kashif et al., 2008) or mix with polyethylene (Freney et al., 2000) and slow its

reaction with water [CaC2 + 2H2O = C2H2 + Ca(OH)2] to produce acetylene in situ in

soil.

Acetylene released from calcium carbide not only inhibited nitrification (Bronson

and Mosier, 1991, 1992; Bronson et al., 1992; Freney et al., 1992a, 1993; Keerthisinghe

et al., 1993) but its reduction to ethylene by soil microbes is also reported (Bibik et al.,

1995; Yaseen et al., 2005, 2006; kashif et al., 2008). Ethylene is a plant growth hormone

and is involved in a number of physiological processes during plant growth and

development (Arshad and Frankenberger, 2002).

Keeping in view the above facts, there is need to find out some coating material

on CaC2 that can not only control/slow down the releases of gases in a specific time span

but also prolong and maintain its pressure in the soil. Present study was planned to assess

effectiveness of different coating materials to release gases slowly from the calcium

carbide.

4.3.2 Materials and Methods Methodology of the experiment is described in section 3.4 in Materials and

Methods chapter.

4.3.3 Results and Discussion

4.3.3.1 Results

The results reported here are on the effect of coating of calcium carbide grains

with different coating materials on the release of acetylene and ethylene gases and

nitrification inhibition. In the present study independent treatments of coating materials

are included because we have not found any significant change in results regarding plant

growth and yield parameters due to these coating materials compared to control. That is

why calcium carbide with coating materials is used here and in further experimentation.

4.3.3.1.1 Release of acetylene gas from calcium carbide based formulation amended

soil

Data regarding the effect of types of calcium carbide based formulations on the

release of acetylene in soil under laboratory conditions is presented in Fig.4.14a. It is

revealed from the data that acetylene release in soil from all types of calcium carbide

based formulations decreased with time. Maximum acetylene release was noted 3 days

after calcium carbide application in the treatments where calcium carbide was applied in

gelatin capsules or as matrix-III. However, with the passages of time acetylene from both

of these treatments rapidly decreased and only traces were observed at 35th day of

calcium carbide application. Bee wax and paraffin wax coated calcium carbide produced

acetylene in the soil almost in a similar fashion whereas paint coated calcium carbide

performed better and gave a prolong supply of gas than CaC2 coated with both type of

waxes. Out of seven calcium carbide based formulations matrix-I performed the best by

producing more and prolong supply of acetylene in the soil under laboratory conditions.

Matrix-II followed the matrix-I in acetylene release in the soil. At 91st day of calcium

carbide application acetylene concentration of about 4578 and 2435 nmol kg-1 soil were

observed where matrix-I and matrix-II were applied, respectively.

4.3.3.1.2 Release of ethylene gas from calcium carbide based formulation amended

soil

Matrix-I calcium carbide based formulation released a more smooth, consistent

and prolong ethylene supply followed by matrix-II and paint coated calcium carbide

(Fig.4.14b) whereas other calcium carbide formulations produced ethylene in an irregular

fashion. In treatments with encapsulated CaC2 or matrix-III ethylene concentration in the

sample air was increased with time up to 49 days and then started decreasing whereas in

case of other calcium carbide based formulations decreasing trend was observed 63 or 77

days after calcium carbide application. Only trace amount of ethylene was recorded in the

treatments where no calcium carbide was applied. At 91st day after calcium carbide

application, maximum ethylene content (548 nmol kg-1 soil) was observed with matrix-I

(T7) and minimum (9.53 nmol kg-1 soil) in control (T1).

4.3.3.1.3 Acetylene and ethylene flux

Acetylene and ethylene released from the soil treated with different calcium

carbide based formulations were recorded and gaseous flux (ng m-2 min-1) was calculated

and is presented in Fig.4.15. Different calcium carbide based formulations showed

change in acetylene and ethylene flux with time almost directly proportional to acetylene

and ethylene content from different types of calcium carbide based formulations as

presented in Fig. 4.14a and 4.14b, respectively. At 91st day of calcium carbide application

maximum acetylene flux was noted with matrix-I formulation (2.9 ng m-2 min-1) followed

by matrix-II (0.2 ng m-2 min-1) and paint coated calcium carbide (0.04 ng m-2 min-1)

whereas other calcium carbide based formulations showed no acetylene release at that

time. Depending upon the type of calcium carbide based formulation; ethylene flux was

gradually increased for a specific time period and then tended to decrease. At 91st day of

calcium carbide application maximum ethylene flux (0.3 ng m-2 min-1) was noted where

matrix-I formulated calcium carbide was applied and minimum (0.007 ng m-2 min-1) in

control.

4.3.3.1.4 Concentration of ammonium-nitrogen in formulated calcium carbide

amended soil

Maximum nitrification process or oxidation of ammonium was observed in

control (no calcium carbide) treatment and soil ammonium-N was rapidly decreased up to

21 days and almost completely disappeared after 35 days of calcium carbide application

(Fig.4.16a). Calcium carbide application significantly inhibited nitrification process and

ammonium nitrogen stayed for a maximum time in the treatment of matrix-I calcium

carbide formulation. It is revealed from the data that at 91st day after calcium carbide

application maximum concentration of ammonium-N in soil was observed in the

treatment having matrix-I formulation (96 µg g-1 soil) fallowed by matrix-II (67 µg g-1

soil), paint coated CaC2 (45 µg g-1 soil), paraffin wax coated CaC2 (35 µg g-1 soil),

encapsulated CaC2 (32 µg g-1 soil) and matrix-III (12 µg g-1 soil).

4.3.3.1.5 Concentration of nitrate-nitrogen in formulated calcium carbide amended

soil

Application of formulated calcium carbide exhibited a marked effect on

nitrification of ammonium to nitrate. This effect is obvious from the

amount/concentration of nitrate in the calcium carbide treatments. Nitrate-N was ranged

from 9-12 µg g-1 soil in calcium carbide treatments compared to 19 µg g-1 soil in the

control 3 days after calcium carbide application (Fig.4.16b). In control nitrate-N was

rapidly increased with time and reached up to a maximum value (182 µg g-1 soil) at 35th

day of the start of the experiment and then a reduction was noted with time. While in

calcium carbide treatments accumulation of nitrate in soil increased gradually with time

and maximum was observed on 91st day after calcium carbide application. Calcium

carbide in bee wax, paraffin wax or paint coatings also inhibited nitrification process

almost in a similar fashion like that in treatment of matrix-I. However extent of effect

was quite different as is obvious from the nitrate concentration in the respective

treatments. At 91st day of calcium carbide application, minimum nitrate concentration in

soil was observed in the treatment where matrix-I CaC2 based formulation was applied

among all the calcium carbide based formulations.

4.3.3.2 Discussion

Nitrogen use efficiency seldom exceeds 40 % in all types of cropping systems on

the soils of Pakistan. Being a costly input, a small increase in the nitrogen use efficiency

can not only save millions of rupees from fertilizer application but also enhance the crop

yield with minimum impact on environmental pollution. Therefore it is need to develop

certain package of technology to enhance the use efficiency of applied fertilizer by

minimizing losses. Coating of calcium carbide granules is an effort to increase the

nitrogen economy of the soil by controlling the processes involved in transformations of

N in the soil.

Results of the experiment indicate that coating or formulation of calcium carbide

with some inert material effectively slows down the acetylene release. On the basis of

variation in hydrophobic property and coating ability of inert material used, different

calcium carbide based formulations varied in acetylene release in the soil. Matrix-I and

matrix-II CaC2 based formulations performed the best than others due to more stable

nature of polyethylene used in the preparation of these matrices and proper proportion of

calcium carbide with coating material. Better acetylene flux with matrices compared to

wax coated calcium carbide is also reported by Freney et al. (2000).

As ethylene in soil environment is produced as a result of acetylene reduction by

soil microbes so calcium carbide based formulations varied in ethylene production

obviously due to particular or specific nature of formulating material to release acetylene.

Reduction of acetylene released from calcium carbide to ethylene in the presence of

enzyme (nitrogenase) by soil indigenous microorganisms is also reported by Muromtsev

et al. (1988), Muromtsev et al. (1993), Bibik et al. (1995) and Kashif et al. (2007). In all

treatments of calcium carbide, ethylene concentration in the sample air was increased

with time up to 35 or more days and then a reduction trend was observed. This might be

due to the gradual disappearance of acetylene from the soil environment. This point could

be thrashed out to find out biochemical changes occurred in the released ethylene.

More ammonium and less nitrate content in soil treated with calcium carbide over

a longer period of time compared to control indicate that CaC2 based formulations

showed controlled release of acetylene gas in the soil environment which effectively

inhibited nitrification process. Freney et al. (1992a), Keerthisinghe et al. (1993) and Patra

et al. (2006) have already reported inhibition of nitrification due to acetylene released

from calcium carbide.

4.4.1 Experiment 4(A) Effect of Calcium Carbide Based Formulations on Seed Germination, Seedling Growth and Root : Shoot Ratio of Wheat (Laboratory Trial)

4.4.1.1 Introduction Ethylene is the only plant hormone which exists in gaseous form. All higher

plants produce ethylene within plant body at least in trace amounts and it has been

involved in many aspects of plant development processes ranging from germination to

senescence. The effect of ethylene was described for the first time more than hundred

years ago in pea and was then called the classical triple response. The response consists

of swelling of the hypocotyl, growth inhibition in the root and in the hypocotyl and an

exaggerated hook curvature in dark-grown seedlings (Bleecker et al., 1988).

In most plant species, exogenous application of ethylene or ethephon stimulates

the germination of dormant and non dormant seeds, although in some cases they inhibit

or do not affect germination (Ketring, 1977; Esashi, 1991). Ethylene at concentrations

from 0.1 to 200 µl l-1 is usually sufficient to stimulate seed germination of many species.

The inability of plant seeds to germinate under favorable conditions can be related to

primary dormancy which is established during seed development and maturation on

mother plant. Non dormant plant seeds may enter into a state of secondary dormancy

owing to prolong incubation under inadequate conditions for germination. Ethylene or

ethephon not only removes primary dormancy (Kerting and Morgan, 1969; Egley, 1980;

Corbineau and Come, 1992) but also breaks secondary dormancy (Esashi et al., 1978;

Abeles, 1986) in seeds of a number of plant species. Abeles (1986) and Gallardo et al.

(1991) reported that ethylene in addition to other functions also promoted the germination

of non-dormant plant seeds sown under non-optimal conditions.

From the above discussion it becomes clear that plant seeds have some ethylene-

responsive mechanism and their germination inhibition due to dormancy or adverse

conditions can be completely or partially reversed by exogenous ethylene supply

Response of germinating seeds to exogenous ethylene application indicates a deficient

ethylene biosynthesis in the plant body (Nascimento, 1998). Seeds which do not respond

to exogenous ethylene supply may lack responding mechanism or have sufficient

endogenous ethylene biosynthesis with respect to seed germination.

Calcium carbide is a well known precursor of ethylene and due to its fast reaction

with water and rapid release of gas; it has to apply to soil in some suitable formulation

that leads to consistent slow release of gases for a longer periods of time. This experiment

was planned to study the response of wheat to acetylene and ethylene gases released from

calcium carbide based formulations for germination/emergence and other effects on

growth of root and shoot. The experiment was conducted in washed sand culture to

eliminate the nitrification inhibition impact of acetylene on seed germination and root and

shoot growth. This culture was also almost free from mineral nutrients.

4.4.1.2 Materials and Methods Methodology of the experiment is discussed in section 3.4.1 in Materials and

Methods chapter.

4.4.1.3 Results and Discussion Different formulations of calcium carbide (CaC2) was developed by coating

calcium carbide grains with bee wax, paraffin wax, black enamel paint and polyethylene

as described in section 3.4.1 in Materials and Methods chapter. All calcium carbide based

formulations were applied @ 22.5 mg CaC2 kg-1 soil

4.4.1.3.1 Results

4.4.1.3.1.1 Mean emergence time

Data regarding the effect of calcium carbide (CaC2) based formulations on mean

emergence time (days) of wheat seedlings is presented in Fig.4.17a. Except matrix-III, all

other CaC2 formulations significantly decreased the time required for wheat seedling

emergence. Plants emerged out in minimum time (4.08 days) where matrix-I calcium

carbide based formulation was applied (T6). Seed emergence in treatments with matrix-

II, encapsulated or coated CaC2 did not differ from each other and had almost statistically

similar time period for the emergence of seedlings. Maximum time required for seed

emergence was observed in the control treatment where no CaC2 was applied.

4.4.1.3.1.2 Emergence rate index

Emergence rate index (ERI) was used to measure how quickly and uniformly

wheat seedlings emerged in response to application of calcium carbide based different

formulations. A high ERI indicates that seedlings emerged out more quickly and

uniformly whereas a low ERI value indicates a slow and uneven emergence. ERI

numbers are strictly relative and therefore can only be compared within treatments of an

experiment at the same location.

Calcium carbide application significantly increased ERI. Compared to control,

emergence rate index was increased by 16, 45 and 24 % due to calcium carbide applied in

capsules, matrix-I and matrix-II formulations, respectively. Maximum ERI was noted

where calcium carbide was applied as matrix-I and in bee wax coating. Most of the

coatings such as encapsulation, paraffin wax, paint and matrix-II showed statistically

similar values of emergence rate index (Fig.4.17b).

4.4.1.3.1.3 Fresh biomass weight

Data regarding fresh biomass weight per plant (FBW) of wheat at 3, 6, 12 and 15

days after sowing is presented in Fig.4.18. Calcium carbide application increased FBW in

the treatment where it was applied in formulation matrix-I (T6), matrix-II (T7) and in

paint coating (T5) compared to control. Whereas FBW in the treatments other than these

formulations did not differ significantly from control when observed at day 3 after

sowing. Response of wheat seedlings to different calcium carbide based formulations 3

days after sowing is elaborated in the form of photograph in Fig.4.19.

After 6 days of sowing, maximum FBW (157.8 mg plant-1) was noted in the

treatment of matrix-I (T6). It was followed by matrix-II (T7) and paint coated calcium

carbide (T5). Almost similar values for FBW were noted in treatments of encapsulated

(T2), bee wax (T3) and paraffin wax coated calcium carbide (T4) however these values

are significantly higher than control. FBW obtained in the treatment of matrix-III (T8)

formulation did not differ significantly from control.

At 15th day of sowing, wheat pants were somewhat withered due to the lack of

nutrients in the sand medium, even than effect of calcium carbide application on fresh

biomass weight of wheat became more prominent at 12th and 15th day of sowing than

previous fresh biomass-determination times. Maximum FBW was observed in the

treatments of matrix-I (T6) and matrix-II (T7) formulations, followed by treatments with

paint (T5), bee wax (T3) and paraffin wax coated calcium carbide (T4). Matrix-III (T8)

and encapsulated CaC2 (T2) produced almost similar but comparatively more FBW than

control (T1).

4.4.1.3.1.4 Root and shoot length

Data regarding effect of calcium carbide based formulations on root and shoot

length (cm) of wheat seedlings is presented in Fig.4.20a. Data revealed that all CaC2

based formulations except matrix-III, significantly increased root length after 15 days of

sowing compared to control. Maximum root length was noted in the treatment with

matrix-I (Fig.4.21) followed by bee wax coated, paint coated and matrix-II CaC2.

Encapsulated and paraffin wax coated calcium carbide influenced root length in a similar

way. Unlike to root length, shoot length was not much affected by calcium carbide based

application after 15 days of sowing. This pointed out that calcium carbide stimulates root

growth first and then other plant parts.

4.4.1.3.1.5 Root and shoot weight

Effect of calcium carbide application on root and shoot weight (mg plant-1) of

wheat seedlings was observed 15 days after sowing (Fig.4.20b). Response of root growth

to CaC2 application was more prominent compared to that of shoot. Root weight was

significantly increased by the application of CaC2 whereas increase in shoot weight was

statistically insignificant. Maximum root weight was recorded where matrix-I and matrix-

II formulations were applied and it was followed by paint coated calcium carbide.

Statistically similar root weight was observed in the treatments of encapsulated, bee wax

and paraffin wax coated calcium carbide. Moreover, root weight in the treatment of

matrix-III did not differ from that of control.

4.4.1.3.1.6 Root:shoot ratios

Root:shoot ratios by length and weight of wheat observed 15 days after sowing

are presented in Fig.4.22. Though increase in root:shoot ratio by weight was observed in

response to CaC2 application but it was not significant compared to control. However,

application of calcium carbide based formulations significantly increased root:shoot ratio

by length. Maximum root:shoot ratio by length was observed where calcium carbide was

applied as matrix-I (1.29), followed by paint coating (1.14) and matrix-II (1.09) while it

was minimum in control (0.75). Other calcium carbide formulations show statistically

similar influence on root:shoot ratio by length.

4.4.1.4.2 Discussion

Calcium carbide (CaC2) is now recognized as a well known precursor of ethylene

(Muromtsev et al., 1988; Muromtsev et al., 1993; Bibik et al., 1995; Kashif et al., 2008).

Effect of ethylene released from CaC2 on root and shoot growth was studied in this

experiment. Time taken for wheat seed germination and seedling emergence was reduced

in response to calcium carbide application probably due to ethylene gas released from

calcium carbide. It was already reported by Abeles (1986) that ethylene stimulates the

germination of plant seeds by promoting the embryonic hypocotyl cell expansion instead

of acting on the enveloping tissues. Later on Dutta and Bradford (1994) postulated that at

higher temperature, 1-aminocyclopropane-1-carboxylic acid (ACC), an ethylene

precursor, extends the upper temperature limit for germination of seeds by lowering the

seed water potential and promote the initiation of growth.

Involvement of exogenous ethylene in seed germination is a widely accepted fact

(Abeles and Lonski, 1969; Burdett, 1972a; Negm et al., 1972; Keys et al., 1975; Rao et

al., 1975; Dunlap and Morgan, 1977; Abeles, 1986; Khan and Prusinski, 1989; Huang

and Khan, 1992, Nascimento, 1998; Nascimento et al., 1999a, 1999b), but the

mechanistic details are poorly understood. However, some possibilities of ethylene

involvement in seed germination are a) by interaction with endogenous hormones (e.g.

Abscisic acid ); b) by interaction with growth promoters required to maximize a given

physiology response; c) by interaction in physiological response not specific for a single

growth promoter; and d) by affecting enzyme synthesis and secretion (Ketring, 1977).

Ketring and Morgan (1970) reported that abscisic acid (ABA) reduces the

production of ethylene in peanut seeds. In another case, ABA not only inhibits ethylene

production but also reduced the germination of chickpea seeds (Gallardo et al., 1991). It

was also reported that exogenous supply of ethylene overcomes the inhibitory effects of

ABA on germination of dormant peanut seeds (Ketring and Morgan, 1970). The release

of dormancy in lettuce seeds by ethylene, however, was not a result of decreasing ABA-

like compounds (Rao et al., 1975), since that ethrel (ethylene releasing compound)

induced germination during seed imbibition was impaired in the presence of ABA. In

recent studies using ethylene responsive mutants of Arabidopsis sp., endogenous ethylene

promoted seed germination by decreasing sensitivity to endogenous ABA (Beaudoin et

al., 2002). Other mutants, defective in their response to ethylene, also showed altered

ABA synthesis. Thus ethylene appears to be a negative regulator of ABA during

germination (Ghassemian et al., 2002).

Burdett and Vidaver (1971) found that both ethylene and gibberellin were

necessary to stimulate germination of lettuce at high temperature. For example, ethylene

promoted germination of lettuce in the dark only in the presence of gibberellin (Dunlap

and Morgan, 1977). Gibberellin slightly stimulates ethylene production in peanut seeds at

28°C (Ketring and Morgan, 1970). The action of gibberellin in lettuce seed germination

might be through promotion of ethylene synthesis, which might then stimulate

germination by other mechanism (Stewart and Freebairn, 1969).

Ethylene also stimulates the separation of cells because it is involved in the

activation of cell wall degrading enzymes, such as endo-β-1,4-glucanases, has been

studied in fruit softening (Casadoro et al., 1999). Other cell wall degrading enzymes,

such as endopolygalacturonase, some isoforms of α-galactosidase, β-arabinosidase, and

galactanase, appear to have ethylene-dependency (Pech et al., 1999). Keeping in view the

interaction of ethylene with enzyme activity, it looks possible that ethylene enhances seed

germination and seedling emergence by activating cell wall enzymes responsible for

endosperm digestion.

Ethylene produced from calcium carbide application significantly enhanced

root:shoot ratio by length and its effect on root:shoot ratio by weight was not significant.

This indicates that calcium carbide application improved root proliferation on the cast of

same photosynthates when checked 15 days after sowing. Grodzinski and Woodrow

(1989) reported a similar shift in the root:shoot ratio in ethephon treated tomatoes. They

suggested that this shift in carbon partitioning may be caused by a reduction in the

dominant carbon sinks. Root growth improvement with ethylene is also reported by

Abeles (1992), Sharma and Yadav (1996), Freney et al. (2000) and Mahmood et al.

(2002).

The findings of experiment 3 further elaborated the results of this experiment that

all seven calcium carbide based formulations, applied at the same rate, varied in ethylene

production, flux and smoothness with which it is evolved. That is why germinating wheat

seeds respond in a different way to various calcium carbide formulations.

4.4.2 Experiment 4(B) Effect of Different Doses of Matrix-I Based Calcium Carbide on Wheat Seedling Emergence (Pot Trial)

4.4.2.1 Introduction Results of experiment 4(A) revealed that matrix-I calcium carbide formulation (21

% calcium carbide, 58 % polyethylene and 21 % plaster of paris) performed

comparatively the best in reducing mean emergence time and increasing fresh biomass

weight of wheat seedlings. It was then planned to check the effect of different rates of

application of calcium carbide based matrix-I formulation on wheat seedling emergence.

The objective of this experiment was to find out the best rate of application of matrix-I in

terms of its effect on wheat seed germination and seedling emergence.

4.4.2.2 Materials and Methods Methodology of the experiment is discussed in section 3.4.2 in Materials and

Methods chapter.

4.4.2.3 Results and Discussion

4.4.2.3.1 Results

4.4.2.3.1.1 Mean emergence time

Data regarding effect of different rates of matrix-I formulation on mean

emergence time (MET) of wheat seedlings is summarized in Fig.4.23a. It is obvious from

the data that application of CaC2 based matrix-I significantly reduced MET. Wheat

seedlings were emerged in minimum time (32 % less than that of control) where calcium

carbide based formulation matrix-I was applied @ 15 mg CaC2 kg-1 soil. Emergence of

wheat seedlings was at 5.28, 4.63, 4.00 and 4.30 days in control, 7.5, 15 and 22.5 mg

CaC2 kg-1 soil, respectively. Estimated values calculated from the comparison of mean

emergence time at various calcium carbide levels indicate that seedling emergence time

was shortened to 7.5 % at treatment of 15 mg CaC2 kg-1 soil than 22.5 mg CaC2 kg-1 soil.

4.4.2.3.1.2 Emergence rate index

Emergence rate index (ERI) was also markedly influenced by the different doses

of calcium carbide (Fig.4.23b). Maximum ERI was observed in the treatment where

calcium carbide based formulation matrix-I was applied @ 15 mg CaC2 kg-1 soil. Mean

ERI observed in different treatments can be arranged in descending order as 15 > 22.5 >

7.5 > 0 mg CaC2 kg-1 soil.

4.4.2.3.2 Discussion

Results are evident that application of different rates of matrix-I calcium carbide

based formulation significantly affected the mean emergence time and emergence rate

index of wheat seedlings compared to control. Decrease in MET and increase in ERI due

to matrix-I calcium carbide based formulation application is owing to the ethylene

released from calcium carbide. Role of ethylene as a plant growth regulator in stimulation

of seed germination of dormant and non-dormant seeds have already been reported by

Ketring (1977) and a number of other researchers (Abeles, 1992; Sharma and Yadav,

1996; Freney et al., 2000; Mahmood et al., 2002). As application of calcium carbide in

appropriate dose could be able to release right amount of ethylene in the soil that is why

application of different rates of calcium carbide affected seed germination and emergence

in a different fashion. Application of matrix-I formulation @ 15 mg CaC2 kg-1 soil was

found the best and appropriate rate of application regarding seedling emergence. Seedling

emergence was delayed in the treatment where matrix-I was applied @ 22.5 mg CaC2 kg-

1 soil compared to that of 15 mg kg-1 soil. This might be due to release of high amount of

ethylene in proximity of seeds that instead of stimulating inhibited seed germination for

very short period. Germination inhibition with comparatively higher rates of calcium

carbide is also reported by Kashif et al. (2008).

The results of this experiment provide information that application of calcium

carbide at right rate could be useful for early germination and seedling emergence.

Moreover, this information could be particularly useful for vegetable growers where they

need early and fast growth of vegetables to fetch more benefit from the market.

4.5 Experiment 5 Effect of Calcium Carbide Based Formulations on Growth, Yield and Nitrogen Uptake of Wheat (Pot Trial)

4.5.1 Introduction Calcium carbide as a nitrification inhibitor is studied by a number of workers

(Aulakh et al., 2001; Randall et al., 2001; Yaseen et al., 2006; Kashif et al., 2008). Due

to its rapid reaction with water it is mostly applied to soil in some encapsulation form so

that a sustained supply of acetylene gas may be produced to inhibit the activity of

ammonium oxidizing enzyme for a longer period. Mostly waxes are used for the

encapsulation of calcium carbide. Although they served the purpose well but under high

temperature conditions like in Pakistan and large scale soil application made this type of

formulation ineffective or impractical. Freney et al. (2000) suggested a new way to

encapsulate calcium carbide. They blended calcium carbide with molten polyethylene

and calcium carbonate mixture with different ratios and named the materials as matrices.

They noted that matrices performed much well than wax coated CaC2 in producing

persistent supply of acetylene gas to inhibit nitrification.

Soil microbes having nitrogenase activity have the ability to reduce acetylene

released from calcium carbide to ethylene. Ethylene is a phyto hormone and plays roles

in physiological processes throughout the life cycle of the plant (Mattoo and Suttle,

1991). Ethylene has been implicated in developmental processes such as the formation of

apical hook in dark-grown seedlings, regulation of cell expansion and flower

development. In case of cereals ethylene has been reported to reduce lodging and enhance

grain yield (Dahnous et al., 1982; Harms, 1986; Simmons, et al., 1988; Boutaraa, 1991).

. In this study calcium carbide was formulated/encapsulated with different types of

materials and response of wheat to these CaC2 formulations was tested in a pot trial with

an aim to select a better formulation with respect to growth, yield and N uptake of wheat

crop grown in a field soil growth medium.

4.5.2 Materials and Methods Methodology of the experiment is discussed in section 3.5 in Materials and

Methods chapter.

4.5.3 Results and Discussion

4.5.3.1 Results

4.5.3.1.1 Plant height

Data regarding the effect of calcium carbide based formulations on plant height

(cm) of wheat is presented in Fig.5.1. Minimum plant height (69.30 cm) was observed in

T1 (control) and maximum (81.83 cm) in the treatment (T2) of NPK fertilizers alone.

Plant height was reduced where calcium carbide was applied in either formulation along

with NPK fertilizer compared to that of NPK fertilizer alone. A significant reduction in

plant height was noted with matrix-I (T7) and matrix-II (T8) CaC2 based formulations

compared to that of NPK fertilizers alone. Whereas other calcium carbide based

formulations did not differ from each other in their influence on plant height however

these reduced plant height compared to that of NPK fertilizer alone treatment.

4.5.3.1.2 Number of tillers

Different calcium carbide based formulations, when applied @ 22.5 mg kg-1 soil

with recommended dose of NPK fertilizers (60-45-30 mg kg-1 soil), increased total as

well as fertile number of tillers pot-1 of wheat (Fig.5.2). Minimum number of total (15.7)

and fertile (10.3) tillers pot-1 were noted in control (T1) whereas tillering were maximum

(total = 32.3 and fertile = 27.0) when calcium carbide was applied in matrix-I formulation

with recommended NPK fertilizers (T7). Treatments with paint coated calcium carbide

(T6), matrix-I (T7) and matrix-II (T8) were statistically at par in producing fertile tillers.

Statistically similar number of spike bearing tillers was observed with calcium carbide

application in matrix-III (T9), bee wax (T4) or paraffin wax (T5) coated formulations.

Tillers were also significantly increased with alone nitrogen fertilizer application (T2)

compared to control (T1).

4.5.3.1.3 Root weight

Root weight of wheat was significantly increased in the treatments of calcium

carbide plus NPK fertilizers compared to the treatment without calcium carbide (Fig.5.3).

Maximum root weight (11.62 g pot-1) was noted in T7 (matrix-I) and minimum (6.68 g

pot-1) in T1 (control, no N fertilizer). Root weight in treatment T8 (matrix-II) was

statistically similar to that of T6 (paint coated CaC2). Encapsulated, bee wax or paraffin

wax coated calcium carbide treatments had statistically similar effect on root growth.

Root weight in the treatment of matrix-III (T9) was statistically at par to that where alone

NPK fertilizers were applied.

4.5.3.1.4 Thousand grains weight

Effect of calcium carbide based formulations on 1000-grains weight (g) of wheat

is shown in Fig.5.4. Calcium carbide significantly increased 1000-grains weight of wheat

when CaC2 was applied @ 22.5 mg kg-1 in coatings, matrix-I or matrix-II formulations.

Thousand grains weight in treatments of matrix-III and encapsulated calcium carbide did

not differ too much from that of fertilizer alone treatment. Minimum thousand grains

weight (41.8 g) was observed in treatment where no N fertilizer was applied (T1) i.e.

control and maximum (49.4 g) where matrix-I calcium carbide based formulation was

applied in combination with recommended rate of NPK fertilizers. Statistically similar

1000-grains weight was noted in treatments where matrix-I, matrix-II, bee wax, paraffin

wax and paint coated calcium carbide was applied.

4.5.3.1.5 Biological yield

Data regarding effect of calcium carbide formulations on biological yield of

wheat is presented in Fig.5.5a. Nitrogen fertilizer application significantly increased

biological yield of wheat compared to control and it was further improved with the

application of formulated calcium carbide along with NPK fertilizers. Maximum

biological yield of wheat (70.9 g pot-1) was observed in T7 (matrix-I) and it was followed

by T8 (matrix-II) and T6 (paint coated). Statistically similar biological yield was

observed with the application of gelatin encapsulated, bee wax and paraffin wax coated

calcium carbide formulations. Biological yield in the treatment T9 (matrix-III) was

statistically at par with that produced in the treatment T3 (encapsulated CaC2).

4.5.3.1.6 Grain yield

Data regarding effect of calcium carbide based formulations on grain yield (g pot-

1) of wheat is presented in Fig.5.5b. Calcium carbide application in different formulations

significantly enhanced grain yield of wheat over fertilizer alone. Maximum grain yield

(31.9 g pot-1) was observed where matrix-I (T7) calcium carbide based formulation was

applied with recommended dose of NPK fertilizers compared to that of NPK fertilizers

alone. Grain yield in the treatment T7 was followed by treatments where matrix-II (T8)

and paint coated calcium carbide (T6) were applied. Grain yield was statistically similar

in the treatments of bee wax and paraffin wax coated calcium carbide based formulations.

4.5.3.1.7 Nitrogen concentration in different plant parts of wheat

Effect of calcium carbide based formulations on nitrogen (N) concentration (%) in

wheat roots, straw and grain is presented in Fig.5.6a, Fig.5.6b and Fig.5.6c, respectively.

Nitrogen concentration in all three plant parts increased with nitrogen fertilizer

application and it was further enhanced where calcium carbide was applied with NPK

fertilizers. Maximum N concentration in wheat root, straw and grain were observed

where matrix-I formulated calcium carbide was applied in combination with NPK

fertilizers. Encapsulated, bee wax coated, paraffin wax coated and matrix-III calcium

carbide based formulations had statistically similar influence on N concentration in wheat

root. Matrix-I, matrix-II and paint coated calcium carbide formulations significantly

improved root N concentration whereas other formulations were at par compared to NPK

fertilizer alone treatment regarding N concentration in root.

Concentration of (N) in straw was maximum (0.60 %) with matrix-I, which was

statistically at par with matrix-II and paint coated calcium carbide treatments. Bee wax

and paraffin wax coated CaC2 based formulations were statistically similar in their

influence on straw N concentration. Encapsulated and matrix-III treatments did not differ

significantly from that of NPK alone treatment regarding N concentration in wheat straw.

Maximum (N) concentration in wheat grain was observed in treatments where

matrix-I, matrix-II, paint coated or paraffin wax coated calcium carbide was applied.

Encapsulated and matrix-III calcium carbide based formulations did not differ

significantly from that of alone fertilizers treatment.

4.5.3.1.8 Nitrogen uptake by different plant parts of wheat

The effect of calcium carbide based formulations on nitrogen uptake (mg kg-1) by

wheat root, straw and grain is presented in Fig.5.7a, Fig.5.7b and Fig.5.7c, respectively.

All three plant parts accumulated more N in the treatments where calcium carbide was

applied in either formulation compared to that of with N fertilizer alone. Wheat root,

straw and grain took up minimum N in control (no N fertilizer) and maximum where

calcium carbide was applied as matrix-I, followed by matrix-II and in paint coating with

recommended dose of N fertilizer. Statistically similar N uptake was observed in wheat

root and straw where encapsulated, bee wax and paraffin wax coated calcium carbide

were applied with recommended dose of N fertilizer. In treatments of bee wax coated

calcium carbide wheat grains took up statistically similar N compared to that of with

paraffin wax coated CaC2 application. Moreover, matrix-III and encapsulated calcium

carbide had almost similar effect on N uptake by grain.

It was observed that maximum N was accumulated in grains followed by straw

and roots. It was also noted that relative N partitioning in different plant parts of wheat

was more or less altered with the application of calcium carbide in different formulations

when compared among themselves and with fertilizer as well as control (Fig.5.9).

4.5.3.1.9 Soil mineral nitrogen content

Data in Fig.5.10 present the effect of calcium carbide based formulations on soil

mineral nitrogen (nitrate-N and ammonium-N) content determined 8 weeks after CaC2

application. Total mineral nitrogen content was significantly increased with N fertilizer

application. More ammonium-N and less nitrate-N concentrations were observed in the

calcium carbide treatments however, reverse response was observed in plots treated with

NPK fertilizers alone. Maximum NH4+-N and minimum NO3

--N concentrations were

observed in the order of matrix-I fallowed by matrix-II, paint coated, paraffin wax coated,

bee wax coated, matrix-III and gelatin encapsulated calcium carbide based formulations.

4.5.3.2 Discussion

Varying response of wheat in terms of growth and yield parameters to different

calcium carbide based formulations applied at the same rate is owing to the specific

acetylene flux and ethylene production from each formulation. Matrix-I and matrix-II

formulations performed better as these were seemed to produce prolonged and sustained

supply of acetylene and ethylene gases in the soil environment. Ethylene released from

calcium carbide reduced plant height of wheat and improved number of spike bearing

tillers and ultimately resulted in increase in grain yield. Inrease in grain yield with

ethephon (an ethylene releasing compound) application in the absence of lodging has

been attributed to increased spikes per area (Bahry, 1988, Hill et al., 1982) or spikes per

plant (Ramos et al., 1989). Increase in root weight with calcium carbide application is a

typical response of plant to ethylene (Sharma and Yadav, 1996; Freney et al., 2000; and

Mahmood et al., 2002). This enhanced root growth could help to fetch more nutrients

from the soil and thus contribute to yield increase.

Grain yield of wheat depends upon the parameters which directly or indirectly

contribute to it. Increase in grain yield may be due to the increase in number of spikes per

plant, better root growth which in turn uptake more nutrients for healthy grain formation,

prolong nitrogen supply due to nitrification inhibition and mixed nitrogen nutrition

instead of nitrate alone. This all happened most probably due to addition of calcium

carbide in the soil environment.

Presence of more ammonium and less nitrate in calcium carbide treated soil than

that of NPK alone treatment indicates that acetylene released from calcium carbide

significantly inhibited nitrification process. Other researchers (Freney et al., 2000;

Aulakh et al., 2001; Randall et al., 2001; Patra et al., 2006) also reported that slow

release of acetylene (C2H2) from encapsulated calcium carbide (ECC) reduced ammonia

mono-oxygenase by reducing the population of ammonia oxidizing bacteria and has the

potential to retard the enzyme activities in favor of C and N conservations in a semi-arid

agro-ecosystem. Similarly Freney et al. (1992a) reported that addition of ECC with the

nitrogen fertilizer blocked nitrification in irrigated wheat for more than 10 weeks, thus

preventing denitrification loss of nitrogen. In addition, loss of applied nitrogen from

flooded rice in the Murrumbidgee Irrigation Area was reduced from 56% to 13% and

methane production was also markedly reduced (Keerthisinghe et al., 1993).

All this discussion suggest the positive effect of calcium carbide application on

growth and yield of wheat because of yield increase due to efficient use of nutrients.

These results suggest recommending use of calcium carbide in combination with N

fertilizer to improve wheat and other cereals yield per unit area.

4.6 Experiment 6 Effect of Rate and Application Depth of Matrix-I Calcium Carbide Based Formulation on Growth Yield and Nitrogen Uptake of Wheat (Pot Trial)

4.6.1 Introduction Calcium carbide being a potent source of nitrification inhibitor gas acetylene and

plant hormone ethylene (Muromtsev et al., 1988; Arshad and Frankenberger, 2002). Both

the gases had pronounced influence on plant growth from germination to maturity and

thus influence the yield and yield contributing parameters (Bronson et al., 1992; Freney

et al., 1992a; Ahmad et al., 2004; Yaseen et al., 2005, 2006; Kashif et al., 2008).

Since acetylene inhibits the ammonium oxidizing enzyme in the soil and its

conversion to ethylene also depends upon soil microbes therefore, variation in application

depth of calcium carbide will change the volume of soil exposed to acetylene supply and

may thus influence the nitrification inhibition and ethylene production from calcium

carbide. Secondly, root exposure to ethylene supply may also change with changing the

application depth of CaC2 and thus in turn its influence on plant growth and development

may change. Entrapment of gases in the soil due to increasing depth of calcium carbide is

also a possible way that can change crop responses to calcium carbide application.

Matrix-I is the calcium carbide formulation which performed the best in the

previous experiments to improve seedling emergence, growth and yield of wheat crop. In

this experiment response of wheat to different doses of calcium carbide based

formulation matrix-I applied at different soil depths was evaluated to find out the best

rate and depth of application of calcium carbide.

4.6.2 Materials and Methods Methodology of the experiment is described in section 3.6 in Materials and

Methods chapter.

4.6.3 Results and Discussion Since application of calcium carbide @ 22.5 mg kg-1 soil was found the best of

calcium carbide in the form of matrix-I formulation in the previous experiment

(experiment 5). Now its depth of application was evaluated by lowering and increasing

the rate of CaC2 application from 15 mg kg-1 soil. Results obtained regarding different

growth and yield parameters and N uptake of wheat in response to calcium carbide are

explained in the following pages.

4.6.3.1 Results

4.6.3.1.1 Plant height

Data regarding effect of rate and application depth of calcium carbide in the form

of matrix-I formulation on plant height (cm) of wheat is presented in Table 6.1. A

significant reduction in plant height was noted with increasing rate and application depth

of calcium carbide. Maximum plant height was observed in the treatments with no

calcium carbide (control) or where it was applied at soil surface. Plant height was

statistically similar and minimum in treatments where matrix-I was applied @ 15 and

22.5 mg CaC2 kg-1 soil at 8 and 12 cm depth.

4.6.3.1.2 Number of tillers

Rate and application depth of calcium carbide (matrix-I) affected number of total,

fertile and unfertile tillers of wheat as is presented in Table 6.2, 6.3 and 6.4, respectively.

Total number of tillers was significantly increased with increasing rate and application

depth of calcium carbide and maximum number of tillers was observed in the treatment

where calcium carbide was applied @ 22.5 mg kg-1 soil at 12 cm depth with NPK

fertilizers.

Statistically similar number of fertile tillers was observed in treatments where

calcium carbide was applied @ 7.5 mg kg-1 soil at 12 cm, 15 mg kg-1 soil at 4 cm or 8 cm

and 22.5 mg kg-1 soil at 4 cm soil depth. Total as well as fertile number of tillers did not

differ in treatment where CaC2 was applied at soil surface compared to control having

NPK fertilizers alone. Maximum number of fertile tillers was obtained in the treatment of

matrix-I @ 15 mg CaC2 kg-1 soil applied at 8 cm depth..

As compared to other treatments more number of unfertile tillers was produced in

treatments where CaC2 @ 15 mg kg-1 soil at 12 cm and 22.5 mg kg-1 soil at 8 or 12 cm

depth was applied.

4.6.3.1.3 Thousand grains weight

Calcium carbide (matrix-I) application significantly increased thousand grains

weight (g) of wheat (Table 6.5). Maximum 1000-grains weight (48.8 g) was observed

where calcium carbide was applied @ 15 mg kg-1 soil at 8 cm depth. Whereas CaC2 @

7.5 mg kg-1 soil at 12 cm depth and 15 or 22.5 mg kg-1 soil at 4 cm depth were

statistically at par with the treatment where maximum 1000-grains weight was observed.

Calcium carbide application @ 22.5 mg kg-1 soil at 12 cm depth showed a reduction in

1000-grains weight compared with its lower rates at shallower depths. Treatments where

calcium carbide applied at soil surface did not influence 1000-grains weight in

comparison with fertilizer alone.

4.6.3.1.4 Biological yield

Data regarding effect of rate and application depth of calcium carbide on

biological yield (g pot-1) of wheat is presented in Table 6.6. It was noted that CaC2

application significantly enhanced biological yield and maximum biological yield was

observed where calcium carbide was applied @ 15 or 22.5 mg kg-1 soil at 8 cm depth

followed by 22.5 mg kg-1 soil at 4 cm depth. A reduction in biological yield of wheat was

observed where calcium carbide was applied at depth greater than 8 cm compared to that

where it was applied at 8 cm depth. Biological yield was not affected where calcium

carbide was applied at the soil surface.

4.6.3.1.5 Grain yield

Effect of rate and application depth of calcium carbide (matrix-I) on grain yield (g

pot-1) of wheat is presented in Table 6.7. It is revealed from the data that calcium carbide

significantly improved grain yield of wheat when applied with NPK fertilizers. Grain

yield was increased with increasing rate and application depth of calcium carbide up to

15 mg kg-1 soil and 8 cm depth whereas at higher rate and greater depth, a reduction trend

in grain yield was noted. Maximum grain yield was observed in treatment where CaC2

@ 15 mg kg-1 soil was applied at 8 cm depth. It was followed by 22.5 mg kg-1 soil

application at 8 or 4 cm and 7.5 mg kg-1 soil application at 12 cm depth. Grain yield in

the treatment where calcium carbide was applied at soil surface did not differ from that of

NPK alone.

4.6.3.1.6 Nitrogen concentration in wheat straw and grains

Nitrogen concentration (%) in wheat straw (Table 6.8) and grains (Table 6.9)

significantly increased with increasing rate and application depth of calcium carbide.

Maximum N concentration in straw was observed where calcium carbide was applied @

7.5 mg kg-1 soil at 12 cm, 15 mg kg-1 soil at 8 or 12 cm and 22.5 mg kg-1 soil at 4, 8 or 12

cm depth.

In case of grain, maximum N concentration was noted where CaC2 was applied @

22.5 mg kg-1 soil at 8 cm depth. Nitrogen concentration in treatments with calcium

carbide @ 15 and 22.5 mg kg-1 soil at 12 cm depth were statistically at par with each

other. Comparison between treatments of fertilizer alone and calcium carbide applied at

soil surface showed non-significant effect on nitrogen concentration in wheat straw and

grain.

4.6.3.1.7 Nitrogen uptake by wheat straw and grains

Data regarding effect of rate and application depth of calcium carbide (matrix-I)

on nitrogen uptake (g pot-1) of wheat straw and grains is summarized in Table 6.10 and

Table 6.11, respectively. Nitrogen uptake in straw and grain increased significantly in the

treatments where NPK fertilizers were applied in combination with CaC2 compared to

NPK fertilizer alone. In both plant parts, maximum nitrogen uptake was observed where

calcium carbide @ 15 or 22.5 mg kg-1 soil was applied 8 cm deep followed by the

treatments where it was added @ 22.5 mg kg-1 soil at 4 cm depth. A reduction in N

uptake was noted where calcium carbide was added 12 cm deep compared with the

treatment where it was applied at 8 cm depth. Compared to NPK alone, surface

application of calcium carbide did not show any significant influence on N uptake.

4.6.3.2 Discussion

Results of this study indicate that application of CaC2 at right rate and proper soil

depth with recommended dose of NPK fertilizers significantly increased grain yield of

wheat. It reduced the plant height due to stimulatory effect of ethylene on early root

growth. Such responses of plant due to application of ethephon (ethylene releasing liquid

compound) on plant root growth and development have already been reported by Cooke

et al. (1983). Healthy root growth actively explores more volume of soil and absorbs

more nutrients from the soil to enhance tillering. Many workers have reported that

production of acetylene/ethylene in rhizosphere stimulates the tillering (Freney et al.,

1990; Sharma and Yadav, 1996; Randall et al., 2001; Ahmad et al., 2004).

Increase in grain yield of wheat with the application of CaC2 is attributed to

enhanced uptake of nutrients by wheat roots. It may be due to increase in root primordia

to explore more volume of soil to acquire nutrients (Ahmad et al., 2004). Enhanced N

uptake by grains in response to CaC2 application may be due to nitrification inhibitory

effect of acetylene released from applied CaC2. Inhibition of nitrification process for

certain periods helps to maintain applied fertilizer N in plant available form over

extended periods of time. Interaction between rate and application depth of calcium

carbide revealed that lower rates of calcium carbide at greater depths benefited the crop

production in the similar way as higher rates applied at shallower depths. It is because of

the fact that ethylene released from calcium carbide enters the plant body via roots.

Increase in application depth of CaC2 not only allows acetylene to penetrate into greater

volume of soil to inhibit nitrification but also increase the root surface area by stimulating

root growth for the absorption of nutrients. This activity can improve N economy of soil

for greater period and side by side also improve N use efficiency by crop.

Production of more number of unfertile tillers with calcium carbide, applied @

22.5 mg kg-1 soil at 12 cm depth might be due to the production of excess ethylene in the

rhizosphere. Decrease in number of spike bearing tillers per unit area due to excess

ethylene accumulation in the soil was also reported by Klassen and Bugbee (2002). The

results obtained, therefore, suggest that application of calcium carbide at right rate and

proper depth could improve growth and yield contributing parameters for improving

wheat grain yield. It can be concluded from the above results that application of CaC2 @

15 mg kg-1 soil at 8 cm depth gave better results regarding all growth and yield

parameters of wheat. Therefore, it can be test further with changing nitrogen fertilizer

application rate. This is necessary to improve nitrogen use efficiency by judicious use of

N fertilizer.

4.7 Experiment 7 Response of Wheat to Soil Applied Matrix-I Formulated Calcium Carbide with and without Nitrogen Fertilizer (Pot Trial)

4.7.1 Introduction Nitrogen (N) fertilizer, when applied through broadcast over the soil

surface, most of it lost due to ammonia volatilization (Freney et al., 1992a,

1992b). These losses can be checked by applying N fertilizer through

incorporation or deep placement methods. However, close contact of drilled

fertilizer with soil increases the processes of nitrification/denitrification and N

loss in the form of N2O emissions and/or nitrate leaching (Freney et al., 1993). It

is thus crucial to incorporate or deep place N fertilizer with some nitrification

inhibitor to enhance nitrogen use efficiency and yield of crop.

Previous studies have shown that encapsulated calcium carbide (ECC)

when applied to soil creates a low level of acetylene, which is adequate to inhibit

nitrification (Berg et al., 1982; Bronson et al., 1992). Keerthisinghe et al. (1996)

reported that addition of ECC to soil significantly reduced the emission of N2 +

N2O from incorporated and deep placed urea and resulted in increased

exchangeable ammonium concentration and thus a prolonged stay of fertilizer N

in the soil may benefit more crop production.

Calcium carbide is also a famous precursor of ethylene. Acetylene

released from ECC is reduced to ethylene by soil microorganisms, which enters

the plant through roots (Muromtsev et al., 1988; Bibik et al., 1995). Ethylene is a

plant hormone which is involved in almost all developmental processes ranging

from germination of seed to senescence of various organs and in many responses

to environmental stress (Lurssen, 1991). There is a cross talk between the

ethylene signaling pathway and other hormone signaling pathways, particularly

with auxin, whose effects are often mediated by ethylene. The wide range effects

of ethylene have made it a topic of intense research for decades and a lot of work

has been done on different crops regarding ethylene effects.

In the previous studies Matrix-I calcium carbide based formulation

performed as the most sustainable source of acetylene/ethylene and the best

nitrification inhibitor than other formulations tested. Present study was planned

to check the response of growth and yield parameters and nitrogen use efficiency

of wheat plants at different rates of matrix-I formulated calcium carbide in the

presence of different levels of nitrogen.

4.7.2 Materials and Methods

Methodology of this experiment is described in section 3.7 of Materials

and Methods chapter

4.7.3 Results and Discussion

4.7.3.1 Results

4.7.3.1.1 Plant height

Effect of rate of calcium carbide (matrix-I) with and without different doses of N

fertilizer on plant height (cm) of wheat is shown in Fig.7.1. Plant height was significantly

increased with increasing rate of N fertilizer whereas calcium carbide application reduced

plant height compared to that in the treatment of N fertilizer alone. Minimum plant height

(73.9 cm) was noted where calcium carbide was applied @ 22.5 mg kg-1 soil with no N

fertilizer while it was maximum (94.3 cm) in treatment where full recommended dose of

N fertilizer was applied without calcium carbide. Comparison of all the three N fertilizer

levels indicates that CaC2 application @ 7.5 and 15 mg kg-1 soil had statistically similar

effect on plant height in the presence of N fertilizer while higher dose of CaC2 (22.5 mg

kg-1 soil) showed significant effect on plant height.

4.7.3.1.2 Number of tillers

Data on the effect of rate of calcium carbide (matrix-I) with and without N

fertilizer on total and fertile number of tillers pot-1 of wheat is presented in Fig.7.2 and

Fig.7.3, respectively. Number of tillers as well as number of spikes bearing tillers (fertile

tillers) per pot was increased with increasing rate of nitrogen fertilizer. These were

further increased with the addition of calcium carbide to the N fertilized pots. It is quite

obvious from the data that calcium carbide application significantly increased total

number of tillers pot-1 compared to that in the respective treatment of nitrogen fertilizer

alone. Maximum number of total tillers pot-1 (29.2) was observed in the treatment where

calcium carbide was applied @ 22.5 mg kg-1 along with full recommended dose of

nitrogen (60 mg kg-1 soil) while minimum in the control.

Calcium carbide, when applied without N fertilizer, did not affect number of

spikes pot-1 (number of spike bearing tillers). Treatment having calcium carbide

application @ 7.5 mg kg-1 soil with half of recommended dose of nitrogen (30 mg kg-

1soil), produced spikes even more than that of the treatment with full recommended dose

of nitrogen fertilizer but without calcium carbide. Maximum number of spikes pot-1 was

recorded in the treatments where calcium carbide was applied @ 15 or 22.5 mg kg-1 soil

in the presence of full recommended dose of N fertilizer as compared to treatment of

recommended N fertilizer alone. According to an estimate, pots treated with 22.5 mg

CaC2 kg-1 soil produced 35 % more number of spike bearing tillers in the presence of full

dose of nitrogen fertilizer than that of alone full dose of N fertilizer.

4.7.3.1.3 Spike length

Data regarding effect of rate of matrix-I formulated calcium carbide with and

without different doses of nitrogen fertilizer on spike length (cm) of wheat is summarized

in Fig.7.4. Spike length was significantly increased with increasing rate of N fertilizer.

However, calcium carbide application with either dose of nitrogen fertilizer further

increased the spike length compared with the respective alone N fertilizer treatment.

Maximum spike length (10.8 cm) was noted where N-CaC2 was applied @ 60-15 mg kg-1

soil (full recommended dose of nitrogen fertilizer-rate of CaC2). Data also revealed that

different rates of calcium carbide did not differ from each other in increasing spike

length.

4.7.3.1.4 Number of spikelets

Response of wheat in terms of number of spikelets spike-1 to different rates of

calcium carbide based formulation matrix-I with and without nitrogen fertilizer is

elaborated in Fig.7.5. A gradual increase in number of spikelets spike-1 was noted with

increasing rate of nitrogen fertilizer and it was further increased with the addition of

calcium carbide. Maximum number of spikelets spike-1 (17.8) was observed where

calcium carbide was applied @ 15 mg kg-1 soil along with full recommended does of

nitrogen fertilizer (60 mg kg-1 soil). In case of half and full recommended dose of N

fertilizer, almost similar number of spikelets per spike were observed with the addition of

calcium carbide. Calcium carbide without nitrogen fertilizer did not affect number of

spikelets spike-1 of wheat.

4.7.3.1.5 Number of grains

Combined effect of calcium carbide and nitrogen fertilizer application on number

of grains spike-1 is obvious from Fig.7.6. Number of grains spike-1 was significantly

increased with increasing rate of nitrogen fertilizer however addition of calcium carbide

further improved production of grains. Maximum number of grains spike-1 (54.5) was

noted where calcium carbide was applied @ 15 mg kg-1 soil with full recommended dose

of nitrogen. And it was minimum (44.3) in control where no calcium carbide and N

fertilizer were applied. Treatments with calcium carbide @ 15 or 22.5 mg kg-1 soil plus

half recommended N fertilizer produced grains comparable to that where full

recommended N was applied without CaC2. These results suggest that calcium carbide

has definite role in the production of more wheat grains either by improving N use

efficiency or stimulating growth promoting hormones.

4.7.3.1.6 Thousand grains weight

Effect of calcium carbide with and without nitrogen fertilizer on thousand grains

weight (g) of wheat is shown in Fig.7.7. 1000-grains weight was increased with

increasing rate of nitrogen fertilizer. Calcium carbide (matrix-I) application significantly

enhanced 1000-grains weight compared with respective fertilizer alone treatment.

Maximum and statistically similar weight was noted in treatments with CaC2 @ 15 mg

kg-1 + 30 mg kg-1 N or 15 or 22.5 mg kg-1 CaC2 + 60 mg kg-1 nitrogen. Irrespective to the

rate of N fertilizer applied, a reduction in 1000-grains weight was noted with the

application of calcium carbide @ 22.5 mg kg-1 soil compared with the treatment where it

was applied @ 15 mg kg -1 soil.

4.7.3.1.7 Biological yield

It is evident from the data (Fig.7.8) that increase in nitrogen fertilizer application

significantly increased the biological yield of wheat and addition of calcium carbide

further improved it. It was noted that maximum biological yield was produced by the

application of calcium carbide @ 15 mg kg-1 soil, followed by 7.5 mg kg-1 soil in the

presence of full recommended dose of nitrogen fertilizer. Treatment with half of

recommended nitrogen fertilizer plus 15 mg kg-1 CaC2 produced 8 % more biological

yield than that where full recommended N fertilizer was applied without CaC2. Compared

with 15 mg kg-1 soil CaC2, similar or less biological yield was observed with its higher

rate (22.5 mg kg-1 soil) when applied with either dose of nitrogen fertilizer.

4.7.3.1.8 Grain yield

Grain yield of wheat was also affected by rate of calcium carbide with and

without N fertilizer as is clear from the data summarized in Fig.7.9. It is clear from data

that grain yield was significantly increased with increasing rate of N fertilizer and

addition of calcium carbide. Maximum grain yield (31.2 g) was noted where calcium

carbide was applied @ 15 mg kg-1 soil, followed by 7.5 mg kg-1 soil in the presence of

full recommended dose of nitrogen fertilizer. Irrespective to the dose of nitrogen fertilizer

applied, a reduction trend in grain yield was observed with the application of high dose of

calcium carbide (22.5 mg kg-1) compared to the treatments where it was applied @ 15 mg

kg-1 soil. Treatment where half of recommended nitrogen fertilizer was applied with 15

mg kg-1 CaC2 produced grain yield statistically similar to that where full recommended N

fertilizer was applied without CaC2.

4.7.3.1.9 Nitrogen concentration in wheat straw and grain

Nitrogen concentration in both plant parts i.e. straw and grains was increased

significantly with increasing rate of nitrogen fertilizer (Table 7.1). Irrespective to the dose

of nitrogen fertilizer applied, addition of calcium carbide in the N fertilized pots

significantly increased N concentration in straw and grain however, straw N

concentration in treatments where CaC2 was applied @ 7.5 mg kg-1 soil did not differ

significantly from respective alone fertilizer treatment. Maximum N concentration in

grains as well as in straw was noted in the treatment where calcium carbide was applied

@ 15 mg kg-1 soil with full recommended dose of nitrogen fertilizer and it was

comparable with the treatment having 22.5 mg CaC2 kg-1 soil plus full recommended

dose of N fertilizer.

4.7.3.1.10 Nitrogen uptake by wheat straw and grain

Nitrogen application significantly increased N uptake of wheat straw and grains

(Table 7.1). Application of calcium carbide with half or full recommended dose of

nitrogen fertilizer further enhanced N uptake by both plant parts. Maximum N uptake was

noted where calcium carbide @ 15 mg kg-1 soil was applied with full dose of nitrogen

fertilizer. Compared with 15 mg CaC2 kg-1 soil, a reduction in N uptake was observed

where CaC2 was applied @ 22.5 mg kg-1 soil. Wheat straw and grain accumulated more

nitrogen in the treatment with half dose of nitrogen fertilizer plus CaC2 @ 15 mg kg-1 soil

than the treatment where recommended dose of N fertilizer was applied without CaC2.

4.7.3.1.11 Relative percent increase in parameters

Relative percent increase in plant growth and yield and analytical parameters of

wheat due to calcium carbide application at zero (control), half and full recommended

dose of nitrogen fertilizer is presented in Table 7.2. It is revealed from the data that

calcium carbide application increased grain yield by 16.2 %, 36.7 % and 29.7 % over

respective no calcium carbide treatment, when applied with zero, half and full

recommended dose of nitrogen fertilizer, respectively. Similarly in case of other

parameters calcium carbide comparatively gave more benefit where applied with half of

recommended nitrogen fertilizer than zero or full dose of it.

4.7.3.1.12 Nitrogen use efficiency

Application of calcium carbide in the form of matrix-I formulation significantly

improved agronomic efficiency, physiological efficiency and apparent nitrogen recovery

(Table 7.3). All of these efficiencies had maximum values in the treatments where

calcium carbide plus half of the recommended N dose was applied. The extents of these

efficiencies were increased from 11.6, 29.5 and 39.2 to 23.8, 34.5 and 68.9, respectively

due to application of calcium carbide along with half of recommended dose of nitrogen

fertilizer. In case of full recommended dose of nitrogen fertilizer though calcium carbide

application improved nitrogen use efficiency but up to less extent than that with half of

recommended dose of nitrogen fertilizer (Table 7.3).

.7.3.2 Discussion

Improvement in wheat growth and yield parameters and N uptake by different

plant parts with increasing rate of N fertilizer up to an optimum level is a well known fact

and has already been reported by Bakhsh et al. (1999) and Khan et al. (2000).

Cereal grain yield is the contribution of several components: spikes per unit area,

grains per spike and grain mass. The net effect of ethylene on grain yield depends on the

balance of positive, null and negative responses of individual yield components to

ethylene. Decrease in plant height with calcium carbide is a typical response of ethylene

produced in the soil due to CaC2 application (Dahnous et al., 1982; Wiersma et al.,

1986; Rajala and Peltonen-Sainio, 2001; Rajala et al., 2002 and Mahmood et al.,

2002). Increase in number of tillers and spikes per unit area with calcium carbide

application are owing to ethylene production and better N supply due to nitrification

inhibition. Cartwright and Waddington (1982), Sharma and Yadav (1996), Rajala

and Peltonen-Sainio (2001), Mahmood et al. (2002) and Yaseen et al. (2004) also

reported similar results of ethylene on tillering in cereals.

Increase in number of grains spike-1 and grain weight with the addition of

calcium carbide might be due to effective action of calcium carbide on oxidation

of NH4+ i.e. nitrification inhibition for certain period of time that leads to

prolonged stay of nitrogen in the soil and thus enhances the N economy of the

soil or stimulatory effect on certain other growth promoting hormones. However,

it can also be speculated that mixed nitrogen supply (ammonium-N and nitrate-N

both, instead of nitrate-N alone) also made the nitrogen nutrition of wheat plants

better and they took up more N compared to that where no CaC2 was applied.

This improved N economy of soil might help to produce more and bold grains.

Benefits of mixed nitrogen nutrition on plant growth and development are also

reported by Chen et al. (1998) and Ali et al. (2001).

It is revealed from the results that calcium carbide application with lower

dose of nitrogen fertilizer (30 mg kg-1 soil) improved most of the wheat growth

and yield parameters as well as N uptake almost to the same level as with full

recommended dose of nitrogen fertilizer applied without calcium carbide. This is

clear indication that calcium carbide application improved the N use by the

wheat plant. This also indicates existence of a lot of N losses due to nitrification

and denitrification under field conditions. That is why N use efficiency seldom

exceeds 40%. Moreover, results of this experiment also suggest that nitrification

inhibition and ethylene supply benefited the wheat crop most probably by

enhancing the N economy in the growth medium i.e. soil by minimizing N losses.

4.8 Experiment 8 Growth and Yield Response of Wheat to Soil Applied Calcium Carbide under Field Conditions 4.8.1 Introduction

Results of the previous experiments clearly demonstrate that calcium carbide

based formulations are slow releasing sources of acetylene and ethylene in the soil

environment. Consistent slow release of acetylene gas inhibits nitrification for certain

periods and thus delays the conversion of ammonium to nitrate and enhances N economy

of the soil that leads to increase fertilizer nitrogen use efficiency of crop plants. This

activity is not only limiting nitrogen losses via nitrification/denitrification and nitrate

leaching but also by maintaining mixed nitrogen nutrition of plants for longer period of

time. Ethylene is a gaseous phytohormone released from calcium carbide which is

produced by the reduction process of acetylene to ethylene. It has a marked effect on a

number of growth and developmental processes. The exogenous ethylene application has

quite different influence on plant growth than endogenously produced ethylene. It affects

cell division and elongation and thus affects the direction of cell expansion in cells of

young shoots. Plants treated with ethylene has stimulated cells expansion only laterally

and thus produce thick shoots (Alberts et al., 1989) that develops resistance against

lodging in lodging susceptible crop plants (Harms, 1986; Boutaraa, 1991).

Bhakhar-2002 is a tall growing wheat cultivar which has a very good yield

potential but more susceptible to lodging near maturity due to rain and/or light wind

impact than c.v Inqulab-91 (a fact reported by local farming community). In this

experiment both the wheat cultivars were sown to check their comparative response to

calcium carbide application against lodging. Another objective of the study was to

confirm the comparative effect of calcium carbide based formulations on growth and

yield parameters of wheat under field conditions. Three calcium carbide based

formulations were selected, those performed comparatively better in the previous

experiments and their effects on growth, yield and N use by wheat cultivars were studied

under field conditions.

4.8.2 Materials and Methods Methodology of the experiment is discussed in section 3.8 in Materials and

Methods chapter.

4.8.3 Results and Discussion

4.8.3.1 Results

This experiment was conducted in two consecutive years. The results reported

here is average of two years.

4.8.3.1.1 Plant height

Application of rate and types of calcium carbide based formulations significantly

affected plant height (cm) of wheat cultivars (Fig.8.1). A reduction in plant height of both

wheat cultivars was noted with increasing rate of calcium carbide in either formulation in

both the years. Plant height was maximum in treatments with no calcium carbide and

minimum where CaC2 was applied @ 45 kg ha-1 in the treatment of matrix-I formulation.

Matrix-I formulation affected plant height of wheat comparatively more than that of

matrix-II and paint coated calcium carbide. Treatments where calcium carbide was

applied @ 30 kg ha-1 (=15 mg kg-1 soil) did not show any significant difference in plant

height compared to that of 45 kg ha-1. As Bhakhar-2002 is a tall stature cultivar,

therefore, plants of this cultivar were taller than Inqulab-91. In the net shell CaC2

application reduced plant height by 6.9 and 4.8 % in Bhakhar-2002 and Inqulab-91,

respectively.

4.8.3.1.2 Number of tillers

All the three formulations of calcium carbide significantly increased total number

of tillers (Fig.8.2) and fertile – spike bearing tillers m-2 (Fig.8.3) in both wheat cultivars

compared to that where NPK fertilizers were applied without calcium carbide. Maximum

number of spike bearing tillers was observed where matrix-I formulation was applied @

30 kg ha-1 CaC2. Number of spikes m-2 of wheat was statistically similar in treatments

with paint coated and matrix-1I calcium carbide based formulations. Number of fertile

tillers in the plots treated with calcium carbide @ 45 kg ha-1 did not differ significantly

from that where it was applied @ 30 kg ha-1. It was further noted that cv Bukhar-2002

produced 10.9 % more number of fertile tillers than cv Inqulab-91. This indicates that

cultivars responded to calcium carbide application differently and Bhakhar-2002

responded more than Inqulab-91.

4.8.3.1.3 Thousand-grains weight

Application of different rates and types of calcium carbide based formulations

also affected 1000-grains weight of both wheat cultivars under field conditions (Fig.8.4).

It is evident from the data that calcium carbide application significantly increased 1000-

grains weight of wheat compared to that of NPK fertilizers alone. Maximum 1000-grains

weight was observed with matrix-I formulation followed by matrix-II and paint coated

calcium carbide. In all three formulations, CaC2 applied @ 30 kg ha-1 gave the best

results in improving 1000-grains weight of wheat. Among all the formulations, the

performance of CaC2 @ 45 kg ha-1 did not differ significantly from 30 kg ha-1 in

enhancing 1000-grains weight of both wheat cultivars. Compared to control, CaC2

application improved 1000-grains weight by 3.5 % and 1.3 % in Bhakhar-2002 and

Inqulab-91 cultivars, respectively.

4.8.3.1.4 Biological yield

About 25 to 32 % increase in biological yield (kg ha-1) of both wheat cultivars

was observed where calcium carbide was applied in different formulations with NPK

fertilizers compared to that of fertilizers alone (Fig.8.5). Calcium carbide formulations

performed the best in improving biological yield of wheat. The performance of

formulations can be presented in ranking order as matrix-I > matrix-II > paint coated

CaC2. In case of matrix-II and paint coated calcium carbide based formulations;

application of CaC2 @ 45 kg ha-1 produced more biological yield compared to that where

it was applied at lower rates. Maximum biological yield of both cultivars was observed in

the treatment where matrix-I was applied @ 30 kg CaC2 ha-1 in combination with

recommended NPK fertilizers. Estimated values indicate that 10.5 % more biological

yield was recorded in Bhakhar-2002 than Inqulab-91 wheat cultivar. This indicates that

extent of response of both the wheat cultivars to calcium carbide application was not

similar. This may be due to the reason that Bhakhar-2002 was a tall stature cultivar.

4.8.3.1.5 Straw yield

Response of both wheat cultivars to different rates and type of calcium carbide

based formulations regarding straw yield (kg ha-1) is presented in Fig.8.6. It is evident

from the results that application of calcium carbide significantly improved straw yield of

wheat. Maximum straw yield was recorded in the plots where calcium carbide was

applied @ 30 kg ha-1 in the form of matrix-I. It is also obvious from the data that straw

yield in the treatments of calcium carbide @ 45 kg ha-1 in the form of matrix-II and paint

coating did not differ from that where it was applied @ 30 kg ha-1 in the same

formulations. After attaining a climax in straw yield due to the application of matrix-I

formulation @ 30 kg ha-1 CaC2, a reduction trend in straw yield was observed when this

formulation was applied @ 45 kg ha-1 CaC2. Both the wheat cultivars showed almost

similar extent of response to calcium carbide application for straw yield. However,

Bhakhar-2002 produced relatively more straw than Inqulab-91, probably due to its tall

stature.

4.8.3.1.6 Grain yield

Differences in data values (Fig.8.7) demonstrate that calcium carbide application

had positive effect on grain yield (kg ha-1) of both the wheat cultivars. About 25 to 28 %

increase in grain yield was observed where calcium carbide was applied in different

formulations in combination with NPK fertilizers compared to that of NPK fertilizers

alone. Maximum grain yield was observed where CaC2 was applied @ 30 kg ha-1 as

matrix-I, followed by matrix-II and paint coated calcium carbide. Application of calcium

carbide as matrix-II or in paint coating, in rates of 30 and 45 kg ha-1, did not differ from

each other in improving grain yield of wheat cultivars. Overall, maximum grain yield was

observed in the treatment of matrix-I calcium carbide formulation applied @ 30 kg ha-1

compared to that of 45 kg ha-1. It was also observed that grain yield of both the wheat

cultivars (Inqulab-91 and Bhakhar-2002) in the plots treated with CaC2 @ 30 kg ha-1 did

not differ from that where it was applied @ 45 kg ha-1. In either case Bukhar-2002

produced about 5 % more grain yield than Inqulab-91 cultivar.

4.8.3.1.7 Lodging Index

Lodging index is the measure of extent of lodging. A high value of lodging index

indicates that the crop was lodged to a greater area and/or extent. Data regarding effect of

rate of calcium carbide application to lodging index of two wheat varieties Inqulab-

91(lodging resistant variety) and Bhakhar-2002 (lodging susceptible variety) is

summarized in Fig.8.8. In the 1st year of the experiment no lodging was observed even in

the control plot of Bhakhar-2002 due to unfavorable environmental conditions for

lodging. In the 2nd year (2007-2008), near crop maturity, due to rain and wind impact

lodging was occurred in those plots of Bhakhar-2002 where no calcium carbide was

applied. Calcium carbide application significantly reduced lodging however different

rates of CaC2 (15, 30 or 45 kg ha-1) were similar in their impact on lodging. The extent of

lodging in different treatment plots is presented in Table 8.1 and it is obvious that more

lodging was occurred in the control plots. It was also observed that lodging was more in

plots which were randomly situated on the sides of the field of experiment compared to

those which were in the interior of the field.

4.8.3.1.8 Nitrogen concentration in wheat straw and grains

Minimum nitrogen concentration in wheat straw and grains was observed in

treatments where NPK fertilizers were applied alone compared to the treatments having

addition of calcium carbide. Straw N concentration was increased significantly only

where calcium carbide was applied @ 30 or 45 kg ha-1 in either formulation (Fig.8.9).

Straw N concentration in treatment with CaC2 @ 15 kg ha-1 did not differ significantly

from that where only NPK fertilizers were applied. Grain N concentration was gradually

increased with increasing rate of calcium carbide application in all the three formulations

(Fig.8.10). Maximum N concentration in grains was observed in the treatment with

matrix-I formulation followed by matrix-II and paint coated calcium carbide. About 3.3

% more N concentration in straw and grain was observed in Inqulab-91 than Bhakhar-

2002 cultivar.

4.8.3.1.9 Nitrogen uptake by wheat straw and grains

Differences in nitrogen uptake by straw and grains of both wheat cultivars due to

application of different rates and type of calcium carbide based formulations are

presented in Fig.8.11 and Fig.8.12, respectively. It is evident from the data that calcium

carbide application significantly improved N uptake in straw and grains of wheat. In both

plant parts, maximum N uptake was recorded in the plots treated with matrix-I

formulation, followed by matrix-II and paint coated calcium carbide. Irrespective of the

type of formulation, calcium carbide applied @ 45 kg ha-1 did not significantly affected N

uptake in both straw and grain of wheat cultivars compared to that where it was applied

@ 30 kg ha-1. Therefore, it can be considered that calcium carbide application @ 30 kg

ha-1 proved the best among all the rates of application of calcium carbide regarding N

uptake by wheat straw and grain.

4.8.3.1.10 Nitrate-N concentration in soil

Concentration of nitrate-N in soil was determined 8 weeks after calcium carbide

application from each field plots and data on average of 6 repeats (3 from each cultivar

plots) is presented in Fig.8.13. Nitrate-N concentration in the soil was significantly

decreased with increasing rate of calcium carbide. Maximum soil nitrate-N concentration

was recorded in the control where no calcium carbide was applied however it was

minimum in the treatment where calcium carbide was applied @ 45 kg ha-1 in the form of

matrix-I formulation.

4.8.3.1.11 Ammonium-N concentration in soil

A clear effect of calcium carbide on type of nitrogen concentration was observed.

Calcium carbide application significantly increased concentration of ammonical nitrogen

(NH4+) in the soil (Fig.8.14). Effect of calcium carbide on type of nitrogen in soil shows

that ammonium-N concentration in soil increased gradually with increasing rate of CaC2

applied in either formulation. Maximum NH4+-N was noted in the treatment of matrix-I

followed by matrix-II and paint coated calcium carbide. Minimum NH4+-N concentration

was in the treatment where NPK fertilizers were applied without calcium carbide.

4.8.3.2 Discussion

The results of the previous pot experiments with different doses of calcium

carbide based formulations are in total agreement with the results obtained under field

conditions. The obvious effect of calcium carbide application on plant growth was noted

by changing the pattern of growth response. Reduction in plant height and increase in

total as well spike bearing tillers of wheat with the application of calcium carbide based

formulations might be due to the influence of acetylene and ethylene gases released from

calcium carbide in the soil environment. Reduction in plant height of spring cereals due

to ethylene has already been reported by Dahnous et al. (1982), Wiersma et al. (1986),

Rajala and Peltonen-Sainio (2001), Rajala et al. (2002) and Mahmood et al. (2002).

Many workers including Cartwright and Waddington (1982), Sharma and Yadav (1996),

Rajala and Peltonen-Sainio (2001), Mahmood et al. (2002) and Yaseen et al. (2004) also

reported similar impact of ethylene on tillering in cereals.

Increase in straw yield might be attributed to more number of tillers, which were

significantly enhanced by the application of CaC2. These results are in line with the

findings of Brown and Early (1973), Dahnous et al. (1982), Mahmood et al. (2002) and

Yaseen et al. (2004, 2005, 2006). Grain production and quality is dependent on a number

of factors such as tillering, nutrient use efficiency, nutrient balance and photosynthate

translocation within plant body etc. All the above factors have direct relationship with

root growth. Calcium carbide has definite effect on root growth. Therefore ethylene

produced from CaC2 stimulated the early root growth and thus positively influenced all

the above mentioned processes. Moreover, higher production of wheat grain directly

depends upon number, size and boldness of grains. Therefore increase in 1000-grains

weight in this study most probably was due to increase in boldness of grain which is well

documented effect of ethylene on grain formation (Brown and Early, 1973)

Owing to calcium carbide application, increase in number of spike bearing tillers

(fertile tillers) per unit area, better root growth which in turn uptake more nutrients from

soil for healthy grain formation, prolonged nitrogen supply due to nitrification inhibition

and mixed nitrogen nutrition instead of nitrate alone are some of the factors which

contribute directly or indirectly to increase in grain yield.

Acetylene as a potent nitrification inhibitor is also well documented by Walter et

al. (1979), Banerjee and Mosier (1989), Bronson et al. (1992), Smith et al. (1993), Chen

et al. (1994) and Freney et al. (2000). In the present experiment presence of more NH4+-

N and less soil NO3- -N in the soil treated with calcium carbide based formulations

compared to that of NPK fertilizers alone indicates that calcium carbide application

significantly inhibited nitrification under field conditions which in turn markedly reduced

N losses from soil. This is obvious from the enhanced N uptake values in straw and

grains from CaC2 treated soil. Improvement in N uptake by different crops due to the

application of CaC2 and other sources of acetylene is also reported by Yaseen et al.

(2004), Mahmood et al. (2005) and Kashif et al. (2007).

Lodging is another grain yield contributing factor. It can reduce 10-50 % grain

yield. Reduction in lodging of wheat crop due to calcium carbide application is attributed

to ethylene produced in the soil environment from CaC2. Control on lodging in cereals

with exogenous application of ethylene is also reported by Dahnous et al. (1982), Harms

(1986), Simmons et al. (1988), Boutaraa (1991) and Lauer (1991). Less lodging might be

due to increase in the strength of stem which is well documented effect of ethylene

(Alberts et al., 1989) released from ethephon and calcium carbide.

Overall results of all the experiments indicate that calcium carbide application

have a pronounced and beneficial effect on wheat growth and yield parameters. Out of

different calcium carbide based formulations matrix-I was the best in improving

economical yield of wheat when applied two weeks after sowing at 8 cm depth into the

soil.

60

62

64

66

68

70

72

74

76

78

80

0-0 60-0 60-7.5 60-15 60-22.5 60-30 60-37.5

Nitrogen - Calcium carbide (mg kg-1 soil)

Plan

t hei

ght (

cm)

Fig. 4.1 Effect of rate of encapsulated calcium carbide on plant height of wheat.

(Detailed statistical analysis is given in Annexure I)

5

10

15

20

25

30

0-0 60-0 60-7.5 60-15 60-22.5 60-30 60-37.5

Nitrogen - Calcium carbide (mg kg-1 soil)

Num

ber o

f tille

rs p

ot-1

Fig. 4.2 Effect of rate of encapsulated calcium carbide on number of tillers of wheat.

(Detailed statistical analysis is given in Annexure I)

Fig. 4.3 Wheat growth pattern in response to encapsulated calcium carbide application (a) NPK alone (b) NPK plus ECC @ 22.5 mg kg-1 soil.

(a) (b)

0

2

4

6

8

10

12

14

0-0 60-0 60-7.5 60-15 60-22.5 60-30 60-37.5

Nitrogen - Calcium carbide (mg kg-1 soil)

Roo

t wei

ght (

g po

t-1)

Fig.4.4 Effect of rate of encapsulated calcium carbide on root weight of wheat.

(Detailed statistical analysis is given in Annexure I)

10

15

20

25

30

35

40

45

0-0 60-0 60-7.5 60-15 60-22.5 60-30 60-37.5

Nitrogen - Calcium carbide (mg kg-1 soil)

Stra

w y

ield

(g p

ot-1)

Fig.4.5 Effect of rate of encapsulated calcium carbide on straw yield of wheat.

(Detailed statistical analysis is given in Annexure I)

5

10

15

20

25

30

0-0 60-0 60-7.5 60-15 60-22.5 60-30 60-37.5

Nitrogen - Calcium carbide (mg Kg-1 soil)

Gra

in y

ield

(g p

ot-1)

Fig.4.6 Effect of rate of encapsulated calcium carbide on grain yield of wheat.

(Detailed statistical analysis is given in Annexure I)

200

300

400

500

600

700

800

900

1000

0-0 60-0 60-7.5 60-15 60-22.5 60-30 60-37.5

Nitrogen - Calcium carbide (mg kg-1 soil)

Nitr

ogen

upt

ake

(mg

pot-1)

Fig.4.7 Effect of rate of encapsulated calcium carbide on nitrogen uptake by

wheat tops at maturity. (Detailed statistical analysis is given in Annexure I)

62

64

66

68

70

72

74

76

78

80

T1 T2 T3 T4 T5

Treatments

Plan

t hei

ght (

cm)

Fig.4.8 Effect of time of application of encapsulated calcium carbide on plant

height of wheat. (Detailed statistical analysis is given in Annexure II)

0

10

20

30

T1 T2 T3 T4 T5

Treatments

Num

ber o

f tille

rs p

ot-1

Fig.4.9 Effect of time of application of encapsulated calcium carbide on number of

tillers of wheat. (Detailed statistical analysis is given in Annexure II)

T1= P&K; T2= NPK; T3=NPK + ECC applied at sowing; T4= NPK + ECC applied 2 weeks after sowing; T5= NPK + ECC applied 4 weeks after sowing * NPK and ECC were applied @ 60:45:30 and 22.5 mg kg-1 soil, respectively

0

2

4

6

8

10

12

T1 T2 T3 T4 T5

Treatments

Roo

t wei

ght (

g po

t-1)

Fig.4.10 Effect of time of application of encapsulated calcium carbide on root

weight of wheat. (Detailed statistical analysis is given in Annexure II)

0

10

20

30

40

50

T1 T2 T3 T4 T5

Treatments

Stra

w y

ield

(g p

ot-1)

Fig.4.11 Effect of time of application of encapsulated calcium carbide on straw

yield of wheat. (Detailed statistical analysis is given in Annexure II)

T1= P&K; T2= NPK; T3=NPK + ECC applied at sowing; T4= NPK + ECC applied 2 weeks after sowing; T5= NPK + ECC applied 4 weeks after sowing * NPK and ECC were applied @ 60:45:30 and 22.5 mg kg-1 soil, respectively

0

10

20

30

T1 T2 T3 T4 T5

Treatments

Gra

in y

ield

(g p

ot-1)

Fig.4.12 Effect of time of application of encapsulated calcium carbide on grain yield

of wheat. (Detailed statistical analysis is given in Annexure II)

0

100

200

300

400

500

600

700

800

900

1000

T1 T2 T3 T4 T5

Treatments

Tota

l N u

ptak

e (m

g po

t-1 )

Fig.4.13 Effect of time of application of encapsulated calcium carbide on total N

uptake of wheat. (Detailed statistical analysis is given in Annexure II)

T1= P&K; T2= NPK; T3=NPK + ECC applied at sowing; T4= NPK + ECC applied 2 weeks after sowing; T5= NPK + ECC applied 4 weeks after sowing * NPK and ECC were applied @ 60:45:30 and 22.5 mg kg-1 soil, respectively

(a)

0

5000

10000

15000

20000

25000

30000

3 7 21 35 49 63 77 91

Time after CaC2 application (days)

Acet

ylen

e co

nten

t (nm

ol k

g-1 s

oil)

Control EncapsulatedBee w ax coated paraff in w ax coatedpaint coated Matrix-IMatrix-II Matrix-III

(b)

0

100

200

300

400

500

600

3 7 21 35 49 63 77 91

Time after CaC2 application (days)

Ethy

lene

(nm

ol k

g-1 s

oil)

Control EncapsulatedBee w ax coated paraff in w ax coatedPaint coated Matrix-IMatrix-II Matrix-III

Fig.4.14 Effect of calcium carbide based formulations on the release of (a) acetylene (b) ethylene content in the soil. (Detailed statistical analysis is given in Annexure III)

*In either formulation CaC2 was applied @ 22.5 mg kg-1 soil

(a)

0

2

4

6

8

10

12

14

16

18

3 7 21 35 49 63 77 91

Time after CaC2 application (days)

Acet

ylen

e flu

x (n

g m

-2 m

in-1)

Control EncapsulatedBee w ax coated paraff in w ax coatedpaint coated Matrix-IMatrix-II Matrix-III

(b)

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

0.40

3 7 21 35 49 63 77 91

Time after CaC2 application (days)

Ethy

lene

flux

(ng

m-2 m

in-1)

Control EncapsulatedBee w ax coated paraff in w ax coatedPaint coated Matrix-IMatrix-II Matrix-III

Fig.4.15 Effect of calcium carbide based formulations on the (a) acetylene (b)

ethylene flux from the soil surface. *In either formulation CaC2 was applied @ 22.5 mg kg-1 soil

(a)

0

50

100

150

200

250

3 7 21 35 49 63 77 91

Time after application (days)

Amm

oniu

m-N

(ug

N g-1

soi

l)

Control EncapsulatedBee w ax coated Paraffin w ax coatedPaint coated Matrix-IMatrix-II Matrix-III

(b)

020406080

100120140160180200

3 7 21 35 49 63 77 91

Time after application (days)

Nitr

ate-

N (u

g N

g-1 s

oil)

Control EncapsulatedBee w ax coated Paraff in w ax coatedPaint coated Matrix-IMatrix-II Matrix-III

Fig.4.16 Effect of calcium carbide based formulations on soil (a) ammonium-

N (b) nitrate-N content at different time intervals. (Detailed statistical analysis is given in Annexure III)

*In either formulation CaC2 was applied @ 22.5 mg kg-1 soil

(a)

0

1

2

3

4

5

6

7

T1 T2 T3 T4 T5 T6 T7 T8

Calcium carbide formulations

Mea

n em

erge

nce

time

(day

s)

(b)

0

1

1

2

2

3

3

4

T1 T2 T3 T4 T5 T6 T7 T8

Calcium carbide formulations

Emer

genc

e R

ate

Inde

x

Fig.4.17 Effect of calcium carbide based formulations on (a) mean emergence time (b) emergence rate index of wheat seedlings. (Detailed statistical analysis is given in Annexure IV-A)

T1= control; T2 = Encapsulated CaC2; T3 = Bee wax coated CaC2; T4 = Paraffin wax coated CaC2, T5 = Paint coated CaC2; T6 = Matrix-I; T7 = Matrix-II; T8 = Matrix-III *All formulations were applied @ 22.5 mg CaC2 kg-1 soil

0

50

100

150

200

250

T1 T2 T3 T4 T5 T6 T7 T8

Calcium carbide formulations

Fres

h bi

omas

s (m

g pl

ant-1)

3 days after sow ing 6 days after sow ing

12 days after sow ing 15 days after sow ing

Fig.4.18 Effect of calcium carbide based formulations on fresh biomass weight of wheat seedlings 3, 6, 12 and 15 days after sowing. (Detailed statistical analysis is given in Annexure IV-A)

T1= control; T2 = Encapsulated CaC2; T3 = Bee wax coated CaC2; T4 = Paraffin wax coated CaC2, T5 = Paint coated CaC2; T6 = Matrix-I; T7 = Matrix-II; T8 = Matrix-III *All formulations were applied @ 22.5 mg CaC2 kg-1 soil

A B C D

Fig.4.19 Effect of calcium carbide based formulations on wheat seedling growth 3 days after sowing. [ A) Control B) Encapsulated CaC2 C) Bee wax coated CaC2 D) Matrix-I]

(a)

0

2

4

6

8

10

12

14

16

T1 T2 T3 T4 T5 T6 T7 T8

Calcium carbide formulations

Roo

t and

Sho

ot le

ngth

(cm

)

Root length (cm) Shoot length (cm)

(b)

0

20

40

60

80

100

120

140

160

T1 T2 T3 T4 T5 T6 T7 T8Calcium carbide formulations

Roo

t and

Sho

ot w

eigh

t (m

g pl

ant-1

)

Root w t. (mg) Shoot w t. (mg)

Fig.4.20 Effect of calcium carbide based formulations on root and shoot (a) length (b)

weight of wheat seedlings 15 days after sowing. (Detailed statistical analysis is given in Annexure IV-A)

T1= control; T2 = Encapsulated CaC2; T3 = Bee wax coated CaC2; T4 = Paraffin wax coated CaC2, T5 = Paint coated CaC2; T6 = Matrix-I; T7 = Matrix-II; T8 = Matrix-III

*All formulations were applied @ 22.5 mg CaC2 kg-1 soil

A B C D

Fig.4.21 Effect of calcium carbide based formulations on wheat root growth 15 days after sowing. [ A) Control B) Encapsulated CaC2 C) Bee wax coated CaC2 D) Matrix-I]

0.00.20.40.60.81.01.21.41.61.82.0

T1 T2 T3 T4 T5 T6 T7 T8

Calcium carbide formulations

Roo

t:sho

ot ra

tio

Root/shoot by length Root/shoot by w eight

Fig.4.22 Effect of calcium carbide based formulations on root : shoot ratios by length and weight of wheat seedlings 15 days after sowing. (Detailed statistical analysis is given in Annexure IV-A)

T1= control; T2 = Encapsulated CaC2; T3 = Bee wax coated CaC2; T4 = Paraffin wax coated CaC2, T5 = Paint coated CaC2; T6 = Matrix-I; T7 = Matrix-II; T8 = Matrix-III *All formulations were applied @ 22.5 mg CaC2 kg-1 soil

(a)

0

2

4

6

Control 7.5 15 22.5

Rate of matrix-I (mg CaC2 kg-1 soil)

Mea

n em

erge

nce

time

(day

s)

(b)

0

1

2

3

4

Control 7.5 15 22.5

Rate of matrix-I (mg CaC2 kg-1 soil)

Emer

genc

e ra

te in

dex

Fig.4.23 Effect of different doses of matrix-I based calcium carbide on (a) mean

emergence time (b) emergence rate index of wheat seedlings. (Detailed statistical analysis is given in Annexure IV-B)

0

10

20

30

40

50

60

70

80

90

T1 T2 T3 T4 T5 T6 T7 T8 T9

Treatments

Plan

t hei

ght (

cm)

Fig.5.1 Effect of calcium carbide based formulations on plant height of wheat.

(Detailed statistical analysis is given in Annexure V)

0

5

10

15

20

25

30

35

T1 T2 T3 T4 T5 T6 T7 T8 T9

Treatments

Num

ber o

f tille

rs p

ot-1

Total tillers Fertile tillers

Fig.5.2 Effect of calcium carbide based formulations on number of tillers of wheat.

(Detailed statistical analysis is given in Annexure V) T1= P&K; T2 = NPK; T3 = NPK + encapsulated CaC2; T4 = NPK + bee wax coated CaC2; T5 = NPK + paraffin wax coated CaC2, T6 = NPK + paint coated CaC2; T7 = NPK + matrix-I; T8 = NPK + matrix-II; T9 = NPK + matrix-III *In either formulation CaC2 was applied @ 22.5 mg kg-1 soil

0

2

4

6

8

10

12

14

T1 T2 T3 T4 T5 T6 T7 T8 T9

Treatments

Roo

t wei

ght (

g po

t-1)

Fig.5.3 Effect of calcium carbide based formulations on root weight of wheat.

(Detailed statistical analysis is given in Annexure V)

30

35

40

45

50

55

T1 T2 T3 T4 T5 T6 T7 T8 T9

Treatments

1000

-gra

ins

wei

ght (

g)

Fig.5.4 Effect of calcium carbide based formulations on 1000-grains weight of

wheat. (Detailed statistical analysis is given in Annexure V)

T1= P&K; T2 = NPK; T3 = NPK + encapsulated CaC2; T4 = NPK + bee wax coated CaC2; T5 = NPK + paraffin wax coated CaC2, T6 = NPK + paint coated CaC2; T7 = NPK + matrix-I; T8 = NPK + matrix-II; T9 = NPK + matrix-III *In either formulation CaC2 was applied @ 22.5 mg kg-1 soil

(a)

0

10

20

30

40

50

60

70

80

T1 T2 T3 T4 T5 T6 T7 T8 T9

Treatments

Biol

ogic

al y

ield

(g p

ot-1)

(b)

0

5

10

15

20

25

30

35

T1 T2 T3 T4 T5 T6 T7 T8 T9

Treatments

Gra

in y

ield

(g p

ot-1)

Fig.5.5 Effect of calcium carbide based formulations on (a) biological yield (b) grain

yield of wheat. (Detailed statistical analysis is given in Annexure V)

T1= P&K; T2 = NPK; T3 = NPK + encapsulated CaC2; T4 = NPK + bee wax coated CaC2; T5 = NPK + paraffin wax coated CaC2, T6 = NPK + paint coated CaC2; T7 = NPK + matrix-I; T8 = NPK + matrix-II; T9 = NPK + matrix-III *In either formulation CaC2 was applied @ 22.5 mg kg-1 soil

(a)

0.20

0.25

0.30

0.35

0.40

0.45

0.50

0.55

T1 T2 T3 T4 T5 T6 T7 T8 T9

Treatments

N c

once

ntra

tion

in ro

ot (%

)

(b)

0.30

0.35

0.40

0.45

0.50

0.55

0.60

0.65

T1 T2 T3 T4 T5 T6 T7 T8 T9

Treatments

N c

once

ntra

tion

in s

traw

(%)

(Continued to next page)

(c)

1.0

1.2

1.4

1.6

1.8

2.0

2.2

2.4

T1 T2 T3 T4 T5 T6 T7 T8 T9

Treatments

N c

once

ntra

tion

in g

rain

(%)

Fig.5.6 Effect of calcium carbide based formulations on N concentration in wheat (a) root (b) straw and (c) grains of wheat. (Detailed statistical analysis is given in Annexure V)

T1= P&K; T2 = NPK; T3 = NPK + encapsulated CaC2; T4 = NPK + bee wax coated CaC2; T5 = NPK + paraffin wax coated CaC2, T6 = NPK + paint coated CaC2; T7 = NPK + matrix-I; T8 = NPK + matrix-II; T9 = NPK + matrix-III *In either formulation CaC2 was applied @ 22.5 mg kg-1 soil

(a)

0

10

20

30

40

50

60

70

T1 T2 T3 T4 T5 T6 T7 T8 T9

Treatments

N u

ptak

e by

root

(mg

pot-1)

(b)

50

100

150

200

250

300

T1 T2 T3 T4 T5 T6 T7 T8 T9

Treatments

N u

ptak

e by

stra

w (m

g po

t-1)

(Continued to next page)

(c)

100

200

300

400

500

600

700

800

T1 T2 T3 T4 T5 T6 T7 T8 T9

Treatments

N u

ptak

e by

gra

in (m

g po

t-1)

Fig.5.7 Effect of calcium carbide based formulations on N uptake by wheat (a) root (b) straw and (c) grains. (Detailed statistical analysis is given in Annexure V)

T1= P&K; T2 = NPK; T3 = NPK + encapsulated CaC2; T4 = NPK + bee wax coated CaC2; T5 = NPK + paraffin wax coated CaC2, T6 = NPK + paint coated CaC2; T7 = NPK + matrix-I; T8 = NPK + matrix-II; T9 = NPK + matrix-III *In either formulation CaC2 was applied @ 22.5 mg kg-1 soil

0

200

400

600

800

1000

1200

T1 T2 T3 T4 T5 T6 T7 T8 T9

Treatments

Tota

l N u

ptak

e (m

g po

t-1)

Fig.5.8 Effect of calcium carbide based formulations on total N uptake by wheat.

(Detailed statistical analysis is given in Annexure V)

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

T1 T2 T3 T4 T5 T6 T7 T8 T9Treatments

N u

ptak

e

Roots Straw Grains

Fig.5.9 Effect of calcium carbide based formulations on N partitioning in

different plant parts of wheat at maturity. T1= P&K; T2 = NPK; T3 = NPK + encapsulated CaC2; T4 = NPK + bee wax coated CaC2; T5 = NPK + paraffin wax coated CaC2, T6 = NPK + paint coated CaC2; T7 = NPK + matrix-I; T8 = NPK + matrix-II; T9 = NPK + matrix-III *In either formulation CaC2 was applied @ 22.5 mg kg-1 soil

0

10

20

30

40

50

60

T1 T2 T3 T4 T5 T6 T7 T8 T9

Treatments

Min

eral

N (p

pm)

Nitrate-N Ammonium-N

Fig.5.10 Effect of calcium carbide based formulations on soil mineral nitrogen after 8 weeks of calcium carbide application to wheat crop. (Detailed statistical analysis is given in Annexure V)

T1= P&K; T2 = NPK; T3 = NPK + encapsulated CaC2; T4 = NPK + bee wax coated CaC2; T5 = NPK + paraffin wax coated CaC2, T6 = NPK + paint coated CaC2; T7 = NPK + matrix-I; T8 = NPK + matrix-II; T9 = NPK + matrix-III *In either formulation CaC2 was applied @ 22.5 mg kg-1 soil

Table 6.1 Effect of rate and application depth of calcium carbide (matrix-I) on plant height (cm) of wheat.

Calcium carbide application depth (cm) Rate of CaC2 (mg kg-1) 0 4 8 12

Mean

0 92.5 a* 92.6 a 92.3 a 92.5 a 92.5 A 7.5 91.9 ab 91.9 abc 90.7 cd 90.6 d 91.3 B 15 92.4 a 90.8 bcd 89.3 e 89.1 e 90.4 C

22.5 92.1 a 89.7 de 88.6 e 88.6 e 89.7 D Mean 92.2 A 91.2 B 90.2 C 90.2 C

Table 6.2 Effect of rate and application depth of calcium carbide (matrix-I) on total

number of tillers pot-1 of wheat. Calcium carbide application depth (cm) Rate of CaC2

(mg kg-1) 0 4 8 12

Mean

0 20.2 f* 21.5 f 21.2 f 22.0 ef 21.2 C 7.5 21.5 ef 23.8 de 25.8 cd 27.8 bc 24.7 B 15 21.0 f 25.2 d 28.2 ab 29.2 ab 25.9 A

22.5 20.8 f 25.8 cd 28.8 ab 30.2 a 26.4 A Mean 20.9 D 24.1 C 26.0 B 27.3 A

Table 6.3 Effect of rate and application depth of calcium carbide (matrix-I) on number of

fertile tillers pot-1 of wheat. Calcium carbide application depth (cm) Rate of CaC2

(mg kg-1) 0 4 8 12

Mean

0 15.5 h* 17.5 fgh 17.5 fgh 18.0 efgh 17.2 C 7.5 16.8 gh 19.8 cdef 21.0 bcd 23.0 ab 19.4 B 15 16.5 gh 21.8 abc 23.8 a 20.0 cdef 20.8 A

22.5 16.2 gh 22.0 abc 20.5 bcde 18.8 defg 19.1 B Mean 16.2 C 19.9 B 21.3 A 19.2 B

Table 6.4 Effect of rate and application depth of calcium carbide (matrix-I) on number of

unfertile tillers pot-1 of wheat. Calcium carbide application depth (cm) Rate of CaC2

(mg kg-1) 0 4 8 12 Mean

0 4.8 c* 4.0 c 3.8 c 4.0 c 4.0 C 7.5 4.8 c 4.0 c 4.8 c 4.8 c 5.3 B 15 4.5 c 3.5 c 4.5 c 9.2 b 5.2 BC

22.5 4.5 c 3.8 c 8.2 b 11.5 a 7.3 A Mean 4.7 B 4.1 B 4.9 B 8.1 A

*Means sharing a common letter(s) in (a) table body (non bold) (b) last column (c) last row are not significantly different at p < 0.05 by LSD test.

Table 6.5 Effect of rate and application depth of calcium carbide (matrix-I) on 1000-grains weight (g) of wheat.

Calcium carbide application depth (cm) Rate of CaC2 (mg kg-1)

0 4 8 12

Mean

0 46.0 fg* 46.0 fg 46.0 fg 45.8 g 45.8 C

7.5 45.6 g 46.3 efg 47.5 bcde 48.4 abc 47.9 B

15 45.4 g 47.8 abcd 48.8 a 47.2 cdef 47.7 A

22.5 45.9 fg 48.6 ab 47.2 cdef 46.6 defg 46.8 B

Mean 45.8 C 47.0 B 47.6 A 46.9 B

Table 6.6 Effect of rate and application depth of calcium carbide (matrix-I) on biological

yield (g pot-1) of wheat. Calcium carbide application depth (cm) Rate of CaC2

(mg kg-1) 0 4 8 12

Mean

0 49.3 hij* 47.5 j 52.8 ghi 50.6 g 51.0 C 7.5 49.3 hij 54.2 gh 67.1 def 71.6 cd 60.6 B

15 49.4 hij 64.1 f 83.4 a 70.6 cde 66.9 A

22.5 48.8 ij 74.4 bc 79.3 ab 65.7 ef 67.0 A Mean 49.2 D 60.0 C 70.6 A 65.6 B

Table 6.7 Effect of rate and application depth of calcium carbide (matrix-I) on grain yield

(g pot-1) of wheat. Calcium carbide application depth (cm) Rate of CaC2

(mg kg-1) 0 4 8 12

Mean

0 22.6 fgh* 21.3 h 22.3 fgh 23.8 fg 22.5 C

7.5 22.1 fgh 24.0 f 30.1 de 31.7 bcd 27.0 B 15 22.0 gh 29.0 e 35.4 a 30.5 cde 29.2 A

22.5 21.9 gh 32.0 bc 33.4 b 29.8 e 29.3 A

Mean 22.1 D 26.6 C 30.3 A 29.0 B *Means sharing a common letter(s) in (a) table body (non bold) (b) last column (c) last row are not significantly different at p < 0.05 by LSD test.

Table 6.8 Effect of rate and application depth of calcium carbide (matrix-I) on nitrogen concentration (%) in wheat straw.

Calcium carbide application depth (cm) Rate of CaC2 (mg kg-1) 0 4 8 12

Mean

0 0.53 ef* 0.52 ef 0.52 ef 0.52 f 0.52 C 7.5 0.52 ef 0.54 de 0.56 bcd 0.57 ab 0.55 B 15 0.52 ef 0.56 cd 0.57 abc 0.59 a 0.56 A

22.5 0.53 ef 0.57 abc 0.58 a 0.58 a 0.56 A Mean 0.53 D 0.55 C 0.56 B 0.57 A

Table 6.9 Effect of rate and application depth of calcium carbide (matrix-I) on nitrogen

concentration (%) in wheat grain. Calcium carbide application depth (cm) Rate of CaC2

(mg kg-1) 0 4 8 12 Mean

0 2.11 f* 2.11 f 2.12 f 2.12 f 2.11 D 7.5 2.12 f 2.18 de 2.19 cd 2.16 e 2.16 C 15 2.12 f 2.20 cd 2.27 b 2.28 ab 2.21 B

22.5 2.13 f 2.21 c 2.30 a 2.29 a 2.23 A Mean 2.12 C 2.17 B 2.22 A 2.21 A

Table 6.10 Effect of rate and application depth of calcium carbide (matrix-I) on nitrogen

uptake (g pot-1) by wheat straw. Calcium carbide application depth (cm) Rate of CaC2

(mg kg-1) 0 4 8 12 Mean

0 0.14 g* 0.14 g 0.16 fg 0.16 fg 0.15 C 7.5 0.14 g 0.16 f 0.20 e 0.23 cd 0.18 B 15 0.14 g 0.19 e 0.27 a 0.23 c 0.21 A

22.5 0.14 fg 0.24 bc 0.26 ab 0.21 de 0.21 A Mean 0.14 D 0.18 C 0.22 B 0.28 A

Table 6.11 Effect of rate and application depth of calcium carbide (matrix-I) on nitrogen

uptake (g pot-1) by wheat grain. Calcium carbide application depth (cm) Rate of CaC2

(mg kg-1) 0 (at surface)

4 8 12 Mean

0 0.45 fg* 0.45 g 0.47 fg 0.50 ef 0.47 C 7.5 0.47 fg 0.52 e 0.66 cd 0.68 bc 0.58 B 15 0.47 fg 0.46 d 0.80 a 0.69 bc 0.65 A

22.5 0.47 fg 0.71 b 0.77 a 0.68 bc 0.66 A Mean 0.46 D 0.58 C 0.67 A 0.64 B

*Means sharing a common letter(s) in (a) table body (non bold) (b) last column (c) last row are not significantly different at p < 0.05 by LSD test.

40

50

60

70

80

90

100

0-0 0-7.5 0-150-22.5 30-0

30-7.530-15

30-22.5 60-060-7.5

60-1560-22.5

Nitrogen-calcium carbide (mg kg-1 soil)

Pla

nt h

eigh

t (cm

)

Fig.7.1 Effect of different rates of matrix-I formulated calcium carbide with and

without N fertilizer on plant height of wheat. (Detailed statistical analysis is given in Annexure VII)

05

10152025

3035

0-0 0-7.5 0-150-22.5 30-0

30-7.530-15

30-22.5 60-060-7.5

60-1560-22.5

Nitrogen-calcium carbide (mg kg-1 soil)

Num

ber o

f till

ers

pot-1

Fig.7.2 Effect of different rates of matrix-I formulated calcium carbide with and

without N fertilizer on total number of tillers of wheat. (Detailed statistical analysis is given in Annexure VII)

0

5

10

15

20

25

30

0-0 0-7.5 0-150-22.5 30-0

30-7.530-15

30-22.5 60-060-7.5

60-1560-22.5

Nitrogen-calcium carbide (mg kg-1 soil)

Num

ber o

f fer

tile

tille

rs p

ot-1

Fig.7.3 Effect of different rates of matrix-I formulated calcium carbide with and

without N fertilizer on number of fertile tillers of wheat. (Detailed statistical analysis is given in Annexure VII)

56789

101112

0-00-7.5 0-15

0-22.5 30-030-7.5

30-1530-22.5 60-0

60-7.560-15

60-22.5

Nitrogen-calcium carbide (mg kg-1 soil)

Spi

ke le

ngth

(cm

)

Fig.7.4 Effect of different rates of matrix-I formulated calcium carbide with and

without N fertilizer on spike length of wheat. (Detailed statistical analysis is given in Annexure VII)

579

1113151719

0-0 0-7.5 0-150-22.5 30-0

30-7.530-15

30-22.5 60-060-7.5

60-1560-22.5

Nitrogen-calcium carbide (mg kg-1 soil)

Num

ber o

f spi

kele

ts s

pike

-1

Fig.7.5 Effect of different rates of matrix-I formulated calcium carbide with and

without N fertilizer on number of spikelets spike-1 of wheat. (Detailed statistical analysis is given in Annexure VII)

10

20

30

40

50

60

0-00-7.5 0-15

0-22.5 30-030-7.5

30-1530-22.5 60-0

60-7.560-15

60-22.5

Nitrogen-calcium carbide (mg kg-1 soil)

Num

ber o

f gra

ins

spik

e-1

Fig.7.6 Effect of different rates of matrix-I formulated calcium carbide with and

without N fertilizer on number of grains spike-1 of wheat. (Detailed statistical analysis is given in Annexure VII)

30

35

40

45

50

55

0-00-7.5 0-15

0-22.5 30-030-7.5

30-1530-22.5 60-0

60-7.560-15

60-22.5

Nitrogen-calcium carbide (mg kg-1 soil)

1000

-gra

ins

wei

ght (

g)

Fig.7.7 Effect of different rates of matrix-I formulated calcium carbide with and

without N fertilizer on 1000-grains weight of wheat. (Detailed statistical analysis is given in Annexure VII)

01020304050607080

0-00-7.5 0-15

0-22.5 30-030-7.5

30-1530-22.5 60-0

60-7.560-15

60-22.5

Nitrogen-calcium carbide (mg kg-1 soil)

Bio

logi

cal y

ield

(g p

ot-1

)

Fig.7.8 Effect of different rates of matrix-I formulated calcium carbide with and

without N fertilizer on biological yield of wheat. (Detailed statistical analysis is given in Annexure VII)

0

5

10

15

20

25

30

35

0-0 0-7.5 0-150-22.5 30-0

30-7.530-15

30-22.5 60-060-7.5

60-1560-22.5

Nitrogen-calcium carbide (mg kg-1 soil)

Gra

in y

ield

(g p

ot-1)

Fig.7.9 Effect of different rates of matrix-I formulated calcium carbide with and

without N fertilizer on grain yield of wheat. (Detailed statistical analysis is given in Annexure VII)

Table 7.1 Effect of different rates of matrix-I formulated calcium carbide with and without nitrogen fertilizer on nitrogen concentration and uptake by wheat straw and grain

Rate of N fert. (mg kg-1 soil)

Rate of CaC2 (mg kg-1 soil)

% N in straw % N in grain N uptake by straw (g pot-1)

N uptake by grain (g pot-1)

0 0.37 f 1.55 i 0.06 g 0.22 g 7.5 0.38 f 1.57 i 0.07 fg 0.23 g 15 0.39 e 1.63 h 0.08 fg 0.27 g 0

22.5 0.40 e 1.64 h 0.08 f 0.26 g 0 0.45 d 1.98 g 0.11 e 0.37 f

7.5 0.47 d 2.03 f 0.12 d 0.42 e 15 0.49 c 2.07 e 0.17 b 0.53 cd 30

22.5 0.50 c 2.09 d 0.15 c 0.49 d 0 0.57 b 2.14 c 0.18 b 0.52 d

7.5 0.58 ab 2.18 b 0.22 a 0.62 b 15 0.59 a 2.24 a 0.23 a 0.70 a 60

22.5 0.60 a 2.22 a 0.22 a 0.57 c LSD (p<0.05) 0.014 0.023 0.014 0.045

Figures in the same column with different letter(s) differ significantly at p < 0.05 by LSD test (Detailed statistical analysis is given in Annexure VII)

Table 7.2 Relative percent increase/decrease in growth and yield parameters and nitrogen status of wheat plant due to calcium carbide application compared to respective treatment of fertilizer alone.

Maximum increase due to addition of CaC2 (%)

Parameter No N fert. 1/2 N fert. Full N fert.

Total tillers 14.04 33.33 40.96 Fertile tillers 10.00 42.29 35.71 Plant height -1.38 -4.03 -5.04 Spike length 10.74 8.42 5.26 No. of spikelets /spike 3.71 7.63 6.41 No. of grains /spike 9.23 13.05 9.04 1000-grains weight 6.83 7.26 4.43 Total yield 14.35 42.90 27.29 Grain yield 16.18 36.67 29.72 Straw yield 16.93 47.95 25.43 N %age in grain 5.87 5.56 4.67 N %age in straw 8.11 11.11 5.26 N uptake by grain 22.73 43.24 5.77 N uptake by straw 33.33 54.55 27.78

Table 7.3 Effect of rate of matrix-I formulated calcium carbide with half and full recommended dose of N fertilizer on different efficiency parameters of wheat.

Types of efficiency

N-CaC2 (mg kg-1 soil)

Agronomic Efficiency (g g-1 N)

Physiological Efficiency (g g-1 N)

Apparent N Recovery (%)

30-0 11.6 d 29.5 d 39.2 d 30-7.5 16.5 bc 31.7 bcd 51.7 c 30-15 23.8 a 34.5 ab 68.9 a 30-22.5 20.3 ab 32.6 abcd 61.9 ab 60-0 12.9 cd 32.8 abc 38.9 d 60-7.5 18.4 b 35.4 a 51.9 c 60-15 19.3 b 33.9 abc 56.9 bc 60-22.5 12.8 cd 31.2 cd 40.9 d LSD (p<0.05) 3.9 3.3 7.9

(Detailed statistical analysis is given in Annexure VII)

-------- Inqulab-91-------- ------Bhakhar-2002------

80828486889092949698

100

Matrix-I Matrix-II Paint coated Matrix-I Matrix-II Paint coated

Calcium carbide formulation

Plan

t hei

ght (

cm)

NPK alone NPK + calcium carbide @ 15 kg/ha

NPK + calcium carbide @ 30 kg/ha NPK + calcium carbide @ 45 kg/ha

Average of two years data is presented in this figure

Fig.8.1 Effect of different rates and type of calcium carbide based formulations on plant height of two wheat cultivars under field conditions. (Detailed statistical analysis is given in Annexure VIII) *NPK was applied @ 120, 90 and 60 kg ha-1, respectively.

--------Inqulab-91-------- ------Bhakhar-2002------

100

150

200

250

300

350

400

450

Matrix-I Matrix-II Paint coated Matrix-I Matrix-II Paint coated

Calcium carbide formulation

Num

ber o

f tille

rs m

-2

NPK alone NPK + calcium carbide @ 15 kg/ha

NPK + calcium carbide @ 30 kg/ha NPK + calcium carbide @ 45 kg/ha

Average of two years data is presented in this figure

Fig.8.2 Effect of different rates and type of calcium carbide based formulations on number of tillers of two wheat cultivars under field conditions. (Detailed statistical analysis is given in Annexure VIII) *NPK was applied @ 120, 90 and 60 kg ha-1, respectively.

--------Inqulab-91-------- ------Bhakhar-2002------

150

200

250

300

350

400

Matrix-I Matrix-II Paint coated Matrix-I Matrix-II Paint coated

Calcium carbide formulations

Num

ber o

f spi

kes

m -2

NPK alone NPK + calcium carbide @ 15 kg/ha

NPK + calcium carbide @ 30 kg/ha NPK + calcium carbide @ 45 kg/ha

Average of two years data is presented in this figure

Fig.8.3 Effect of different rates and type of calcium carbide based formulations on number of spikes of two wheat cultivars under field conditions. (Detailed statistical analysis is given in Annexure VIII) *NPK was applied @ 120, 90 and 60 kg ha-1, respectively.

--------Inqulab-91-------- ------Bhakhar-2002------

38

40

42

44

46

48

50

52

Matrix-I Matrix-II Paint coated Matrix-I Matrix-II Paint coated

Calcium carbide formulations

1000

-gra

ins

wei

ght (

g)

NPK alone NPK + calcium carbide @ 15 kg/ha

NPK + calcium carbide @ 30 kg/ha NPK + calcium carbide @ 45 kg/ha

Average of two years data is presented in this figure

Fig.8.4 Effect of different rates and type of calcium carbide based formulations on 1000-grains weight of two wheat cultivars under field conditions. (Detailed statistical analysis is given in Annexure VIII) *NPK was applied @ 120, 90 and 60 kg ha-1, respectively.

--------Inqulab-91-------- ------Bhakhar-2002------

400050006000700080009000

1000011000120001300014000

Matrix-I Matrix-II Paint coated Matrix-I Matrix-II Paint coated

Calcium carbide formulation

Biol

ogic

al y

ield

(kg

ha -1

)NPK alone NPK + calcium carbide @ 15 kg/ha

NPK + calcium carbide @ 30 kg/ha NPK + calcium carbide @ 45 kg/ha

Average of two years data is presented in this figure

Fig.8.5 Effect of different rates and type of calcium carbide based formulations on biological yield of two wheat cultivars under field conditions. (Detailed statistical analysis is given in Annexure VIII) *NPK was applied @ 120, 90 and 60 kg ha-1, respectively.

--------Inqulab-91-------- ------Bhakhar-2002------

1000

2000

3000

4000

5000

6000

7000

Matrix-I Matrix-II Paint coated Matrix-I Matrix-II Paint coated

Calcium carbide formulations

Stra

w y

ield

(kg

ha-1)

NPK alone NPK + calcium carbide @ 15 kg/ha

NPK + calcium carbide @ 30 kg/ha NPK + calcium carbide @ 45 kg/ha

Average of two years data is presented in this figure

Fig.8.6 Effect of different rates and type of calcium carbide based formulations on straw yield of two wheat cultivars under field conditions. (Detailed statistical analysis is given in Annexure VIII) *NPK was applied @ 120, 90 and 60 kg ha-1, respectively.

--------Inqulab-91-------- ------Bhakhar-2002------

1000

2000

3000

4000

5000

6000

7000

Matrix-I Matrix-II Paint coated Matrix-I Matrix-II Paint coated

Calcium carbide formulation

Gra

in y

ield

(kg

ha -1

)NPK alone NPK + calcium carbide @ 15 kg/ha

NPK + calcium carbide @ 30 kg/ha NPK + calcium carbide @ 45 kg/ha

Average of two years data is presented in this figure

Fig.8.7 Effect of different rates and type of calcium carbide based formulations on grain yield of two wheat cultivars under field conditions. (Detailed statistical analysis is given in Annexure VIII) *NPK was applied @ 120, 90 and 60 kg ha-1, respectively.

--------Inqulab-91-------- ------Bhakhar-2002------

0.0

0.5

1.0

1.5

2.0

2.5

Matrix-I Matrix-II Paint coated Matrix-I Matrix-II Paint coated

Calcium carbide formulation

Lodg

ing

inde

x

NPK alone NPK + calcium carbide @ 15 kg/ha

NPK + calcium carbide @ 30 kg/ha NPK + calcium carbide @ 45 kg/ha

Average of two years data is presented in this figure

Fig.8.8 Effect of different rates and type of calcium carbide based formulations on lodging index of two wheat cultivars under field conditions. (Detailed statistical analysis is given in Annexure VIII) *NPK was applied @ 120, 90 and 60 kg ha-1, respectively.

--------Inqulab-91-------- ------Bhakhar-2002------

0.48

0.50

0.52

0.54

0.56

0.58

0.60

Matrix-I Matrix-II Paint coated Matrix-I Matrix-II Paint coated

Calcium carbide formulations

N c

once

ntra

tion

in s

traw

(%

)

NPK alone NPK + calcium carbide @ 15 kg/ha

NPK + calcium carbide @ 30 kg/ha NPK + calcium carbide @ 45 kg/ha

Average of two years data is presented in this figure

Fig.8.9 Effect of different rates and type of calcium carbide based formulations on N concentration in straw of two wheat cultivars under field conditions. (Detailed statistical analysis is given in Annexure VIII) *NPK was applied @ 120, 90 and 60 kg ha-1, respectively.

--------Inqulab-91-------- ------Bhakhar-2002------

1.00

1.20

1.40

1.60

1.80

2.00

2.20

2.40

2.60

Matrix-I Matrix-II Paint coated Matrix-I Matrix-II Paint coated

Calcium carbide formulation

N c

once

ntra

tion

in g

rain

(%)

NPK alone NPK + calcium carbide @ 15 kg/ha

NPK + calcium carbide @ 30 kg/ha NPK + calcium carbide @ 45 kg/ha

Average of two years data is presented in this figure

Fig.8.10 Effect of different rates and type of calcium carbide based formulations on N concentration in grain of two wheat cultivars under field conditions. (Detailed statistical analysis is given in Annexure VIII) *NPK was applied @ 120, 90 and 60 kg ha-1, respectively.

--------Inqulab-91-------- ------Bhakhar-2002------

10

15

20

25

30

35

40

Matrix-I Matrix-II Paint coated Matrix-I Matrix-II Paint coated

Calcium carbide formulations

N u

ptak

e by

stra

w (k

g ha

-1)

NPK alone NPK + calcium carbide @ 15 kg/ha

NPK + calcium carbide @ 30 kg/ha NPK + calcium carbide @ 45 kg/ha

Average of two years data is presented in this figure

Fig.8.11 Effect of different rates and type of calcium carbide based formulations on N uptake by straw of two wheat cultivars under field conditions. (Detailed statistical analysis is given in Annexure VIII) *NPK was applied @ 120, 90 and 60 kg ha-1, respectively.

--------Inqulab-91-------- ------Bhakhar-2002------

20.00

40.00

60.00

80.00

100.00

120.00

140.00

160.00

Matrix-I Matrix-II Paint coated Matrix-I Matrix-II Paint coated

Calcium carbide formulation

N u

ptak

e by

gra

in (k

g ha

-1)

NPK alone NPK + calcium carbide @ 15 kg/ha

NPK + calcium carbide @ 30 kg/ha NPK + calcium carbide @ 45 kg/ha

Average of two years data is presented in this figure

Fig.8.12 Effect of different rates and type of calcium carbide based formulations on N uptake by grain of two wheat cultivars under field conditions. (Detailed statistical analysis is given in Annexure VIII) *NPK was applied @ 120, 90 and 60 kg ha-1, respectively.

aaa

bb

c ccd

e dee

f

0

5

10

15

20

25

30

35

40

Matrix-I Matrix-II Paint coated

Calcium carbide formulation

Soil N

O 3-N

(mg

kg-1 s

oil)

NPK alone NPK + calcium carbide @ 15 kg/ha

NPK + calcium carbide @ 30 kg/ha NPK + calcium carbide @ 45 kg/ha

Average of two years data is presented in this figure

Fig.8.13 Effect of different rates and type of calcium carbide based formulations on soil nitrate-N determined after 8 weeks of CaC2 application under field conditions. (Detailed statistical analysis is given in Annexure VIII)

f f f

d de e

bc c

a

b b

0

5

10

15

20

25

30

35

40

Matrix-I Matrix-II Paint coated

calcium carbide formulation

Soil N

H 4-N

(mg

kg-1 s

oil)

NPK alone NPK + calcium carbide @ 15 kg/ha

NPK + calcium carbide @ 30 kg/ha NPK + calcium carbide @ 45 kg/ha

Average of two years data is presented in this figure Fig.8.14 Effect of different rates and type of calcium carbide based formulations

on soil ammonium-N determined after 8 weeks of CaC2 application under field conditions. (Detailed statistical analysis is given in Annexure VIII) *NPK was applied @ 120, 90 and 60 kg ha-1, respectively

Table 8.1 Lodging response of two wheat cultivars to applied calcium carbide.

0.2* V1F1C1

0.2 V1F2C2

0.4 V1F3C1

0.2 V2F3C4

0.2 V2F2C3

3.8 V2F1C1

0.2 V1F2C1

0.2 V1F3C4

0.2 V1F1C1

0.2 V1F1C4

0.2 V1F2C4

0.4 V1F3C3

0.2 V2F3C3

0.2 V2F2C2

0.2 V2F1C2

0.2 V1F2C3

0.4 V1F3C1

0.2 V1F1C3

0.2 V1F1C3

0.2 V1F2C3

0.2 V1F3C2

0.2 V2F3C2

0.2 V2F2C4

0.2 V2F1C3

0.2 V1F2C2

0.2 V1F3C3

0.2 V1F1C2

0.2 V1F1C2

0.2 V1F2C1

0.2 V1F3C4

4.8 V2F3C1

3.2 V2F2C1

0.2 V2F1C4

0.2 V1F2C4

0.2 V1F3C2

0.2 V1F1C4

0.4 V2F1C2

0.2 V2F3C4

4.8 V2F2C1

0.2 V1F1C1

0.2 V1F3C4

0.2 V1F2C1

0.2 V2F2C3

0.2 V2F1C4

4.6 V2F3C1

0.2 V2F1C3

0.2 V2F3C2

0.4 V2F2C3

0.2 V1F1C3

0.2 V1F3C1

0.2 V1F2C2

0.2 V2F2C2

0.2 V2F1C1

0.2 V2F3C2

2.8 V2F1C1

0.2 V2F3C3

0.2 V2F2C2

0.2 V1F1C2

0.4 V1F3C3

0.2 V1F2C3

5.2 V2F2C1

0.6 V2F1C3

0.2 V2F3C3

0.4 V2F1C4

5.2 V2F3C1

0.2 V2F2C4

0.2 V1F1C4

0.4 V1F3C2

0.4 V1F2C4

0.4 V2F2C4

0.2 2F1C2

5.8 V2F3C4

* Lodging Index V1= c.v. Inqulab-91; V2= c.v. Bhakhar-2002. F1= matrix-I; F2= matrix-II; F3= paint coated CaC2. C1, C2, C3 and C4 = Calcium carbide @ 0, 15, 30 and 45 kg ha-1, respectively.

145

CHAPTER 5 SUMMARY

Soils of the Pakistan are deficient in nitrogen (N) mainly because applied N

fertilizers are immediately undergone transformations such as volatilization, nitrification,

denitrification and leaching. That is why every time nitrogenous fertilizers are applied

widely to fulfill the demand of crop plants and it is recommended to apply N fertilizers

particularly in splits to make availability of nitrogen at critical stages of crop. Most of the

N fertilizers are applied in the form of ammonical compounds and under arid and semi

arid conditions, a big part of the surface applied N is lost by ammonia volatilization

(more than 35%). Thus N use efficiency seldom exceeds 40 %. Incorporation or deep

placement of N fertilizer into the soil is a recommended practice to check or reduce N

losses via ammonia volatilization. However, these methods of N fertilizer application

increase the contact of N with the soil that ultimately boost up the nitrification process

which is a major N transformation process in the soils of arid and semi arid regions.

Nitrification is a two step biochemical process that involves oxidation of ammonium to

nitrite and then nitrite to nitrate in the presence of Nitrosomonas and Nitrobactor species

of bacteria, respectively. Nitrate formed during nitrification process may loss via

denitrification or leaching. Thus it seems rational to enhance N use efficiency by

adopting some improved fertilizer and crop practices or to inhibit nitrification process by

the use of some nitrification inhibitor.

A number of chemicals were tested to inhibit nitrification but most of them had

limited use and thus rejected due to specific condition for their use and cost. Acetylene is

recognized as a nitrification inhibitor gas. However, being gas, it is difficult to use in the

agriculture systems. So a number of acetylene releasing compounds have been tested in

the soil environment for their nitrification inhibition property. Calcium carbide (CaC2) is

considered as the best and effective source of acetylene in the soil by most of the research

workers mainly because it is easily available and economical to use. Calcium carbide

reacts with water to produce acetylene in situ in the soil but this reaction is very fast and

acetylene releases too rapidly that may damage rather than benefit crop production. To

slow down the reaction of calcium carbide with water it is usually coated with some

146

hydrophobic materials. A number of research workers confirmed the effectiveness of

coated calcium carbide as a nitrification inhibitor in different types of cropping systems.

Most recent and effective calcium carbide based formulations are prepared by using

polyethylene and such formulations are called matrices. These matrices proved reliable

source of acetylene than wax coated calcium carbide.

Acetylene releases from CaC2 in the soil environment is reduced to plant hormone

‘ethylene’ by indigenous soil microbes. Ethylene is a plant growth regulator and

influences a number of plant growth and developmental processes from seed germination

to senescence. Russian scientists developed a new ethylene producer in the soil under the

trade name of “Retprol”. Retprol is a calcium carbide based formulation that slowly

breaks down to release acetylene upon interaction with soil water. This acetylene is

readily reducible to ethylene by soil indigenous microbes. It was reported that ethylene

production from soil applied calcium carbide (Retprol) improved economical yield of

crop plants upto 70%. Response of cereals growth and development to exogenously

supplied ethylene was also studied by the application of an ethylene releasing compound

ethephon. It is reported that ethephon spray effectively reduced plant height, strengthen

stem, enhanced total as well as spike bearing tillers, reduced lodging and ultimately

improved economical yield.

Keeping in view the role of calcium carbide in plant growth and developmental

processes, it was considered to explore its potential in the soil environment of Pakistan. It

was an innovative activity in the country to enhance crop yield by combination of

conventional and non conventional approaches. It was also considered necessary to know

right rate, time and coating material as well as appropriate depth of application of

calcium carbide. These factors surely improve effectiveness of applied calcium carbide.

A series of laboratory, wire house and field trials were conducted to evaluate the above

factors to improve growth and yield of wheat.

To find out right rate and time of application of calcium carbide for improving

growth and yield of wheat, calcium carbide was applied from zero to 37.5 mg kg-1 soil

with an incremental dose of 7.5 mg kg-1 soil. These rates were applied 4 cm deep in soil.

Encapsulation in gelatin capsules was done just to safely place the powdered CaC2 at

required depth. Results revealed that application of encapsulated calcium carbide (ECC)

147

@ 22.5 mg kg-1 soil performed the best regarding growth and yield parameters like

number of tillers, root weight, straw yield, grain yield and N uptake by wheat plants

compared to all other rates of CaC2 application. Encapsulated calcium carbide @ 22.5 mg

kg-1 soil applied in combination with NPK fertilizers increased number of tillers, grain

yield and N uptake of wheat by 24, 22 and 21 %, respectively compared to that of alone

NPK fertilizers.

The best rate i.e. 22.5 mg kg-1 soil selected from the 1st experiment was applied at

three times i.e. at sowing, 2 and 4 weeks after sowing of wheat seeds. The results

revealed that application of ECC two weeks after sowing was found better. That might be

due to the reason that at 2 weeks after sowing, plants have already developed some root

system to better absorb ethylene and nutrients.

Since literature revealed that slow and consistent release of acetylene from

applied CaC2 could give better control on nitrification process and thus leads to prolong

the stay of available form of nitrogen. To develop this property, calcium carbide grains of

2-4 mm diameter were coated with bee wax, paraffin wax, black enamel paint and

polyethylene matrices. Encapsulated and coated calcium carbide was compared with

matrix-I (21 % CaC2), matrix-II (42 % CaC2) and matrix-III (61 % CaC2) regarding

acetylene and ethylene release in the soil environment under laboratory conditions. It was

observed that application of 22.5 mg kg-1 soil CaC2 in matrix-I formulation released more

persistent supply of acetylene and ethylene gases for longer period compared to all other

type of coatings. These results were further confirmed by conducting another experiment

where better control on nitrification process was obtained by the application of matrix-I

formulation. Presence of high concentration of NH4+-N than NO3

--N after 8 weeks of

application of coated CaC2 confirmed that nitrification was successfully inhibited by the

applied calcium carbide.

In further experimentation, all seven calcium carbide based formulations were

further compared regarding seed germination, seedling emergence and growth and yield

parameters of wheat. Calcium carbide application in the form of matrix-I formulation

reduced mean emergence time of wheat seedlings and plant height; improved total as

well as spike bearing tillers; enhanced straw and grain yield and N uptake by different

plant parts in a better way than other calcium carbide formulations.

148

Results of above experiments revealed that matrix-I was found as the best among

all the seven calcium carbide based formulations and it was used in further

experimentation to know its appropriate rate and application depth regarding its effect on

wheat growth and yield parameters and N economy of the soil crop. Matrix-I was applied

@ 0, 7.5, 15 and 22.5 mg CaC2 kg-1 soil at 0, 4, 8 and 12 cm soil depth. Maximum grain

yield and positive effect on other growth and yield contributing parameters were

observed where matrix-I formulation @ 15 mg CaC2 kg-1 soil was applied at 8 cm depth

compared to its other rates and application depths.

To check the beneficial effects of nitrification inhibition with calcium carbide

application on nitrogen use efficiency and yield of wheat crop, different rates of matrix-I

formulation was applied with zero, half and full recommended dose of nitrogen fertilizer.

Although, maximum level of growth and yield parameters of wheat were observed in the

treatment where matrix-I was applied @ 15 mg CaC2 with full recommended dose of N

fertilizer. However, calcium carbide application gave more marginal benefit when

applied with half recommended dose of N fertilizer than with full dose of it. Application

of matrix-I formulation enhanced agronomic efficiency, physiological efficiency and

apparent N recovery upto 30, 36 and 82 %, respectively when applied in combination

with half of the recommended dose of N fertilizer compared to half dose of nitrogen

fertilizer alone.

The results obtained from laboratory and wirehouse trials were confirmed by

conducting field trials in two consecutive years on farmer’s field. Besides effect of

calcium carbide on growth and yield of wheat, the objective of these field trials was also

to observe the role of CaC2 on lodging of tall wheat cultivars. Therefore two wheat

cultivars Inqulab-91 (lodging resistant) and Bhakhar-2002 (lodging susceptible) were

included in these trials. Calcium carbide as matrix-I, matrix-II and paint coated calcium

carbide was applied @ 0, 15, 30 and 45 kg ha-1 two weeks after sowing at 8 cm depth. All

plant growth and yield contributing parameters were significantly affected by calcium

carbide almost in a similar fashion as in case of pot experiments. About 28 % increase in

grain yield was observed under field conditions where calcium carbide was applied @ 30

kg ha-1 in matrix-I formulation. Crop lodging was observed only in the 2nd year in

Bhakhar-2002 plots where no calcium carbide was applied. Under field conditions

149

calcium carbide application effectively inhibits nitrification process and delayed the

conversion of ammonium-N to nitrate-N as more ammonium and less nitrate

concentration was observed in the treatments of calcium carbide application than those

without it.

Concluding Remarks Overall results of these experiments indicate that calcium carbide is a good source

of acetylene and ethylene in the soil environment. It effectively inhibits nitrification

process and improves the grain yield of wheat by improving growth and yield parameters

and nitrogen use efficiency of the crop. Regarding wheat plant growth and yield

improvement and nitrification inhibition, matrix-I @ 30 kg ha-1 CaC2 is a better

formulation of calcium carbide when it is applied 2 weeks after sowing at 8 cm soil

depth.

Future Directions It will be more knowledge oriented if both the aspects of calcium carbide

application (nitrification inhibition and ethylene production) be studied separately by

using ethylene synthesis and action inhibitor for all the calcium carbide based

formulations described in this manuscript.

Due to favorable soil and environmental conditions in the field experiment, only

minor lodging of the crop was observed and due to the same reason this aspect is still

demanding more research. On the same pattern experiments may be conducted for crops

other than wheat. It is also the demand of results that acetylene and ethylene evolving

from the soil surface amended with calcium carbide under field conditions be determined.

So that gas flux and plant growth changes be better correlated.

150

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Abeles, F.B. and J. Lonski. 1969. Stimulation of lettuce seed germination by ethylene.

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Abeles, F.B., P.W. Morgan, M.E. Salt and Jr. Veit. 1992. Ethylene in Plant Biology, 2nd

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Ahmad, Z., F. Azam, T. Mahmood, M. Arshad and S. Nadeem. 2004. Use of plant growth

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Arnon, I. 1972. Plant population and distribution patterns in crop production in dry regions.

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Arshad, M. and W.T Frankenberger Jr. 1990. Ethylene accumulation in soil in response to

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Arshad, M. and W.T. Frankenberger Jr. 1988. Influence of ethylene produced by soil

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Arshad, M. and W.T. Frankenberger Jr. 2002. Ethylene: Agricultural Sources and

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Aulakh, M.S., D.A. Rennie and E.A. Paul. 1984. Acetylene and N-serve effects upon N2O

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Aulakh, M.S., J.W. Doran and A.R. Mosier. 1992. Soil denitrification-significance,

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167

ANNEXURE I

Effect of Rate of Encapsulated Calcium Carbide on Growth, Yield and

Nitrogen Uptake of Wheat (Pot Trial)

Treatment Plant height

Number of tillers

Root weight

Straw yield

Grain yield

Average nitrogen conc. by wheat tops (%)

Nitrogen uptake

by wheat tops

0-0 70.15 e 11.00 d 5.83 e 17.52 c 14.66 d 0.99 320.1 d 60-0 76.90 a 21.75 c 7.32 d 31.45 b 20.25 c 1.48 764.6 c 60-7.5 75.75 b 22.25 c 7.85 cd 32.25 b 20.97bc 1.46 775.4 c 60-15 73.92bc 24.75 b 8.52 c 34.06 b 22.63bc 1.51 854.1 b 60-22.5 72.50 cd 27.00 a 11.13 a 38.72 a 25.55 a 1.44 926.8 a 60-30 72.32cde 24.75 b 10.73 a 35.56ab 23.36ab 1.50 886.7 ab 60-37.5 70.73 de 24.50 b 9.75 b 33.65 b 22.03bc 1.56 866.3 ab LSD (p<0.05) 2.13 1.76 0.77 4.40 2.76 -- 60.52

Values present average of four replications Plant height

ANALYSIS OF VARIANCE TABLE

K Value

Source Degrees of Freedom

Sum of Squares

Mean Square

F Value

probability

1 Replication 3 19.82 6.61 3.23 0.05 2 Factor A 6 149.60 24.93 12.17 0.00 -3 Error 18 36.86 2.05 Total 27 206.28

Coefficient of Variation 1.96 % Number of tillers pot-1

ANALYSIS OF VARIANCE TABLE

K Value

Source Degrees of Freedom

Sum of Squares

Mean Square

F Value

probability

1 Replication 3 4.86 1.62 1.56 0.35 2 Factor A 6 667.71 111.29 79.67 0.00 -3 Error 18 25.14 1.39 Total 27 697.71

Coefficient of Variation 5.30 %

168

Root weight

ANALYSIS OF VARIANCE TABLE

K Value

Source Degrees of Freedom

Sum of Squares

Mean Square

F Value

probability

1 Replication 3 0.227 0.076 0.29 2 Factor A 6 87.94 14.66 55.53 0.00 -3 Error 18 4.25 0.26 Total 27 92.92

Coefficient of Variation 9.04 % Straw yield

ANALYSIS OF VARIANCE TABLE

K Value

Source Degrees of Freedom

Sum of Squares

Mean Square

F Value

probability

1 Replication 3 17.78 5.93 0.67 2 Factor A 6 1099.68 183.28 20.85 0.00 -3 Error 18 158.19 8.79 Total 27 1275.65

Coefficient of Variation 9.30 %

Grain yield ANALYSIS OF VARIANCE TABLE

K

Value Source Degrees of

Freedom Sum of Squares

Mean Square

F Value

probability

1 Replication 3 17.74 5.91 1.72 0.19 2 Factor A 6 279.39 46.56 13.53 0.00 -3 Error 18 61.96 3.44 Total 27 359.09

Coefficient of Variation 8.69 %

169

Nitrogen uptake ANALYSIS OF VARIANCE TABLE

K

Value Source Degrees of

Freedom Sum of Squares

Mean Square

F Value

probability

1 Replication 3 4467.65 1489.22 0.897 2 Factor A 6 1028289.4 171381.56 103.26 0.00 -3 Error 18 29876.13 1659.78 Total 27 1062633.16

Coefficient of Variation 5.29 %

ANNEXURE II

Effect of Time of Application of Encapsulated Calcium Carbide on

Growth, Yield and Nitrogen Uptake of Wheat (Pot Trial)

Treatment Plant

height Number of tillers

Root weight

Straw yield

Grain yield

Average N conc.

in wheat tops

Nitrogen uptake

T1 70.15 b 12.00 d 5.65 c 19.03 d 14.66 d 0.99 335.6 c T2 76.40 a 20.25 c 7.32 b 31.29 c 20.25 c 1.44 744.6 b T3 72.00 b 24.25 b 9.75 a 35.45 b 23.42 b 1.43 844.2 a T4 69.50 b 27.00 a 9.55 a 40.25 a 26.50 a 1.39 932.3 a T5 72.40 b 22.00 bc 8.08 b 36.68ab 23.98 b 1.47 891.7 a

LSD (p<0.05) 3.717 3.882 0.872 4.06 2.25 -- 88.37

Values present average of four replications Plant height

ANALYSIS OF VARIANCE TABLE

K Value

Source Degrees of Freedom

Sum of Squares

Mean Square

F Value

probability

1 Replication 3 6.19 2.20 0.76 2 Factor A 4 116.61 129.07 44.38 0.00 -3 Error 12 69.86 2.91 Total 19 192.66

Coefficient of Variation 3.35 %

170

Number of tillers pot-1 ANALYSIS OF VARIANCE TABLE

K

Value Source Degrees of

Freedom Sum of Squares

Mean Square

F Value

probability

1 Replication 3 6.6 2.20 0.76 2 Factor A 4 516.30 129.07 44.38 0.00 -3 Error 12 34.90 2.91 Total 19 557.80

Coefficient of Variation 8.08 % Root weight

ANALYSIS OF VARIANCE TABLE

K Value

Source Degrees of Freedom

Sum of Squares

Mean Square

F Value

probability

1 Replication 3 0.95 0.32 0.99 2 Factor A 4 45.99 11.49 36.19 0.00 -3 Error 12 3.81 0.32 Total 19 50.75

Coefficient of Variation 11.06 % Straw yield

ANALYSIS OF VARIANCE TABLE

K Value

Source Degrees of Freedom

Sum of Squares

Mean Square

F Value

probability

1 Replication 3 15.31 5.10 0.74 2 Factor A 4 1076.85 269.21 38.79 0.00 -3 Error 12 83.28 6.94 Total 19 1175.43

Coefficient of Variation 8.10 %

Grain yield ANALYSIS OF VARIANCE TABLE

K

Value Source Degrees of

Freedom Sum of Squares

Mean Square

F Value

probability

1 Replication 3 5.91 1.97 0.93 2 Factor A 4 331.12 82.78 38.88 0.00 -3 Error 12 25.55 2.13 Total 19 362.57

Coefficient of Variation 6.70 %

171

Nitrogen uptake

ANALYSIS OF VARIANCE TABLE

K Value

Source Degrees of Freedom

Sum of Squares

Mean Square

F Value

probability

1 Replication 3 23112.93 7704.3 2.34 0.124 2 Factor A 4 935817.79 233954.4 71.11 0.00 -3 Error 12 39482.86 3290.24 Total 19 998413.59

Coefficient of Variation 7.65 % ANNEXURE III

Evaluation of Different Type of Calcium Carbide Based Formulations

for the Release of Acetylene and Ethylene Gases and Their Effect on

Nitrification Inhibition under Laboratory Conditions Treatments Soil Content

Determi-

nation

time

Type of CaC2

Formulation

Acetylene Ethylene Ammnium-

N

Nitrate-N

Control 0.00 9.67 207.67 24.33

Encapsulated 27587 12.33 206.67 11.00

Bee wax 24722 13.67 207.33 12.66

Paraffin wax 25117 13.00 206.33 9.67

Paint 23260 12.33 208.67 8.67

Matrix-I 22234 13.67 206.33 12.00

Matrix-II 23700 15.00 207.00 11.33

3rd day

after CaC2

application

Matrix-III 26616 13.00 206.33 9.67

Control 0.00 9.33 119.67 74.67

Encapsulated 15352 90.67 191.33 42.00

Bee wax 18817 105.00 184.67 24.33

Paraffin wax 19690 112.67 185.00 28.00

Paint 20666 118.00 187.00 24.67

7th day

after CaC2

application

Matrix-I 20385 152.00 195.67 16.67

172

Matrix-II 18088 128.67 195.33 20.33

Matrix-III 16542 93.67 194.33 48.00

Control 0.00 10.00 12.67 174.00

Encapsulated 7894 140.33 130.66 67.00

Bee wax 13259 197.33 145.67 40.33

Paraffin wax 14809 178.67 149.00 40.00

21st day

after CaC2

application

Paint 17901 197.67 161.00 32.00

Matrix-I 18705 252.67 181.33 20.00

Matrix-II 16422 208.33 175.67 22.33

Matrix-III 6563 139.00 122.00 61.67

Control 0.00 10.67 5.33 181.66

Encapsulated 427 166.67 100.67 89.66

Bee wax 8805 204.33 130.33 50.33

Paraffin wax 7842 213.67 135.67 52.00

Paint 12718 275.00 150.67 46.33

Matrix-I 15483 341.00 163.67 38.00

Matrix-II 13964 308.00 157.00 42.00

35th day after

CaC2

application

Matrix-III 232 176.00 102.67 91.67

Control 0.00 10.33 4.00 171.33

Encapsulated 12.33 1777 79.67 92.66

Bee wax 3656 309.67 119.67 57.33

Paraffin wax 4577 324.67 113.33 56.00

Paint 9484 404.67 120.67 52.33

Matrix-I 12776 466.33 135.66 47.66

Matrix-II 26 445.00 139.67 50.33

49th day after

CaC2

application

Matrix-III 0.00 181.67 77.00 119.33

Control 0.00 10.67 3.00 160.33

Encapsulated 534 145.33 40.67 112.00

Bee wax 672 433.66 92.67 88.33

63rd day after

CaC2

application

Paraffin wax 4711 439.00 80.33 85.00

173

Paint 10418 449.66 78.33 81.00

Matrix-I 7430 531.00 119.66 65.66

Matrix-II 0.00 510.33 111.00 69.67

Matrix-III 0.00 130.00 30.00 137.33

Control 0.00 11.67 2.33 151.33

Encapsulated 0.00 86.00 29.66 117.66

77th day after

CaC2

application Bee wax 80 400.67 70.67 109.33

Paraffin wax 68 395.00 40.67 108.33

Paint 935 403.33 71.67 90.00

Matrix-I 9699 542.67 95.67 88.33

Matrix-II 4471 490.33 86.33 92.66

Matrix-III 0.00 91.67 19.67 157.00

Control 0.00 9.66 1.33 141.00

Encapsulated 0.00 46.00 3.33 143.33

Bee wax 0.00 233.33 16.67 127.33

Paraffin wax 0.00 241.66 21.00 125.33

Paint 56 309.33 30.33 126.00

Matrix-I 4579 448.66 81.00 98.67

Matrix-II 369 344.66 52.00 120.00

91st day after

CaC2

application

Matrix-III 0.00 47.67 7.00 156.00

LSD (p < 0.05) 1239 9.89 3.71 5.91

Acetylene content ANALYSIS OF VARIANCE TABLE

K Value

Source Degrees of Freedom

Sum of Squares Mean Square F Value

probability

2 Time (A) 7 9418643707 1345520529 2286 0.00 4 Formulation (B) 7 3227853070 461121867 783 0.00 6 AB 49 2421656532 49421561 84 0.00 -7 Error 128 75334771 588552 Total 191 15143488081

Coefficient of Variation 9.04 %

174

Ethylene content ANALYSIS OF VARIANCE TABLE

K Value

Source Degrees of Freedom

Sum of Squares

Mean Square

F Value

probability

2 Time (A) 7 1967472 281067 7486 0.00 4 Formulation (B) 7 2221945 317420 8455 0.00 6 AB 49 954930 19488 519 0.00 -7 Error 128 4805 37 Total 191 5149154

Coefficient of Variation 3.02 %

Ammonium-N content

ANALYSIS OF VARIANCE TABLE K Value

Source Degrees of Freedom

Sum of Squares

Mean Square

F Value

probability

2 Time (A) 7 655263 93609 17724 0.00 4 Formulation (B) 7 177689 25384 4806 0.00 6 AB 49 67948 1386 262 0.00 -7 Error 128 676 5 Total 191 901577

Coefficient of Variation 2.07 %

Nitrate-N content

ANALYSIS OF VARIANCE TABLE K Value

Source Degrees of Freedom

Sum of Squares

Mean Square

F Value

probability

2 Time (A) 7 265039 37862 2822 0.00 4 Formulation (B) 7 141994 20284 1511 0.00 6 AB 49 54690 1116 83 0.00 -7 Error 128 1717 13 Total 191 463442

Coefficient of Variation 4.86 %

175

ANNEXURE IV-A

Effect of Calcium Carbide Based Formulations on Seed Germination,

Seedling Growth and Root:Shoot Ratio of Wheat (Laboratory Trial)

Treatment MET ERI FBW-3 FBW-6 FBW-12 FBW-15 T1 5.92 a 2.03 c 96.67 c 114.4 d 141.1 d 90.44 d T2 5.08 b 2.36 bc 103.3 c 121.1 cd 148.9 cd 105.6 c T3 4.50 bc 2.67 ab 101.1 c 124.4 bc 157.8 bc 110.1 bc T4 5.08 ab 2.40 bc 107.8 c 131.1 bc 160.0 bc 110.0 bc T5 5.08 b 2.37 bc 123.3 b 143.1 b 166.7 b 122.0 ab T6 4.08 c 2.96 a 141.1 a 157.8 a 188.9 a 133.3 a T7 4.75 bc 2.53 b 127.8 b 145.6 a 186.7 a 130.7 a T8 5.33 ab 2.27 bc 101.1 c 113.3 cd 148.9 cd 102.9 cd

LSD (p<0.05) 0.765 0.369 11.67 10.50 13.65 12.70

Values present average of three replications

Treatment Root Length

Shoot Length

Root Weight

Shoot Weight

Root/shoot Length

Root/shoot weight

T1 5.23 d 7.00 50.00 e 40.43 0.75 e 1.24 T2 5.61 cd 6.84 59.34 cd 46.23 0.81 de 1.28 T3 6.48 b 6.48 64.22 c 45.90 1.01 bcd 1.43 T4 5.66 cd 6.13 64.45 c 45.57 0.94 bcde 1.54 T5 6.69 b 5.91 74.45 b 47.57 1.14 ab 1.58 T6 7.85 a 6.14 81.00 a 52.30 1.29 a 1.59 T7 6.29 bc 5.81 78.00 ab 52.67 1.09 abc 1.48 T8 5.38 d 6.15 53.33 de 49.57 0.88 cde 1.13

LSD (p<0.05) 0.744 N.S 6.05 N.S 0.218 N.S

Values present average of three replications Mean Emergence Time (MET)

ANALYSIS OF VARIANCE TABLE

K

Value Source Degrees of

Freedom Sum of Squares

Mean Square

F Value

probability

1 Replication 2 0.036 0.018 0.099 2 Factor A 7 6.365 0.909 4.918 0.005 -3 Error 12 2.589 0.185 Total 23 8.990

Coefficient of Variation 8.64 %

176

Emergence Rate Index (ERI) ANALYSIS OF VARIANCE TABLE

K

Value Source Degrees of

Freedom Sum of Squares

Mean Square

F Value

probability

1 Replication 2 0.019 0.010 0.222 2 Factor A 7 1.605 0.229 5.503 0.003 -3 Error 12 0.605 0.043 . Total 23 2.230

Coefficient of Variation 8.49 %

Fresh biomass weight after 3 days of sowing (FBW-3)

ANALYSIS OF VARIANCE TABLE

K Value

Source Degrees of Freedom

Sum of Squares

Mean Square

F Value

probability

1 Replication 2 100.98 50.49 1.173 0.34 2 Factor A 7 5355.27 765.04 17.77 0.00 -3 Error 12 602.83 43.06 Total 23 6059.07

Coefficient of Variation 5.82 % Fresh biomass weight 6 days after sowing (FBW-6)

ANALYSIS OF VARIANCE TABLE

K

Value Source Degrees of

Freedom Sum of Squares

Mean Square

F Value

probability

1 Replication 2 45.42 22.71 0.652 2 Factor A 7 5419.81 774.26 22.21 0.00 -3 Error 12 487.96 34.85 Total 23 5953.19

Coefficient of Variation 4.49 % Fresh biomass weight 12 days after sowing (FBW-12)

ANALYSIS OF VARIANCE TABLE

K Value

Source Degrees of Freedom

Sum of Squares

Mean Square

F Value

probability

1 Replication 2 34.24 17.12 0.291 2 Factor A 7 6463.21 923.32 15.673 0.00 -3 Error 12 824.74 58.91 Total 23 7322.19

Coefficient of Variation 4.73 %

177

Fresh biomass weight 15 days after sowing (FBW-15)

ANALYSIS OF VARIANCE TABLE

K Value

Source Degrees of Freedom

Sum of Squares

Mean Square

F Value

probability

1 Replication 2 109.23 54.614 1.072 0.37 2 Factor A 7 4470.63 638.66 12.54 0.00 -3 Error 12 713.17 50.94 Total 23 5293.034

Coefficient of Variation 6.31 % Root Length

ANALYSIS OF VARIANCE TABLE

K Value

Source Degrees of Freedom

Sum of Squares

Mean Square

F Value

probability

1 Replication 2 1.223 0.612 3.496 0.058 2 Factor A 7 15.81 2.258 12.907 0.00 -3 Error 12 2.450 0.175 Total 23 19.478

Coefficient of Variation 6.80 % Shoot Length

ANALYSIS OF VARIANCE TABLE

K Value

Source Degrees of Freedom

Sum of Squares

Mean Square

F Value

probability

1 Replication 2 0.230 0.115 0.199 2 Factor A 7 4.039 0.557 0.997 -3 Error 12 8.101 0.579 Total 23 12.370

Coefficient of Variation 12.05 % Root Weight

ANALYSIS OF VARIANCE TABLE

K Value

Source Degrees of Freedom

Sum of Squares

Mean Square

F Value

probability

1 Replication 2 72.26 36.13 3.13 0.075 2 Factor A 7 2716.72 388.1 33.58 0.00 -3 Error 12 161.79 11.56 Total 23 2950.79

Coefficient of Variation 5.18 %

178

Shoot Weight

ANALYSIS OF VARIANCE TABLE

K Value

Source Degrees of Freedom

Sum of Squares

Mean Square

F Value

probability

1 Replication 2 10.56 5.28 0.073 2 Factor A 7 335.53 47.93 0.663 -3 Error 12 1011.937 72.28 Total 23 1358.03

Coefficient of Variation 17.89 % Root:Shoot Ratio by Length

ANALYSIS OF VARIANCE TABLE

K Value

Source Degrees of Freedom

Sum of Squares

Mean Square

F Value

probability

1 Replication 2 0.036 0.018 1.173 0.338 2 Factor A 7 0.673 0.096 6.324 0.002 -3 Error 12 0.213 0.015 Total 23 0.921

Coefficient of Variation 12.47 % Root:Shoot Ratio by weight

ANALYSIS OF VARIANCE TABLE

K

Value Source Degrees of

Freedom Sum of Squares

Mean Square

F Value

probability

1 Replication 2 0.037 0.019 0.175 2 Factor A 7 0.622 0.089 0.833 -3 Error 12 1.490 0.107 Total 23 2.150

Coefficient of Variation 23.18 %

179

ANNEXURE IV-B

Effect of Different Doses of Matrix-I Based Calcium Carbide on Wheat Seedling Emergence (Pot Trial)

Rate of CaC2 Mean emergence time Emergence rate index

0 5.28 a 2.28 d 7.5 4.64 b 2.59 c 15 4.00 d 3.00 a 30 4.31 c 2.79 b

LSD (p<0.05) 0.268 0.167 Values present average of three replications Mean Emergence Time (MET)

ANALYSIS OF VARIANCE TABLE

K

Value Source Degrees of

Freedom Sum of Squares

Mean Square

F Value

probability

1 Replication 2 0.072 0.036 1.989 0.217 2 Factor A 3 2.706 0.902 49.53 0.0001 -3 Error 6 0.109 0.018 Total 11 2.888

Coefficient of Variation 2.96 % Emergence Rate Index (ERI)

ANALYSIS OF VARIANCE TABLE

K

Value Source Degrees of

Freedom Sum of Squares

Mean Square

F Value

probability

1 Replication 2 0.021 0.010 1.4196 0.313 2 Factor A 3 0.855 0.285 39.297 0.0002 -3 Error 6 0.044 0.007 Total 11 0.92

Coefficient of Variation 3.20 %

180

ANNEXURE V

Effect of Calcium Carbide Based Formulations on Growth, Yield and

Nitrogen Uptake of Wheat (Pot Trial)

Treatment Plant height

Total tillers

Fertile tillers

1000-grains weight

Root Weight

Biological yield

T1 69.30 d 15.67 g 10.33 e 41.78 c 3.68 f 31.50 g T2 81.83 a 24.33 f 17.00 d 46.71 b 8.22 e 48.50 f T3 78.87 b 26.00 ef 21.67 c 47.13 b 9.71 c 57.66 de T4 76.00 bc 27.67 de 23.00 bc 48.08 ab 9.56 cd 60.10 d T5 76.50 bc 28.67 cd 23.00 bc 48.11 ab 9.79 c 60.03 d T6 76.67 bc 30.33 bc 25.00 ab 48.89 a 10.72 b 63.88 c T7 75.33 c 32.33 a 27.00 a 49.42 a 11.62 a 70.91 a T8 75.00 c 31.67 ab 26.00 a 49.30 a 10.84 b 66.73 b T9 77.00 bc 27.67 de 23.00 bc 47.12 b 8.85 de 56.66 e

LSD (p<0.05) 2.65 1.86 2.01 1.30 0.71 2.66

Values present average of three replications

Treatment Grain yield

N conc. in root

N conc. In straw

N conc. in grain

N uptake by root

N uptake by straw

T1 14.74 g 0.287 e 0.36 e 1.58 d 10.60 f 60.27 e T2 21.39 f 0.453 d 0.56 d 2.13 c 37.30 e 152.5 d T3 25.11 e 0.463 cd 0.57 cd 2.16 c 44.97 c 186.5 bc T4 27.24 cd 0.466 cd 0.58 bc 2.21 b 44.63 cd 191.7 bc T5 27.55 c 0.466 cd 0.58 bc 2.25 a 45.70 c 189.5 bc T6 29.50 b 0.477 bc 0.59 ab 2.24 ab 51.10 b 203.0 b T7 31.87 a 0.487 ab 0.60 a 2.27 a 56.57 a 224.5 a T8 29.54 b 0.493 a 0.59 ab 2.26 a 53.50 ab 231.6 a T9 25.52 de 0.467 cd 0.57 cd 2.15 c 41.33 d 178.5 c

LSD (p<0.05) 1.86 0.013 0.013 0.03 3.37 6.99

Values present average of three replications

181

Treatment N uptake by

grain Nitrate-N Ammonium-N

T1 232.9 g 4.47 f 3.36 g T2 455.8 f 36.23 a 17.93 f T3 541.8 e 23.26 b 30.10 e T4 601.8 d 18.49 c 36.99 c T5 619.9 cd 17.39 c 38.93 b T6 659.8 bc 17.21 c 39.93 b T7 722.5 a 12.22 e 48.21 a T8 668.5 b 13.72 d 46.76 a T9 549.7 e 22.87 b 32.59 d

LSD (p<0.05) 43.59 1.36 1.78 Values present average of three replications Plant height

ANALYSIS OF VARIANCE TABLE

K Value

Source Degrees of Freedom

Sum of Squares

Mean Square

F Value

probability

1 Replication 2 2.276 1.34 0.48 2 Factor A 8 268.74 33.59 14.27 0.00 -3 Error 16 7.65 2.35 Total 26 308.67

Coefficient of Variation 2.01 % Total number of tillers pot-1

ANALYSIS OF VARIANCE TABLE

K Value

Source Degrees of Freedom

Sum of Squares

Mean Square

F Value

probability

1 Replication 2 0.96 0.48 0.42 2 Factor A 8 604.074 75.51 65.76 0.00 -3 Error 16 18.37 1.148 Total 26 623.41

Coefficient of Variation 3.95 %

182

Number of fertile tillers pot-1

ANALYSIS OF VARIANCE TABLE

K Value

Source Degrees of Freedom

Sum of Squares

Mean Square

F Value

probability

1 Replication 2 1.556 0.78 0.57 2 Factor A 8 641.33 80.17 58.898 0.00 -3 Error 16 21.78 1.36 Total 26 664.67

Coefficient of Variation 5.36 % 1000-grains weight

ANALYSIS OF VARIANCE TABLE

K Value

Source Degrees of Freedom

Sum of Squares

Mean Square

F Value

probability

1 Replication 2 1.49 0.74 1.337 0.29 2 Factor A 8 129.25 16.16 29.05 0.00 -3 Error 16 8.89 0.56 Total 26 139.63

Coefficient of Variation 1.57 % Root weight

ANALYSIS OF VARIANCE TABLE

K Value

Source Degrees of Freedom

Sum of Squares

Mean Square

F Value

probability

1 Replication 2 0.037 0.018 0.106 2 Factor A 8 129.302 16.16 92.92 0.00 -3 Error 16 2.78 0.174 Total 26 132.12

Coefficient of Variation 4.52 % Biological yield

ANALYSIS OF VARIANCE TABLE

K Value

Source Degrees of Freedom

Sum of Squares

Mean Square

F Value

probability

1 Replication 2 4.12 2.06 0.87 2 Factor A 8 3229.08 403.64 171.04 0.00 -3 Error 16 37.75 2.36 Total 26 3270.95

Coefficient of Variation 2.68 %

183

Grain yield ANALYSIS OF VARIANCE TABLE

K

Value Source Degrees of

Freedom Sum of Squares

Mean Square

F Value

probability

1 Replication 2 3.63 1.81 1.56 0.24 2 Factor A 8 636.00 79.50 68.63 0.00 -3 Error 16 18.53 1.16 Total 26 658.16

Coefficient of Variation 4.17 % N concentration in grain

ANALYSIS OF VARIANCE TABLE

K Value

Source Degrees of Freedom

Sum of Squares

Mean Square

F Value

probability

1 Replication 2 1.001 0.00005 1.21 0.32 2 Factor A 8 1.115 0.136 418.78 0.00 -3 Error 16 0.005 0.000063 Total 26 1.121

Coefficient of Variation 0.85 % N concentration in straw

ANALYSIS OF VARIANCE TABLE

K Value

Source Degrees of Freedom

Sum of Squares

Mean Square

F Value

probability

1 Replication 2 0.0001 0.00005 1.32 0.295 2 Factor A 8 0.136 0.136 215.91 0.00 -3 Error 16 0.001 0.000063 Total 26 0.137

Coefficient of Variation 1.59 % N concentration in root

ANALYSIS OF VARIANCE TABLE

K

Value Source Degrees of

Freedom Sum of Squares

Mean Square

F Value

probability

1 Replication 2 0.0001 0.00005 0.182 2 Factor A 8 0.095 0.012 194.04 0.00 -3 Error 16 0.001 0.0005 Total 26 0.096

Coefficient of Variation 1.73 %

184

N uptake by grain ANALYSIS OF VARIANCE TABLE

K

Value Source Degrees of

Freedom Sum of Squares

Mean Square

F Value

probability

1 Replication 2 2157.55 1078.77 1.70 0.214 2 Factor A 8 515132.17 64391.52 101.54 0.000 -3 Error 16 10146.29 634.14 Total 26 527436.02

Coefficient of Variation 4.49 % N uptake by straw

ANALYSIS OF VARIANCE TABLE

K Value

Source Degrees of Freedom

Sum of Squares

Mean Square

F Value

probability

1 Replication 2 278.014 139.0 0.94 2 Factor A 8 61614.69 7701.8 52.40 0.00 -3 Error 16 2351.57 146.97 Total 26 64244.27

Coefficient of Variation 6.74 % N uptake by root

ANALYSIS OF VARIANCE TABLE

K Value

Source Degrees of Freedom

Sum of Squares

Mean Square

F Value

probability

1 Replication 2 1.22 0.61 0.16 2 Factor A 8 4375.7 546.97 144.05 0.00 -3 Error 16 60.75 3.79 Total 26 4437.71

Coefficient of Variation 4.55 % Nitrate-N

ANALYSIS OF VARIANCE TABLE

K Value

Source Degrees of Freedom

Sum of Squares

Mean Square

F Value

probability

1 Replication 2 1.48 0.74 1.199 0.327 2 Factor A 8 1854.30 231.79 375.23 0.00 -3 Error 16 9.88 0.62 Total 26 1865.67

Coefficient of Variation 4.27 %

185

Ammonium-N ANALYSIS OF VARIANCE TABLE

K

Value Source Degrees of

Freedom Sum of Squares

Mean Square

F Value

probability

1 Replication 2 4.77 2.38 2.26 0.136 2 Factor A 8 4900.37 612.55 580.16 0.00 -3 Error 16 16.89 1.056 Total 26 4922.04

Coefficient of Variation 3.14 %

186

ANNEXURE VI

Effect of Rate and Application Depth of Matrix-I Calcium Carbide

Based Formulation on Growth, Yield and N uptake of Wheat (Pot Trial)

Plant height

ANALYSIS OF VARIANCE TABLE

K Value

Source Degrees of Freedom

Sum of Squares

Mean Square

F Value

probability

2 Depth (A) 3 45.62 15.21 24.28 0.00 4 Rate (B) 3 68.31 22.77 36.36 0.00 6 AB 9 22.65 2.52 4.02 0.00 -7 Error 48 30.06 0.63 Total 63 166.64

Coefficient of Variation 0.78 % Total number of tiller pot-1

ANALYSIS OF VARIANCE TABLE

K

Value Source Degrees of

Freedom Sum of Squares

Mean Square

F Value

probability

2 Depth (A) 3 375.62 125.21 58.35 0.00 4 Rate (B) 3 258.62 86.21 40.17 0.00 6 AB 9 92.50 10.28 4.79 0.00 -7 Error 48 103.00 2.15 Total 63 829.75

Coefficient of Variation 5.96 % Number of fertile tillers pot-1

ANALYSIS OF VARIANCE TABLE

K

Value Source Degrees of

Freedom Sum of Squares

Mean Square

F Value

probability

2 Depth (A) 3 212.67 70.89 42.67 0.00 4 Rate (B) 3 99.55 33.18 19.97 0.00 6 AB 9 62.27 6.92 4.16 0.00 -7 Error 48 79.75 1.66 Total 63 254.23

Coefficient of Variation 6.75 %

187

Number of unfertile tillers pot-1

ANALYSIS OF VARIANCE TABLE

K Value

Source Degrees of Freedom

Sum of Squares

Mean Square

F Value

probability

2 Depth (A) 3 157.17 52.39 17.37 0.00 4 Rate (B) 3 90.55 30.18 10.00 0.00 6 AB 9 111.39 12.38 4.10 0.00 -7 Error 48 144.75 3.02 Total 63 503.86

Coefficient of Variation 31.86 % 1000-grains weight

ANALYSIS OF VARIANCE TABLE

K

Value Source Degrees of

Freedom Sum of Squares

Mean Square

F Value

probability

2 Depth (A) 3 27.8 9.27 17.05 0.00 4 Rate (B) 3 29.22 9.74 17.92 0.00 6 AB 9 35.41 3.93 7.24 0.00 -7 Error 48 26.09 0.54 Total 63 118.51

Coefficient of Variation 1.58 % Biological yield

ANALYSIS OF VARIANCE TABLE

K

Value Source Degrees of

Freedom Sum of Squares

Mean Square

F Value

probability

2 Depth (A) 3 4060.35 1353.45 107.51 0.00 4 Rate (B) 3 2718.79 906.27 71.99 0.00 6 AB 9 1944.77 216.09 17.16 0.00 -7 Error 48 604.28 12.59 Total 63 9328.2

Coefficient of Variation 5.78 %

188

Grain yield

ANALYSIS OF VARIANCE TABLE

K Value

Source Degrees of Freedom

Sum of Squares

Mean Square

F Value

probability

2 Depth (A) 3 615.58 205.19 118.18 0.00 4 Rate (B) 3 488.43 163.14 93.96 0.00 6 AB 9 343.79 38.19 92.00 0.00 -7 Error 48 83.34 1.74 Total 63 1532.14

Coefficient of Variation 4.88 % Nitrogen concentration in wheat grains

ANALYSIS OF VARIANCE TABLE

K

Value Source Degrees of

Freedom Sum of Squares

Mean Square

F Value

probability

2 Depth (A) 3 0.099 0.033 120.13 0.00 4 Rate (B) 3 0.141 0.047 171.08 0.00 6 AB 9 0.052 0.006 21.07 0.00 -7 Error 48 0.013 0.00027 Total 63 0.304

Coefficient of Variation 0.76 % Nitrogen concentration in wheat straw

ANALYSIS OF VARIANCE TABLE

K Value

Source Degrees of Freedom

Sum of Squares

Mean Square

F Value

probability

2 Depth (A) 3 0.014 0.005 39.81 0.00 4 Rate (B) 3 0.016 0.005 45.36 0.00 6 AB 9 0.008 0.001 7.69 0.00 -7 Error 48 0.006 0.0001 Total 63 0.043

Coefficient of Variation 1.96 %

189

Nitrogen uptake by wheat grains

ANALYSIS OF VARIANCE TABLE

K

Value Source Degrees of

Freedom Sum of Squares

Mean Square

F Value

probability

2 Depth (A) 3 0.41 0.137 206.84 0.00 4 Rate (B) 3 0.36 0.122 184.43 0.00 6 AB 9 0.17 0.018 27.85 0.00 -7 Error 48 0.032 0.0006 Total 63 0.979

Coefficient of Variation 4.36 % Nitrogen uptake by wheat straw

ANALYSIS OF VARIANCE TABLE

K

Value Source Degrees of

Freedom Sum of Squares

Mean Square

F Value

probability

2 Depth (A) 3 0.062 0.021 68.83 0.00 4 Rate (B) 3 0.043 0.014 48.14 0.00 6 AB 9 0.028 0.003 10.57 0.00 -7 Error 48 0.014 0.0002 Total 63 0.147

Coefficient of Variation 9.08 %

190

ANNEXURE VII

Response of Wheat to Soil Applied Matrix-I Formulated Calcium

Carbide with and without Nitrogen Fertilizer (Pot Trial)

N-CaC2 (mg kg-1)

Plant height

Total number of

tillers

Number of fertile tillers

Spike length

Number of spikelets per spike

0-0 75.29 g 14.25 h 10.00 e 8.29 e 11.57 e 0-7.5 75.17 gh 14.75 gh 10.50 e 8.55 e 11.61 e 0-15 74.54 gh 15.50 fgh 11.00 e 9.18 d 11.96 e 0-22.5 73.93 h 16.25 fg 10.25 e 9.15 d 12.01 e 30-0 85.18 d 17.25 f 14.00 d 9.03 d 14.14 d 30-7.5 83.36 e 20.50 e 16.67 c 9.79 c 15.02 d 30-15 82.26 ef 23.00 d 19.91 b 9.78 c 15.23 d 30-22.5 81.74 f 22.75 d 17.75 c 9.76 c 14.94 c 60-0 94.27 a 20.75 e 17.50 c 10.26 b 16.70 b 60-7.5 91.92 b 24.75 c 20.00 b 10.48 ab 17.42 ab 60-15 90.73 b 26.75 b 23.75 a 10.80 a 17.77 a 60-22.5 89.52 c 29.25 a 22.50 a 10.39 ab 16.91 b

LSD (p<0.05) 1.19 1.67 1.72 0.42 0.79 Values are averages of four replications

N-CaC2 (mg kg-1)

Number of grains per

spike

1000-grains weight

Biological yield

Grain yield

0-0 44.32 g 41.12 f 31.99 i 14.39 h 0-7.5 45.31 fg 42.56 e 32.44 i 14.53 h 0-15 47.68 def 43.94 e 36.33 h 16.73 g 0-22.5 48.42 cde 43.56 e 36.57 h 16.00 gh 30-0 47.21 ef 45.75 d 41.96 g 18.76 f 30-7.5 49.41 cde 47.50 c 46.55 f 20.73 e 30-15 53.37 a 49.06 ab 59.95 d 25.64 c 30-22.5 50.62 bc 46.92 cd 54.69 e 23.62 d 60-0 50.02 cd 48.36 bc 55.44 e 24.06 cd 60-7.5 52.65 ab 49.45 ab 66.09 b 28.32 b 60-15 54.54 a 50.50 a 70.57 a 31.21 a 60-22.5 53.06 ab 47.56 c 62.75 c 25.61 c LSD (p<0.05) 2.45 1.38 2.44 1.58

Values are averages of four replications

191

Plant height

ANALYSIS OF VARIANCE TABLE

K Value

Source Degrees of Freedom

Sum of Squares

Mean Square

F Value

probability

2 N Fert. (A) 2 2278 1139 1633.24 0.00 4 CaC2 (B) 3 68 22.58 32.38 0.00 6 AB 6 13 2.33 3.34 0.01 -7 Error 36 25 0.69 Total 47 2385

Coefficient of Variation 1.00 % Total number of tillers

ANALYSIS OF VARIANCE TABLE

K

Value Source Degrees of

Freedom Sum of Squares

Mean Square

F Value

probability

2 N Fert. (A) 2 834 417 307.95 0.00 4 CaC2 (B) 3 196.5 65.5 48.38 0.00 6 AB 6 52.6 8.8 6.47 0.00 -7 Error 36 48.8 1.35 Total 47 1131.9

Coefficient of Variation 5.68 % Number of fertile tillers

ANALYSIS OF VARIANCE TABLE

K

Value Source Degrees of

Freedom Sum of Squares

Mean Square

F Value

probability

2 N Fert. (A) 2 902.8 451.4 310.7 0.00 4 CaC2 (B) 3 123.7 41.2 28.4 0.00 6 AB 6 43.2 7.2 5.0 0.00 -7 Error 36 52.3 1.4 Total 47 1122.0

Coefficient of Variation 7.46 %

192

Spike length

ANALYSIS OF VARIANCE TABLE

K

Value Source Degrees of

Freedom Sum of Squares

Mean Square

F Value

probability

2 N Fert. (A) 2 22.82 11.41 131.58 0.00 4 CaC2 (B) 3 3.55 1.18 13.67 0.00 6 AB 6 1.14 1.19 2.18 0.07 -7 Error 36 3.12 0.08 Total 47 30.63

Coefficient of Variation 3.06 % Number of spikelets per spike

ANALYSIS OF VARIANCE TABLE

K

Value Source Degrees of

Freedom Sum of Squares

Mean Square

F Value

probability

2 N Fert. (A) 2 235.57 117.78 389.40 0.00 4 CaC2 (B) 3 4.41 1.47 4.86 0.00 6 AB 6 1.77 0.29 0.97 -7 Error 36 10.88 0.30 Total 47 252.64

Coefficient of Variation 3.77 % Number of grains per spike

ANALYSIS OF VARIANCE TABLE

K

Value Source Degrees of

Freedom Sum of Squares

Mean Square

F Value

probability

2 N Fert. (A) 2 305.64 152.82 52.41 0.00 4 CaC2 (B) 3 148.14 49.38 16.93 0.00 6 AB 6 18.47 3.07 1.05 0.41 -7 Error 36 104.96 2.92 Total 47 577.21

Coefficient of Variation 3.43 %

193

1000-grains weight

ANALYSIS OF VARIANCE TABLE

K

Value Source Degrees of

Freedom Sum of Squares

Mean Square

F Value

probability

2 N Fert. (A) 2 326.31 163.15 175.19 0.00 4 CaC2 (B) 3 47.49 15.83 17.00 0.00 6 AB 6 14.02 2.34 2.51 0.03 -7 Error 36 33.52 0.93 Total 47 421.35

Coefficient of Variation 2.08 % Biological yield

ANALYSIS OF VARIANCE TABLE

K

Value Source Degrees of

Freedom Sum of Squares

Mean Square

F Value

probability

2 N Fert. (A) 2 6938.9 349634 1198.8 0.00 4 CaC2 (B) 3 991.9 330.6 114.2 0.00 6 AB 6 349.7 58.3 20.1 0.00 -7 Error 36 104.2 2.9 Total 47 8384.8

Coefficient of Variation 3.43 % Grain yield

ANALYSIS OF VARIANCE TABLE

K

Value Source Degrees of

Freedom Sum of Squares

Mean Square

F Value

probability

2 N Fert. (A) 2 1137.4 568.7 469.4 0.00 4 CaC2 (B) 3 181.5 60.5 49.9 0.00 6 AB 6 64.1 10.7 8.8 0.00 -7 Error 36 43.6 1.2 Total 47 1426.7

Coefficient of Variation 5.09 %

194

% N in straw

ANALYSIS OF VARIANCE TABLE

K Value

Source Degrees of Freedom

Sum of Squares

Mean Square

F Value

probability

2 N Fert. (A) 2 0.32 0.161 1461.5 0.00 4 CaC2 (B) 3 0.008 0.003 23.8 0.00 6 AB 6 0.001 0.0001 0.98 -7 Error 36 0.004 0.0001 Total 47 0.335

Coefficient of Variation 2.19 % % N grain

ANALYSIS OF VARIANCE TABLE

K

Value Source Degrees of

Freedom Sum of Squares

Mean Square

F Value

probability

N Fert. (A) 2 3.11 1.56 6029 0.00 CaC2 (B) 3 0.07 0.02 93.09 0.00 AB 6 0.004 0.001 2.57 0.04 Error 36 0.009 0.0004 Total 47 3.20

Coefficient of Variation 0.83 % Nitrogen uptake by straw

ANALYSIS OF VARIANCE TABLE

K

Value Source Degrees of

Freedom Sum of Squares

Mean Square

F Value

probability

N Fert. (A) 2 0.15 0.077 670.2 0.00 CaC2 (B) 3 0.01 0.004 37.3 0.00 AB 6 0.004 0.001 6.0 0.00 Error 36 0.004 0.0001 Total 47 0.176

Coefficient of Variation 7.62 %

195

Nitrogen uptake by grain

ANALYSIS OF VARIANCE TABLE

K Value

Source Degrees of Freedom

Sum of Squares

Mean Square

F Value

probability

2 N Fert. (A) 2 1.01 0.50 907.77 0.00 4 CaC2 (B) 3 0.10 0.03 63.01 0.00 6 AB 6 0.04 0.01 11.01 0.00 -7 Error 36 0.02 0.001 Total 47 1.17

Coefficient of Variation 5.43 % Agronomic efficiency

ANALYSIS OF VARIANCE TABLE

K Value

Source Degrees of Freedom

Sum of Squares

Mean Square

F Value

probability

1 Replication 3 2.82 0.94 0.14 2 Factor A 7 510.24 72.89 10.47 0.00 -3 Error 21 146.19 6.96 Total 31 659.25

Coefficient of Variation 15.56 % Physiological efficiency

ANALYSIS OF VARIANCE TABLE

K Value

Source Degrees of Freedom

Sum of Squares

Mean Square

F Value

probability

1 Replication 3 3.49 1.17 0.24 2 Factor A 7 101.07 14.44 2.93 0.03 -3 Error 21 103.54 9.93 Total 31 208.11

Coefficient of Variation 6.79 %

196

Apparent nitrogen recovery ANALYSIS OF VARIANCE TABLE

K

Value Source Degrees of

Freedom Sum of Squares

Mean Square

F Value

probability

1 Replication 3 15.36 5.12 0.18 2 Factor A 7 3443.37 491.91 16.99 0.00 -3 Error 21 607.9 28.95 Total 31 4066.62

Coefficient of Variation 10.49 %

197

ANNEXURE VIII

Growth and Yield Response of Wheat to Soil Applied Calcium Carbide

under Field Conditions

Var

iety

Formulation

CaC2 (kg ha-1)

Plant height

Number of tillers

Number of spikes

1000-grains weight

Biological yield

Straw yield

0 92.5 309.7 257.3 46.2 8838.3 4401.7

15 91.2 349.3 281.3 46.3 10780.7 5647.3

30 88.4 387.6 330.7 46.8 11736.7 6086.7

Mat

rix-

I

45 88.07 380.4 319.7 46.2 11410.0 5870.0

0 92.5 310.6 259.0 45.9 8800.0 4376.7

15 91.0 334.9 289.6 46.0 10303.7 5193.7

30 89.7 361.5 305.3 46.5 11572.7 6036.0

Mat

rix-

II

45 87.9 357.5 302.0 46.6 11718.7 6135.3

0 92.5 310.0 258.7 45.5 8773.0 4369.7

15 91.7 340.5 282.7 45.3 10533.3 5383.3

30 90.3 344.5 291.0 46.2 11015.3 5585.3

Inqu

lab-

91

Pain

t coa

ted

CaC

2

45 89.3 353.6 294.0 46.8 11006.0 5496.0

0 92.6 336.6 284.7 47.9 9771.7 5115.0

15 90.0 388.0 321.0 48.8 10836.3 5493.0

30 87.8 420.9 371.0 49.6 12762.7 6749.3

Mat

rix-

I

45 86.2 412.4 359.3 48.8 12279.3 6429.3

0 92.5 338.3 285.3 47.5 9128.3 4548.3

15 91.6 356.6 320.3 47.7 11175.7 5812.3

30 88.4 402.1 339.3 48.4 11937.0 6167.0

Mat

rix-

II

45 87.8 414.8 335.7 48.4 11945.3 6112.0

0 92.6 341.3 285.0 47.7 9335.7 4719.0

15 91.3 371.3 312.3 48.3 10963.0 5589.7

30 89.3 394.4 338.0 48.5 11672.0 5995.3

Bha

khar

-200

2

Pain

t coa

ted

CaC

2

45 89.0 409 342.3 48.7 12515.3 6745.3

198

Var

iet

y

Formulation

CaC2 (kg ha-1)

Grain yield

% N straw

% N grain

N uptake straw

N uptake grain

0 4436.7 0.55 2.10 24.4 93.3

15 5133.3 0.56 2.19 31.8 112.8

30 5650.0 0.58 2.31 35.3 130.5 M

atri

x-I

45 5540.0 0.58 2.39 34.2 132.6

0 4423.3 0.55 2.11 24.1 93.19

15 5110.0 0.55 2.15 28.7 109.7

30 5536.7 0.57 2.29 34.4 127.2

Mat

rix-

II

45 5583.3 0.57 2.35 34.9 131.4

0 4403.3 0.55 2.10 24.0 92.5

15 5150.0 0.55 2.13 29.8 109.7

30 5430.0 0.56 2.26 31.4 122.5

Inqu

lab-

91

Pain

t coa

ted

CaC

2

45 5510.0 0.57 2.31 31.1 127.1

0 4656.7 0.53 2.02 27.3 93.9

15 5343.3 0.54 2.14 29.6 114.2

30 6013.3 0.56 2.22 37.8 133.5

Mat

rix-

I

45 5850.0 0.57 2.29 36.4 133.8

0 4580.0 0.53 2.01 24.1 91.9

15 5363.3 0.54 2.09 31.4 111.9

30 5770.0 0.55 2.20 33.9 126.9

Mat

rix-

II

45 5833.3 0.55 2.27 33.8 132.4

0 4616.7 0.53 2.02 25.0 93.1

15 5373.3 0.53 2.09 29.4 112.7

30 5676.7 0.54 2.19 32.6 124.7

Bha

khar

-200

2

Pain

t coa

ted

CaC

2

45 5770.0 0.55 2.24 37.3 129.2

199

Formulation CaC2 (kg ha-1)

Soil ammonium-N Soil Nitrate-N

0 8.83 36.81

15 21.08 26.33

30 29.22 21.66

Mat

rix-

I

45 34.78 18.33

0 9.53 37.00

15 20.26 29.33

30 25.68 24.66

Mat

rix-

II

45 29.27 21.33

0 10.03 35.66

15 18.54 31.33

30 24.17 26.66

Pain

t coa

ted

CaC

2

45 28.29 23.33

Plant height

NALYSIS OF VARIANCE TABLE

K

Value Source Degrees of

Freedom Sum of Squares

Mean Square

F Value

probability

1 Replication 2 0.735 0.367 0.94 2 Factor A 1 4.743 4.743 12.23 0.006 4 Factor B 2 15.289 7.645 19.72 0.0003 6 AB 2 1.34 0.672 1.73 0.2259 -7 Error 10 3.875 0.388 8 Factor C 3 222.466 74.155 41.43 0.000

10 AC 3 3.003 1.001 0.55 12 BC 6 8.419 1.403 0.78 14 ABC 6 4.142 0.690 0.38 -15 Error 36 64.43 1.790

Total 71 328.446 Coefficient of Variation 1.48 %

200

Number of tillers

NALYSIS OF VARIANCE TABLE

K Value

Source Degrees of Freedom

Sum of Squares

Mean Square

F Value

probability

1 Replication 2 64.76 32.38 5.05 0.03 2 Factor A 1 24798.75 24798.7 3864.76 0.00 4 Factor B 2 3293.78 1646.89 256.65 0.00 6 AB 2 249.18 124.59 19.42 0.00 -7 Error 10 64.16 6.42 8 Factor C 3 47498.53 15832.8 720.33 0.00

10 AC 3 1154.49 384.83 17.51 0.00 12 BC 6 2739.72 456.62 20.77 0.00 14 ABC 6 786.07 131.01 5.96 0.00 -15 Error 36 791.27 21.98

Total 71 81440.74 Coefficient of Variation 1.29 % Number of spikes

NALYSIS OF VARIANCE TABLE

K

Value Source Degrees of

Freedom Sum of Squares

Mean Square

F Value

probability

1 Replication 2 20.36 10.18 0.61 2 Factor A 1 22366.1 22366.1 1350.29 0.00 4 Factor B 2 2938.8 1469.43 88.71 0.00 6 AB 2 153.58 76.79 4.63 0.03 -7 Error 10 165.63 16.56 8 Factor C 3 38121.59 12707.19 546.76 0.00

10 AC 3 596.15 198.72 8.55 0.00 12 BC 6 3387.02 564.51 24.29 0.00 14 ABC 6 228.3 38.05 1.64 0.16 -15 Error 36 836.67 23.24

Total 71 68814.32 Coefficient of Variation 1.57 %

201

1000-grain weight

NALYSIS OF VARIANCE TABLE

K

Value Source Degrees of

Freedom Sum of Squares

Mean Square

F Value

probability

1 Replication 2 1.92 0.96 2.09 0.17 2 Factor A 1 84.87 84.87 184.65 0.00 4 Factor B 2 3.32 1.66 3.62 0.06 6 AB 2 1.63 0.81 1.77 0.21 -7 Error 10 4.59 0.46 8 Factor C 3 9.01 3.004 9.71 0.00

10 AC 3 0.77 0.257 0.83 12 BC 6 2.14 0.357 1.55 0.35 14 ABC 6 1.31 0.217 0.70 -15 Error 36 11.13 0.309

Total 71 120.7 Coefficient of Variation 1.18 % Biological yield

NALYSIS OF VARIANCE TABLE

K

Value Source Degrees of

Freedom Sum of Squares

Mean Square

F Value

probability

1 Replication 2 502137 251068 6.46 0.01 2 Factor A 1 7671444 7671444 197.66 0.00 4 Factor B 2 1340561 670280 17.27 0.00 6 AB 2 392301 196150 5.05 0.03 -7 Error 10 388111 38811 8 Factor C 3 87073078 29024359 791.37 0.00 10 AC 3 402813 134271 3.66 0.02 12 BC 6 1544719 257453 7.01 0.00 14 ABC 6 1951592 325265 8.86 0.00 -15 Error 36 1320332 36675

Total 71 102587093 Coefficient of Variation 1.76 %

202

Straw yield

NALYSIS OF VARIANCE TABLE

K Value

Source Degrees of Freedom

Sum of Squares

Mean Square

F Value

probability

1 Replication 2 493748 246874 7.4 0.01 2 Factor A 1 2993904 2993904 90.0 0.00 4 Factor B 2 735200 367600 11.0 0.00 6 AB 2 337816 168908 5.0 0.03 -7 Error 10 332570 33257 8 Factor C 3 28162134 9387378 261.3 0.00

10 AC 3 310896 103632 2.9 0.04 12 BC 6 753364 125560 3.5 0.00 14 ABC 6 1769545 294924 8.2 0.00 -15 Error 36 1293175 35921

Total 71 37182356 Coefficient of Variation 3.39 % Grain yield

NALYSIS OF VARIANCE TABLE

K

Value Source Degrees of

Freedom Sum of Squares

Mean Square

F Value

probability

1 Replication 2 1602 801 0.36 2 Factor A 1 1080450 1080450 479.5 0.00 4 Factor B 2 91602 45801 20.32 0.00 6 AB 2 9025 4512 2.00 0.18 -7 Error 10 22530 2253 8 Factor C 3 16201250 5400416 5341.0 0.00 10 AC 3 21161 7053 6.97 0.00 12 BC 6 171908 28651 28.33 0.00 14 ABC 6 14530 2421 2.39 0.04 -15 Error 36 36400 1011

Total 71 17650461 Coefficient of Variation 2.60 %

203

% N in straw

NALYSIS OF VARIANCE TABLE

K

Value Source Degrees of

Freedom Sum of Squares

Mean Square

F Value

probability

1 Replication 2 0.001 0.0005 11.73 0.00 2 Factor A 1 0.007 0.007 228.89 0.00 4 Factor B 2 0.002 0.001 29.47 0.00 6 AB 2 0.0001 0.00005 0.43 -7 Error 10 0.0001 0.00001 8 Factor C 3 0.007 0.002 38.63 0.00

10 AC 3 0.0001 0.00003 0.43 12 BC 6 0.0001 0.00001 1.06 0.40 14 ABC 6 0.0001 0.00001 0.34 -15 Error 36 0.002 0.00005

Total 71 0.02 Coefficient of Variation 1.44 % % N in grain

NALYSIS OF VARIANCE TABLE

K

Value Source Degrees of

Freedom Sum of Squares

Mean Square

F Value

probability

1 Replication 2 0.001 0.001 1.75 0.22 2 Factor A 1 0.10 0.107 374.8 0.00 4 Factor B 2 0.02 0.010 34.11 0.00 6 AB 2 0.002 0.001 4.22 0.04 -7 Error 10 0.003 0.00003 8 Factor C 3 0.681 0.227 725.37 0.00

10 AC 3 0.004 0.001 4.50 0.00 12 BC 6 0.009 0.002 4.83 0.00 14 ABC 6 0.001 0.0001 0.46 -15 Error 36 0.011 0.0003

Total 71 0.840 Coefficient of Variation 0.84 %

204

N uptake by straw

NALYSIS OF VARIANCE TABLE

K

Value Source Degrees of

Freedom Sum of Squares

Mean Square

F Value

probability

1 Replication 2 7.28 3.64 3.42 0.07 2 Factor A 1 26.1 26.10 24.51 0.00 4 Factor B 2 51.6 25.79 24.22 0.00 6 AB 2 9.21 4.60 4.32 0.04 -7 Error 10 10.64 1.06 8 Factor C 3 1131.4 377.14 272.06 0.00

10 AC 3 12.75 4.25 3.06 0.04 12 BC 6 27.97 4.66 3.36 0.00 14 ABC 6 61.91 10.31 7.44 0.00 -15 Error 36 49.90 1.38

Total 71 1388.79 Coefficient of Variation 3.80 % N uptake grain

NALYSIS OF VARIANCE TABLE

K

Value Source Degrees of

Freedom Sum of Squares

Mean Square

F Value

probability

1 Replication 2 5.00 2.50 0.94 2 Factor A 1 31.35 31.35 11.86 0.00 4 Factor B 2 207.34 103.67 39.24 0.00 6 AB 2 7.59 3.79 1.44 0.28 -7 Error 10 26.42 2.64 8 Factor C 3 16351.43 5450.47 3907.20 0.00

10 AC 3 12.04 4.02 2.88 0.04 12 BC 6 116.14 19.36 13.87 0.00 14 ABC 6 7.21 1.20 0.86 -15 Error 36 50.22 1.39

Total 71 16814.78 Coefficient of Variation 3.02 %

205

Ammonium-N content

NALYSIS OF VARIANCE TABLE

K Value

Source Degrees of Freedom

Sum of Squares

Mean Square

F Value

probability

1 Replication 2 4.77 2.39 4.77 0.08 2 Factor A 2 62.72 31.36 62.69 0.00 -3 Error 4 2.00 0.50 4 Factor B 3 2334.33 778.11 552.42 0.00 6 AB 6 64.82 10.80 7.67 0.00 -7 Error 18 25.35 1.40 Total 35 3494.02

Coefficient of Variation 5.49 % Nitrate-N content

NALYSIS OF VARIANCE TABLE

K

Value Source Degrees of

Freedom Sum of Squares

Mean Square

F Value

probability

1 Replication 2 3.11 1.55 10.06 0.03 2 Factor A 2 74.52 37.26 240.80 0.00 -3 Error 4 0.62 0.15 4 Factor B 3 1217.13 405.71 239.63 0.00 6 AB 6 42.60 7.10 4.19 0.00 -7 Error 18 30.47 1.69 Total 35 1368.46

Coefficient of Variation 4.70 %