Introduction

Chapter - VI

Nutrient pools and flows

Nutrient cycling patterns have been viewed as critical indicators of ecosystem

stability and productivity in natural ecosystems. Van Breemen (1993, 1995) outlined

feedback processes involving primary producers and decomposers resulting into soil

properties that favour primary productivity in terrestrial ecosystems. Higher or lower

nutrient use efficiency positively feeds back into the nutrient cycle, and helps to

increase or decrease soil fertility. These tendencies are further enhanced by secondary

effects such as higher or lower rates of decomposition of litter and hence nutrient

mineralization. Plants may also influence the external inputs and outputs in the plant­

soil system, by affecting the general hydrology and micro-scale physico-chemical

environment. In agroecosystems, natural feed back mechanisms are radically changed

by the management practices.

Replenishment of nutrients depleted as a result of crop harvests and other

nutrient transformation and movement processes can only ensure long term

sustainability of agriCUltural productivity (Harris, 1998). In the semi-arid tropics,

limited information is available on comparative nutrient budget in different crops and

cropping systems. A higher degree of attention has been paid to nitrogen dynamics as

compared to other elements, more so in experimental plots (prasad and Blaise, 1996;

Sharma et aI., 1996). Impacts of trees in amelioration of soil physico-chemical

properties of saline-alkaline soils in experimental plots has also been studied (Bhojvaid

et aI., 1996; Bhojvaid and Timmer, 1998; Singh et al., 1994; Gupta and Kaur, 1998;

Pathak and Dagar, 1998). Farm-level assessment of nutrient balance is lacking. The

objective of this component of study was (a) to evaluate input-output budget of

nitrogen for important crops and cropping patterns subjected to varied irrigation regime

observed in the study village (b) to estimate the impact of different crops on extractable

cations including potassium, sodium, magnesium and calcium.

71

Methods

Three farm fields subjected to each of six dominant rotations wheat-paddy,

wheat-pigeon pea, fallow-sorghum, fallow-pearl millet, fallow-berseem and mustard­

paddy and subjected to different irrigation practices (unirrigated, canal irrigated and

tubewell irrigated areas) were selected in the year 1996. Soil samples were collected

before ploughing in the month of April from all fields for estimating texture, bulk

density, water holding capacity and pH.

Soil texture analysis

For soil texture analysis, the following steps were taken as is given by Okalebo

et al. (1993) is given by Okalebo et al. (1993):

a) 50 gm of air-dry soil (2 mm soils) was saturated with distilled water and then 10

ml of 10% calgon (Sodium hexametaphosphate) solution was added to it. It was

allowed to stand for 10 minutes

b) The suspension was mixed for 2 minutes with an electric high speed stirrer.

c) The suspension was transferred into a graduated cylinder, the remaining soil was

rinsed into the cylinder with distilled water. The hydrometer was inserted into the

suspension and water was added, then hydrometer was removed.

d) The cylinder was covered with a tight-fitting rubber bung and cylinder carefully ten

times and time was noted. Quickly 2-3 drops of amyl alcohol was added to the soil

suspension in order to remove froth and after 20 seconds the hydrometer was

gently placed into the column.

e) At 40 second hydrometer reading was taken and the temperature of the suspension

was measured.

t) Step d (mixing the soil suspension 10 times)was repeated and the cylinder was

allowed to stand undisturbed for 2 hours.

g) After two hours, the hydrometer and temperature readings were taken.

h) The necessary temperature correction was done.

For calculation, it was assumed that after 40 seconds, the sand was settled, and the

72

hydrometer reading reflects the grams of soil and clay in the suspension. After 2

hours, the silt settled, the hydrometer reading reflected the clay content of original

suspension and the silt content was calculated by subtracting the sum of the clay

and sand contents from 100%.

Soil Bulk density estimation methods

The following steps were taken to measure bulk density-firstly 2 cm of surface

soil were removed then a thin-sheet metal tube of 5 cm diameter of known weight (w)

and volume (v) 5 cm3 was inserted into-the soil surface. Then the soil were cut beneath

the tube bottom after excavating the soil from around the tube and simultaneously the

excess soil from the tube ends were removed by using knife. This was dried at 105° C

for two days and weighed (W2). The soil bulk density was calculated by using the

following formula i.e. W2-Wl g/cm3N.

Nutrient analysis methods

Soil pools of exchangeable cations and total nitrogen in 0-15 cm and 15-30 cm

soil horizons were estimated at two points of time: just before sowing the crop and just

after harvesting of each crop. For estimation of soil nutrient pools, 15 samples from

each field were mixed thoroughly to give a composite sample for a given depth and a

given field. Samples were air dried and passed through a 210 J.lll1 sieve. Cations were

extracted in 1M ammonium acetate solution (5 g air dried sieved soil in 100 ml of 1M

ammonium acetate solution at pH 7) and their concentrations were determined by

atomic absorption spectrophotometer (PU9200X Philips, England). Soil nitrogen was

estimated by the Kjeldahl method. Nutrient pools on area basis (kg/ha) were computed

using bulk density and concentration values. The quality and quantity of fertilizer

applied to different crops were monitored. Amount of nutrient added through fertilizer

were calculated based on the quantity and chemical composition of the fertilizer.

73

Crop and weed biomass were estimated as already described in Chapter 4.

Biomass of each crop was separated into roots, shoot (stems+leaves), grains and husk.

Weed biomass (all weed species were pooled) was separated into aboveground and

belowground organs. Oven dried (oven drying at 80+50C for 48 hours) material was

ground in a mill and the material was passed through Imm sieve. Kjeldahl method was

used for estimating nitrogen concentration in plant tissue (Allen, 1989). Nitrogen

accumulations in different parts of crop/weed were calculated based on nitrogen

concentration and biomass of respective part.

Crop and weed biomass were also separated into four flow components:

biomass used as human food, biomass used as fodder, biomass subjected to fire and

biomass incorporated as residue within the field. Nitrogen flows through these four

components were quantified by multiplying the concentration and quantity of each flow

component.

Soil pH measurement

Soil pH was measured in 1 :2.5 soil : water suspension. Soil (20 g) with

deionized water (50 ml) was stirred for 10 minutes, allowed to stand for 30 minutes,

again stirred for 2 minutes, and then the pH of the soil suspension was measured by a

digital pH meter (model LI-127 Elico).

Results Basic soil properties

Soil texture, bulk density, water holding capacity and pH did not differ

significantly (P>0.05) between 0-15 cm and 0-30 cm soil horizons in a given land use

type. Mean values for these parameters for 0-30 cm soil column are given in Table 6.1.

Sand was the most dominant component of soil particles in all the three land use types

accounting for about 50% of soil in tubewell irrigated area compared to 57.6% in

unirrigated area and 58.7% in canal irrigated area. Though significant differences were

observed in clay and silt proportions between three land use types, bulk density and

74

water holding capacity did not differ significantly. Canal irrigated area showed the

highest pH (9.00) followed by tubewell irrigated area (8.21) and unirrigated area (7.26).

Nitrogen accumulation in plant biomass

Winter crops

Nitrogen accumulation in plant biomass (crop+weed component) varied from

about 75 kg/ha in unirrigated wheat crop to about 125 kglha in tubewell irrigated

berseem crop. Irrigation had a significant effect on nitrogen uptake. Nitrogen

accumulation by unirrigated wheat crop was substantially lower than that by irrigated

crops. Comparison of wheat crop raised in three land use types, showed significantly

larger quantity of nitrogen in weed component in canal irrigated area (9. 74 kg/ha) as

compared to the tubewell irrigated (7.5 kglha) and unirrigated systems (4.94 kg/ha). In

. berseem grown only in two types of land use systems, nitrogen accumulation in

irrigated crop (124.68 kg/ha) was higher than that in unirrigated crop (103.l4 kg/ha).

Nitrogen in belowground weed biomass was negligible. Among the crops, nitrogen in

belowground component of berseem was over two times of that in case of wheat and

mustard (Fig. 6.a).

Rainy season crops

Nitrogen accumulation in four rainy season crops in different land use systems

IS shown in Fig. 6.b. Except for canal irrigated Sorghum, nitrogen pool in plant

biomass was higher in irrigated areas as compared to the unirrigated area for a given

crop. Nitrogen accumulation by pigeon pea, a crop grown only in unirrigated land use,

was the highest among all crops. About 45% of nitrogen uptake was accounted by grain

component in non-nitrogen fixing cereal crop paddy compared to about 35% in

nitrogen fixing pigeon pea. Nitrogen in weed component of irrigated paddy crops was

over two times of that observed in other crops. Nitrogen accumulated in be1owground

organs was highest in pigeon pea followed by sorghum, pearl millet and paddy in

comparable land uses.

Nitrogen input pools

Winter crops

75

Nitrogen available for crop growth in the system is presented in Fig. 6.c. Inputs

available through irrigation water or rainfall were not measured, a limitation of this

study. Except for unirrigated berseem and wheat crops, nitrogen content was higher in

the upper horizon (0-15 cm) as compared to the lower horizon (15-30 cm). Soil -

nitrogen was higher in unirrigated system as compared to that in irrigated system in

both wheat and berseem crops. Soil nitrogen available in the field in the fonn of crop

residues of the previous crop varied between 1.88 kg/Ita to 3.34 kglha across crops and

land use types and was negligible when compared with soil bound organic and

inorganic nitrogen. Nitrogen input through fertilizers applied in the fonn of DAP and

urea in wheat mustard was less than 5% of soil nitrogen in all the cases. This input was

higher in irrigated system as compared to that in the unirrigated system.

Rainy season crops

In all crops, soil nitrogen content in 0-15 cm horizon was nearly equal to that in

15-30 cm horizon as shown in fig. 6.d. Soil nitrogen content was similar for different

crops in a given land use type, except for pigeon pea. Soil under pigeon pea under

unirrigated condition had significantly larger quantity of nitrogen (2953 kglha in 0-30

cm horizon) as compared to an average of2458.10 kglha in other unirrigated croplands.

Nitrogen flows

Winter season crops

Quantities of nitrogen flows through four major path ways [(1) nitrogen

incorporated in human food component that is partly consumed within the village and

partly exported (2) nitrogen incorporated in plant biomass (crop as well as weed

component) fed to the livestock (3) nitrogen loss due to burning of crop residues (partly

as surface fire after harvesting in the field and partly as a result of burning for cooking)

76

and (4) nitrogen present in plant residues incorporated in situ] are depicted in Fig. 6.c.

Loss of nitrogen as a result of burning was higher from irrigated as compared to

unirrigated crops of wheat and berseem. The highest level of this loss was observed in

mustard followed by wheat and berseem. Except for application in seedling raising of

paddy, organic manuring is not at all practiced in the study area. Dung from cattle is

used to prepare dung cakes which constitute the major energy source. Thus, nitrogen

movement through fodder component also could be viewed as loss due to burning. The -

amount of nitrogen recycled back to the site in the form of crop and weed residues was

highest in berseem followed by mustard and wheat. In case of wheat, nitrogen

incorporated through residues was higher in unirrigated crop as compared to the

irrigated crop while the reverse was observed for berseem crop.

Rainy season crops

Among the rainy season crops, the highest levels of nitrogen recycled through

residues and that lost through burning were observed in pigeon pea. In general, losses

through burning were higher in irrigated systems as compared to the unirrigated ones

(Fig.6.t).

Impact of cropping on exchangeable cations, total nitrogen and organic carbon

Soils across crops, sowing and harvesting time samplings and land use systems

showed the highest quantities of calcium followed by sodium, magnesium and

potassium. Potassium content varied from 190 to 312 kg/ha (Table 6.2), magnesium

from 524 to 883 kg/ha (Table 6.3), calcium from 1497 to 7763 kg/ha (Table 6.4) and

sodium from 445 to 2145 kg/ha (Table 6.5). Exchangeable sodium content increased

due to cropping in all winter season crops except for tubewell irrigated berseem crop

and this increase was most pronounced in wheat crop. In the rainy season crops, an

increase was observed in tubewell irrigated paddy, unirrigated and tubewell irrigated

sorghum, and unirrigated pearl millet. Except for unirrigated paddy and pigeon pea,

exchangeable potassium declined after harvesting among rainy season crops and

77

increased in winter season crops except for tubewell irrigated wheat and unirrigated

berseem where a decline was observed. Exchangeable calcium increased due to

cultivation of all winter season crops and declined due to cultivation of all rainy season

crops excluding tubewell irrigated sorghum and unirrigated pigeon pea.

Soil nitrogen quantities declined due to cropping and harvesting in all winter

crops. In the rainy season crops, there was an increase in soil nitrogen status in all

unirrigated systems·but a depletion in all irrigated systems except for tubewell irrigated

paddy crop. Increase in soil nitrogen status due to cropping was highest in pigeon pea

(an increase of 4962 kg/ha of soil kjeldahl nitrogen) followed by unirrigated paddy crop

(2184 kg/ha) (Table 6.6). Soil organic carbon level increased in winter crops and

decreased in all rainy season crops (Table 6.7).

Nitrogen use efficiency

The scope of nitrogen use efficiency here is limited to (a) to what extent

fertilizer N input met the uptake in the system (b) the agronomic efficiency of fertilizer

use in tenns of kg grain or fodder produced per kg of fertilizer applied. Except for

pigeon pea where diammonium phosphate was applied, urea was applied in single doze

in all rainy season crops. In winter season crops, urea was applied in berseem crop and

urea plus diammonium phosphate in wheat and mustard. Higher quantities of inputs

were applied in irrigated crops as compared to the unirrigated ones except for paddy

and pearl millet where similar quantities of fertilizer were applied in both irrigated and

unirrigated systems. Irrigated wheat crop received the highest level of nitrogen fertilizer

input (196.37 kg-N/ha) and unirrigated sorghum crop the lowest (9.2 kg-N/ha). In

wheat, nitrogen accumulated in crop and weed, biomass accounted for 87% of input

through fertilizer in unirrigated system and about 50% in the irrigated system. In

mustard and berseem, nitrogen in plant biomass exceeded the quantities applied

through fertilizer. In the rainy season crops, in paddy nitrogen accumulated in plant

biomass was nearly equal to that applied through fertilizer while in all other crops it

78

was much more than the fertilizer input. Except for paddy, grain or fodder yield per

unit of fertilizer N input was higher in unirrigated conditions as compared to the

irrigated conditions (Table 6.8).

Discussion

Semiarid tropical soils generally contain less than 1 % organic carbon and less

than 0.1 % total nitrogen content ((Virmani et aI., 1982; Tandon and Kanwar, 1984).

However, departures from these broad generalizations may occur in intensively

managed agroecosystems faced to different levels of salinity-alkalinity, small scale

variation in texture and management regime (Brar and Singh, 1984; Bhojvaid and

Timmer, 1998). In the present study organic carbon percentage varied from 0.15% to

0.80% and organic nitrogen from 0.06% to 0.29% across crops, sampling times and

irrigation practices. The trend in exchangeable cations Ca> Mg > K reported here is

observed by others in comparable ecological conditions (Bhojvaid and Timmer, 1998).

Nutrient accumulation in crops depends upon the eco-physiological attributes

of the crop/cultivar, availability of nutrients and synchrony between supply of available

forms of nutrients from the soil with the demands by crop (Woomer and Swift, 1994).

Nitrogen accumulation under a range of fertilizer and crop residue inputs and subjected

to the recommended agronomic practices under experimental conditions is reported in

the range from 101 to 148 kg/ha in wheat crop and in sorghum about 201 kg/ha

(Sharma et aI., 1996) compared to 76.28-100.16 kg/ha in wheat and 53-87.58 kg/ha in

sorghum in the present case. This difference between vigour of growth between

experimental plots and farmer's plots shows that farmers are unable to realize the

maximum possible yields and recycle nitrogen partly because of inherent ecological

constraints and partly because of inappropriate management practices. A comparison of

fertilizer inputs in the study area with that in other comparable agroecological zones

(Sharma et al., 1996; Sarkar, 1997; Raghav and Pal, 1994; Bhu Dayal et al., 1995)

shows that inputs in the present case are much higher than the recommended dozes.

79

Availability of fertilizers at highly subsidized price and conception among farmers,

higher the fertilizer input, higher the yield, could be the reasons behind uses exceeding

the recommended dozes.

Urea is the most common fertilizer input as also applicable on a regional or

national scale. A precise evaluation of fertilizer use or recovery efficiency requires

more sophisticated techniques such as use of radio active tracers ((Katyal, 1993).

However, a net input and output budget as attempted in this study does indicate the

efficiency of nutrient use in the system. The addition of fertilizer is subject to diverse

processes - uptake by crop and weeds, immobilization by microbes or losses through

run-off, leaching and denitirification. The rate of these processes are affected by soil

physico-chemical properties as influenced by the management practices and crop

growth. Situations, such as paddy and wheat cropping where nitrogen input through

fertilizers is equal to or more than that incorporated in plant biomass indicate lesser

dependence on nutrients released through decomposition and mineralization of soil

organic matter and crop residues. A negative balance of soil nitrogen level despite of a

high level of fertilizer input and low level of accumulation in biomass in wheat crop

suggests inefficient utilization of this critical nutrient as compared to berseem receiving

lower input but accumulating larger quantities within biomass. This is also true when

paddy is compared with other rainy season crops. Losses through run-off, leaching and

denitrification are likely to be higher in these crops as compared to others. On the other

hand, fodder crops and leguminous pigeon pea seem to satisfy their needs partly

through fertilizer input and partly through release from mineralization and thus

conserve nitrogen more effectively within the system. These crops also produce higher

quantity of nutrient in the belowground plant residues which escape the damaging

effects of fire and thus recycled back to the system. Thus continued imposition of

wheat-paddy rotation is likely to accompany less efficient cycling of nitrogen.

80

The trends. in changes in exchangeable cations and total nitrogen were not

correlated with soil organic matter content indicating diverse patterns of uptake and

release of different organic/inorganic constituents by different species. The changes in

soil nutrient pools have been reported to be more strongly correlated with active pools

of soil organic carbon than the total organic carbon content (Patron et al., 1987; Wood

et af., 1990).

Agricultural land use intensification may lead to higher. levels of soil

productivity provided practices promoting recycling and conservation of nutrients are

practiced. Readily available nutrients in the form of fertilizers stimulate plant growth in

the absence of water stress and higher rates of crop growth rates may result in increase

in quantities of organic matter added to the soil through rhizodeposition (Singh et al.,

1983; Tisdale and Nelson, 1970). However, practices like application of larger

quantities of nutrients in unirrigated conditions and irrigation with saline water

particularly in tubewell irrigated areas could synchronize release of nutrients and

uptake by crops, leading to tremendous losses through leaching and run-off. Existence

of a network of traditional ponds seemed to provide an advantage for retention of run­

off losses and their recycling through pond based irrigation. Filling in of these ponds

and cultivation over these areas seem to have blocked an important· process of

conservation on a landscape scale. Similarly, earlier a substantial portion of nutrient

removed through fodder component used to be recycled in the form of organic manure,

a practice which is virtually non-existent now. Losses of nitrogen a key element

limiting biological productivity in arid and semiarid warm areas (Katyal, 1993), are

indeed much lower than those noted for traditional shifting agriculture (Ramakrishnan,

1992) but would be substantial over long periods of time. Further, nitrogen

mineralization process may be stimulated by fire (Saxena and Ramakrishnan, 1993)

practiced at a time when crop growth has not initiated.

81

The amount of nitrogen added in the form of fertilizer is substantially lower

than the quantities present as kjeldahl digestible nitrogen in oil in all crops and land use

systems. Thus, nutrient recycling processes could sustain crop productivity provided

synchrony is established between nutrient release and uptake process. Establishment of

synchrony could be achieved by manipulating the organization of the agroecosystem

together with manipulation of residue quality and placement. Further, alluvial soils in

Puunjab Haryana region are quite deep and moderately sandy in many areas as in the

present case. Substantial quantities of nutrients are transported down, particularly the

more labile nutrients like nitrate and potassium. These nutrients reaching beyond the

rooting zone of annual agricultural crops could be pumped up through agroforestry

trees and recycled back to the surface soil through nutrient cycling (Fisher, 1990).

Some agroforestry trees in the region have been found to be quite effective in

alleviation of sodium toxicity (Bhojvaid and Tirnmer, 1998). However, the density of

agroforestry trees seem to have declined in the recent years and this could be another

threat to depletion of soil fertility in the long run (plate no. 3 & 4).

Table 6.1 : Soil (0-30 cm) physico-chemical properties (mean ± standard deviation, n = 8) of unirrigated, canal irrigated and tubewell irrigated land uses.

Landuse

Soil property Unirrigated Canal irrigated Tubewell irrigated Least significant difference (P=O.05)

Texture Clay 21.5±.07 12.0±0.5 13.5±0.7 0.26 Silt 57.6±1.2 58.7±l.I 49.6±.9 0.40 Sand 20.9±.9 29.3±0.8 36.9±0.7 0.35

Bulk density 1.26±0.03 1.25±0.03 1.26±0.04 0.072 Water holding 41.20±0.85 38.7l±1.20 40.47±1.05 0.40 capacity -PH 7.26±0.38 9.00±0.30 8.21±0.14 0.205

Table 6.2 : Soil exchangeable potassium (kg/ha) in 0-15 em, 15-30 em and total quantity in 0-30 em horizon in different crops and land uses

Crop and land use type Before Sowing After Sowing

0-15 em 15-30 em Total 0-15 em 15-30 em Total Net Balance

Wheat Unirrigated 116.55±1.09 115.29±3.78 231.84 124.75±1.89 122.85±5.67 247.6 +15.76 Canal irrigated 103.37±4.97 87.07±2.17 190.44 118.61±1.57 116.61±6.62 235.22 +44.78 Tubewell irrigated 116.10±1.09 101.58±2.89 217.68 109.16±1.09 103.48±1.09 212.64 -5.04

Berseem Unirrigated 137.05±5.84 138.33±4.81 275.38 147.26± 1.91 100.08±2.21 247.34 -28.04 Tubewell irrigated 128.20±3.66 89.06±2.11 217.26 130.54±2.79 96.99±1.83 227.53 +10.27

Mustard Unirrigated 139.61±2.13 134.65±1.87 274.26 145.00±3.14 141.36±2.95 286.36 +12.1

Paddy . Un irrigated 109.62±5.67 111.51±3.98 221.13 116.55±1.09 115.29±3.78 231.84 +10.54 Canal irrigated 95.22±6.04 104.62±6.60 199.84 103.37±4.97 87.07±2.17 190.44 -9.40 Tubewell irrigated 133.13±6.08 129.35±6.08 262.48 116.1±1.09 101.58±2.89 217.68 -44.80

Sorghum Un irrigated 169.57±5.84 139.60±6.62 309.17 137.05±5.84 138.33±4.81 275.38 -33.79 Canal irrigated 162.68±5.06 149.29±3.83 311.97 90.59±1.10 93. 14±3.98 183.73 -128.24 Tubewell irrigated 138.10±11.13 95.77±2.11 233.87 128.1O±3.66 89.06±2.l1 217.16 -16.71

Pearl millet Unirrgated 169.57±5.84 139.60±6.62 309.17 137.05±5.84 . 138.33±4.81 275.38 -33.79

Canal irrigated 162.68±5.06 149.29±3.83 304.97 90.59±1.10 93.14±3.98 183.73 -21.24

Pigeon Pea Un irrigated 113.4±3.11 84.11±4.65 197.51 110.65±2.39 93.73±3.77 204.38 +6.87

Table 6.3 : Soil exchangeable magnesium (kglha) in 0-15 em, 15-30 em and total quantity in 0-30 em horizon in different crops and land uses

Crop and land use type Before Sowing After Sowing

0-15 em 15-30 em Total 0-15 em 15-30 em Total Net Balance

Wheat Un irrigated 269.88±11.13 294.58±11.17 564.46 344.86±11.28 360.99±18.82 705.85 +141.39 Canal irrigated 296.08±9.76 293.94±8.19 590.02 414.30±9.76 418.55±3.19 832.85 +242.83 Tubewell irrigated 400.11±9.82 369.00±26.79 769.11 691.24±16.85 355.06±13.00 1046.3 +277.19

Berseem Un irrigated 441.08±6.77 313.19±19.04 754.27 395.56±6.76 348.96±11.41 744.52 -9.75 Tubewell irrigated 422.05±12.56 352.57±10.92 774.62 383.68±9.99 331.83±10.92 715.51 -59.11

Mustard Un irrigated 251.8+16.80 273.11 +9.60 524.91 296.33+9.11 342.86+ 12.81 639.19 + 114.28

Paddy Un irrigated 367.24±1.95 314.87±3.21 682.11 269.88±11.13 294.58±11.17 564.46 -117.65 Canal irrigated 355. 19±6.04 359.98±6.65 715.17 269.08±9.76 293.94±8.19 563.02 -152.15 Tubewell irrigated 372.22+3.71 314.29±4.91 686.51 400.11 +9.82 363 .00±26. 79 769.11 +82.60

Sorghum Unirrgated 381.47±4.96 352.21±8.17 733.68 441.08±6.77 313.19±19.00 754.27 20.59 Canal irrigated 368.76±3.75 309.10±3.25 677.86 323.20±29.52 313.44±7.5 636.64 -41.22 Tubewell irrigated 401.33+3.11 310.05+9.50 711.38 422.05±12.56 352.57±10.92 774.62 +63.24

Pearl millet Unirrgated 381.47±4.96 352.21±8.17 733.68 441.08±6.77 313.19±19.04 , 754.27 +20.59

Canal irrigated 368.76±3.75 309.10±3.25 677.86 323.20±29.52 313.44+7.51 636.64 -41.22

Pigeon Pea Un irrigated 434.82+4.90 447.21+4.18 882.03 376. 15±9.62 373.09±4.92 749.24 -132.79

Table 6.4 : Soil exchangeable calcium (kg/ha) in 0-15 cm, 15-30 cm and total quantity in 0-30 cm horizon in different crops and land uses

Crop and land use type Before Sowing After Sowing

0-15 em 15-30 em Total 0-15 em 15-30 em Total Net Balance

Wheat Unirrigated 1241.56±4.06 1126.09±8.44 2367.65 1539.53±6.87 1418.06±6.05 2957.59 +589.94 Canal irrigated 2625.79±13.77 3245.74±6.39 5871.53 3632.54±14.44 4130.69±6.37 7763.23 +1891.7 Tubewell irrigated 893.80±10.45 860.33± 10.13 1754.13 1442.29+9.31 1074.08+6.96 2516.37 +762.24

Berseem Unirrigated 979.85±17.93 1163.81±25.49 2143.66 1385.01±9.54 1144.52±6.26 2529.53 +385.87 Tubewell irrigated 1051.37+17.91 930.12± 12.65 1981.49 1225.78+8.36 1055.72+11.03 2281.5 +300.01

Mustard Unirrigated 1334.00±4.59 1031.00±3.12 2365 1630.00±4.43 1214.16±3.5 2844 +479

Paddy Unirrigated ' 1559.13±2.81 1426.14±13.46 2985.27 1241.56±4.06 1126.09±8.44 2367.65 -617.62 Canal irrigated 3753.11±9.66 3536.49±22.24 7289.6 2625.79±13.77 3245.74±6.39 5871.53 -1418.07 Tubewell irrigated 1055.51±6.82 884.16± 10.42 1939.67 893.8±10.45 860.33±1O.13 1754.13 -185.54

Sorghum Unirrigated 1883.15±11.61 1855.12±1O.74 3738.27 979.85±17.93 1163.81±25.49 2143.66 -1594.61 Canal irrigated 3445.13±13.12 3031.06± 16.88 6476.19 2027.1O±11.16 2446.84±6.04 4473.94 -2002.25 Tubewell irrigated 992.54±5.45 862.56±8.40 1854.10 1051.37±17.19 930.12± 12.56 1981.49 +126.39

Pearl millet Unirrgated 1883.15±11.61 1855.12±1O.74 3688.27 979.85±17.93 1163.81±25.49 2143.66 -1544.61

Canal irrigated 3445.13±13.12 303.l.06±16.88 6476.19 2027.10±11.16 2446.84+6.04 4473.94 -2002.25

Pigeon Pea Unirrigated 820.65+7.98 677.27+8.70 1497.92 1833.05+12.17 2127.25+8.60 3961 +2463.08

Table 6.5 : Soil exchangeable sodium (kg/ha) in 0-15 em, 15-30 em and total quantity in 0-30 em horizon in different crops and land uses

Crop and land use type Before Sowing After Sowing

0-15 em 15-30 em Total 0-15 em 15-30 em Total Net Balance

Wheat Un irrigated 306.18±8.23 326.97±6.54 633.15 1015.56±2.88 1038.24±17.l4 2053.8 +1420.65 Canal irrigated 326.40±5.74 347.7±6.77 674.1 369.00±7.11 716.71±2.86 1085.71 +411.61 Tubewell irrigated 502.27±8.53 533.82±13.25 1036.09 1117.49±9.71 1027.89±1O.01 2145.38 +1109.29

Berseem Un irrigated 342.33±15.l8 341.69±2.92 684.02 203.99±2.92 707.62±11.94 911.61 +227.59 Tubewell irrigated 665.51±9.21 697.84±9.02 1363.35 924.95±9.68 389.79v9.68 1314.74 -48.61

Mustard I

Un irrigated 386.43±2.56 416.40±3.18 802.83 647.00±12.60 717.43±19.30 1364.43 +561.6 Paddy

Un irrigated 558.18±2.88 294.84±8.66 853.02 306.18±8.23 326.97±6.54 633.15 -219.87 Canal irrigated 645.9l±9.26 486.15±21.37 1132.06 326.40±5.74 347.7±6.77 674.1 -457.96 Tubewell irrigated 436.01±11.09 209.48±6.80 645.49 502.27±8.53 533.82±13.25 1036.09 +390.6

Sorghum Unirrigated 252.45±5.06 193.16±18.44 445.61 342.33±15.18 341.69±2.92 684.02 238.41 Canal irrigated 914.25±10.54 713.27±26.81 1627.52 332.39±5.84 300.49±1.91 632.88 -994.64 Tubewell irrigated 507.52±8.25 269.62±7.39 777.14 665.5l±9.21 697.84±9.02 1363.65 +586.51

Pearl millet Unirrgated 252.45±5.06 193.16±18.44 445.61 342.33±15.18 341.69±2.92 684.02 +238.41

Canal irrigated 914.25±10.54 713.27±26.81 1627.52 332.39±5.84 300.49±1.91 632.88 -994.64

Pigeon Pea Unirrigated 916.65±7.56 611.73±2.88 1528.38 750.92± 12. 74 502. 73±7. 73 1253.65 -274.73

Table 6.6: Soil total nitrogen (kg/ha) in 0-15 em, 15-30 em and total quantity in 0-30 em horizon in different crops and land uses

Crop and land use type Soil depth Soil depth

0-15 em 15-30 em Total 0-15 em 15-30 em Total Change (Total after harvesting- Total at the time of sowing

Wheat Un irrigated 2557.47±152.71 3539.97±43.64 6097.14 2778. ±128.6 1758±86.86 4536 -156l.l4 Canal irrigated 2680.1 6± 1 08.44 2881.27±108.44 5561.43 1259 ±26.58 1504±53.11 2763 -2798.43 Tubewell irrigated 2850.85±152.95 2498.76±65.49 5349.61 1382 ±29.1l 1193±39.5 2575 -2774.61

Berseem Un irrigated 2880.22± 176.65 3511.35±61.46 6391.57 2429 ±73.41 1721±49.87 4150 -2241.57 Tubewell irrigated 3067 .08±27 .94 2238.9±38.6 5305.17 2196 ±49.5 1647±78.53 3843 -1462.17

Mustard Unirrigated 4728.00±57.29 3923.00±34.57 8651.00 2667 ±109.4 2477±71.06 5144 -3507.00

Paddy Unirrigated 1965.6±12296 1946.7±65.39 3912.3 2557.17±152.71 3539.97±43.64 6097.14 +2184.84 Canal irrigated 3195.2±325.15 3732.68±15 1.86 6927.88 2680.16±108.44 2881.27± 108.44 5561.43 -1366.45 Tubewell irrigated 3129.13±424.03 2788.38±43.70 5917.51 2850.85± 152.95 2498.76±65.90 5349.61 +567.90

Sorghum Un irrigated 2229.97±11O.35 2180.25±44.16 4410.22 2880.22± 176.65 3511.35±61.47 6391.37 + 1981.35 Canal irrigated 3188.72±44.02 357l.52± 1 10.43 6760.24 1982.90±61.51 2000. 13±44.19 3983.03 -2777.21 Tubewell irrigated 4512.78±105.59 3696.6± 192. 1 5 8209.38 3067.08±27.94 2238.09±38.6 5305.17 -2904.21

Pearl millet Unirrgated 2229.97±110.35 2180.25±44.l6 4410.22 2880.22± 176.65 3511.35±61.47 6391.57 +1981.35

Canal irrigated 3188.72±44.02 357l.52±110.43 6760.24 1982.90±61.51 2000.13±44.19 3983.03 -2777.21 Pigeon Pea ,

Unirrigated 2858. ±128.41 3048±139.04 5706 5143.5±25.14 5424.5+61.22 10668 +4962

Table 6.7 : Soil total organic carbon (kg/ha) in 0-15 em, 15-30 em and total quantity in 0-30 em horizon in different crops and land uses

Crop and land use type Before Sowing After Sowing

0-15 em 15-30 em Total 0-15 cm 15-30 em Total Net Balance

Wheat Unirrigated 6237±126.63 5481±109.05 11718 737l±189.0 7938±226.9 15309 +3591 Canal irrigated 6954.15±206. 74 5638.5±488.67 12592.65 8081.85±451.08 7330.05±488.67 15411.9 +2819.25 Tubewell irrigated 7572.265.02 4732.5±208.23 12304.5 10032.9±115.47 5489.7±15 1.44 15522.6 +3218.1

Berseem Unirrigated 10718.4±382.8 4593 .6±229 .68 15312 12823.8±191.4 5550.6±153.12 18374.4 +3062.4 Tubewell irrigated 8418±115.29 4575±96.99 12993 8967±237.9 3660±256.2 12627 +366

Mustard U nirrigated 5943±179 4436.73±188 10379.73 6844±136.6 5811.42±219.4 12655.42 +2275.69

Paddy Unirrigated 9261±154.98 7938±141.75 17199 6237±126.63 548l±109.05 11718 -5481 Canal irrigated 8645.7±120.28 7142.1±187.95 15787.8 6954.15±206.74 5638.5±488.05 12592.65 -3195.15 Tubewell irrigated 10790.1±208.23 5679±189.3 16469.1 7572±265.02 4732.5±208.23 12304.5 -4164.6

Sorghum Un irrigated 1 0327.5±21 0.37 9753.75±229.5 20081.25 7076.25±229.5 6693.75±248.62 13770 -6311.25 Canal irrigated 13589.4±344.52 4785±210.54 18374.4 10718.4±382.8 4593.6±229.68 15312 -3062.4 Tubewell irrigated 9516±439.2 5307±96.99 14823 8418±115.29 4575±96.99 12993 -1830

Pearl millet Unirrgated 10327.5±210.37 9753.75±229.5 20081.25 7076.25±229.5 6693.75±248.62 13770 -6311

Canal irrigated 13589.4±344.52 4785±21O.54 18374.4 10718.4±382.8 4593 .6±229 .68 15312 -3062.4

Pigeon Pea Unirrigated 7239±133.35 5334±190.5 12.573 5715±266.7 4191±323.85 9906 -2667

.. Roots (C)

IaI Husk (C)

~ Shoot (C) [==:J Grain (C)

P1HHliil Roots+rhizomes (W) [==:J Shoot (W)

Nitrogen (kg Iha) 140~----------------------~----------------------------------

120

100

80

60

40

20

o . Uni Cai

Wheat Tui Uni Tui

Berseem Uni

Mustard

Fig. 6a. Nitrogen accumulation in different parts of the winter season crop and weed.

Nitrogen (kg/ha) 160~----------------------------------------------------~

140

120

100

80

.. Roots (C)

~ Husk (C)

60L ............................ ~~

40

20

o Uni Cai Tui

Paddy

~ Shoot (C) 1>1 Grain (C) ......................................

!iHHiHWI Roots+rhizome (Wc=J Shoot (W)

Uni Cai Tui Sorghum

Uni Cai P. millet

Fig. 6b. Nitrogen accumulation in different parts of the ra' my season crops and weed.

Uni P. pea

NN~it~r~O~g~e~n~(~k~g~/~h~a~)~(T~h~o~u~s~a~n~d~S~) __ ~ ______ ------------------l 10,-

.. Soil (15-30) ~ Soil (0-15)

8 ~ ..................... .

6

4

2

o Uni Cai

Wheat Tui

[>1 Fertilizer ~ Residue

Uni Tui Berseem

Uni Mustard

Fig. 6c. Soil nitrogen (in 0-15 cm and I5~30 cm horizons) and inputs through fertilizers and residues in different winter season crops ..

Nitrogen (kg Iha) (Thousands) 8~~~~~~~------~---------------------------

7

6

5

4

3

2

1

a

.. Soil (15-30) ~ Soil (0-15) LA Fertilizer ~ Residue

Uni Cai Tui Paddy

Uni Cai Tui

Sorghum Uni Cai

P. millet

Uni Po pea

Fig. 6d. Soil nitrogen (in 0-15 em and 15-30 em horizons) and inputs through fertilizers and residues in different rainy season crops.

140

120

100

80

60

40

20

o

Nitrogen (kg/ha)

.. Human food ~ Fodder

Uni Cai Tui

Wheat Uni Tui

Berseem Uni

Mustard

Fig. 6e. Nitrogen flows through human food, fodder, fire loss and recycling through residues in winter season crops.

Nitrogen (kg/ha) 160~---------------------------------------------------··----'

"Human food ~ Fodder 1«1 Fire 1055 ~ Residue 140

120 1- ................................. .

1 00 I-w ........................ .

80

60

40

20

o Uni Cai Tui

Paddy Uni Cai Tui

Sorghum Uni Cai

P. millet Uni

P. pea

Fig. 6f. Nitrogen flows through human food, fodder,-frre loss and recycling through residues in rainy season crops.

Plate No.3. Now only few individual frees of Prosopis cineraria are surviving in the irrigated agricultural fields; possibility of increasing agroforestry tree density needs to be explored.