effect of wetting and drying on dtpa‐extractable fe, zn, mn, and cu in soils 1
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Effect of wetting and dryingon DTPA‐extractable Fe, Zn,Mn, and Cu in soilsA. Khan a & P. N. Soltanpour aa Department of Agronomy , Colorado StateUniversity , Fort Collins, Colorado, 80523Published online: 11 Nov 2008.
To cite this article: A. Khan & P. N. Soltanpour (1978) Effect of wetting anddrying on DTPA‐extractable Fe, Zn, Mn, and Cu in soils , Communications in SoilScience and Plant Analysis, 9:3, 193-202, DOI: 10.1080/00103627809366800
To link to this article: http://dx.doi.org/10.1080/00103627809366800
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COMMUN. IN SOIL SCIENCE AND PLANT ANALYSIS, 9(3), 193-202 (1978)
EFFECT OF WETTING AND DRYING ON DTPA-EXTRACTABLE
FE, ZN, MN, AND CU IN SOILS1
KEY WORDS: Micronutrients, soil testing
A. Khan and P. N. Soltanpour2
Department of AgronomyColorado State University
Fort Collins, Colorado 80523
ABSTRACT
The study reported herein was intended to determine the ef-
fect of (i) wet-incubation and subsequent air-drying, and (ii)
oven-drying on DTPA-Fe, Zn, Mn, and Cu.
Analysis of wet-incubated soils showed significant decreases
in DTPA-Fe, Mn, and Cu at the 1% and Zn at the 10% level of proba-
bility. Air-drying of these moist-incubated soils increased the
levels of Fe, Zn, and Cu to values close to their original levels.
Levels of Mn sharply deviated from their original values after air-
drying of incubated soils. Correlation coefficients (r) between
the amounts of extractable nutrients in original air-dry soils
and wet-incubated soils were 0.54, 0.87, 0.91, and 0.13 for Fe,
Zn, Cu, and Mn, respectively. Oven-drying increased the levels of
DTPA-extractable micronutrients from 2 to 6 fold.
193
Copyright © 1978 by Marcel Dekker, Inc. All Rights Reserved. Neither this work nor any partmay be reproduced or transmitted in any form or by any means, electronic or mechanical, includingphotocopying, microfilming, and recording, or by any information storage and retrieval system,without permission in writing from the publisher.
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194 KHAN AND SOLTANPOUR
INTRODUCTION
Many soil testing laboratories in the Western USA use the DTPA
test to assess the availability of Zn and Fe and to a limited ex-
tent Cu and Mn. With respect to sample handling, it is generally
recommended that soil samples be air-dried as soon as possible,
after they are obtained from a field. However, moist samples are
sometimes submitted to the soil testing laboratories, and a week
or more may pass before these samples are air-dried for analyses.
The effect of wet-incubation and air-drying after wet-incubation
on DTPA-extractable micronutrients in the soil is unknown.A
Elgala and Maier reported a decrease in EDTA-extractable Fe
in soils kept at high moisture levels compared to low. The de-
crease in Fe was attributed to a relative increase in Ca under
the most moist condition. Increase in the amount of exchangeable
Mn following air-drying has been reported, and it was proposed
that available Mn should be determined in moist soil samples .
The objectives of the study reported herein were to determine
the effect of (i) wet-incubation and subsequent air-drying, and
(ii) oven-drying on DTPA extractable Fe, Zn, Mn, and Cu.
MATERIALS AND METHODS
Twenty-four soils from Colorado farms, with a wide range in
texture and relatively low levels of Fe and Zn (soils 5 to 28),
were used for the 1st part of this study (Table 1). These soils
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DTPA-EXTRACTABLE Fe, Zn, Mn, AND Cu 195
TABLE 1
Some Properties of Soils Used In This Study
Soil No.
12345678910111213141516171819202122232425262728
Texture
Sandy loamClay loamSilty clay loamLoamLoamy sandSandy loamLoamy sandSilty clay loamSilty clay loamClay loamLoamy sandClay loamSandy clay loamSandy clay loamSilty clay loamSilty clay loamSilty clay loamLoamy sandSandy loamSilty clay loamSilty clay loamLoamy sandClay loamSandy loamSandy clay loamSandy clay loamLoamy sandLoamy sand
Organic matter
%
0.81.41.61.20.70.60.60.91.03.00.61.41.11.01.81.61.80.71.71.21.70.52.01.01.71.40.30.4
PH
7.88.07.28.47.67.37.48.17.97.88.17.88.07.97.87.57.48.47.87.79.28.78.18.08.17.78.98.4
were analyzed for DTPA-extractable Fe, Zn, Mn, and Cu after air-
drying, grinding with a wooden roller, and passing through a 2-mm
stainless steel sieve ' . Fifty gram soil samples were placed
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196 KHAN AND SOLTANPOUR
in 250 ml Erlenmeyer flasks and then brought to 1/3 bar moisture
tension with demineralized water. The flasks were covered with
parafilm, and kept for one week at room temperature. Subse-
quently Fe, Zn, Mn, and Cu were determined in moist soil samples.
A subsample obtained from each moist soil sample was air-dried
and ground with a wooden roller to pass through a 2-mm stainless
steel sieve before determination of micronutrients.
The effect of oven-drying was evaluated using soils 1, 2,
3, and 4 (Table 1). The soils were analyzed before and after
oven-drying at 110°C for 48 hours.
RESULTS AND DISCUSSION
Incubation of moist soils caused a decrease in Fe, Mn, and
Cu levels in 23 out of 24 soils (Table 2). Using each soil as
a replicate, the mean decrease was statistically significant at
the 1% level for these three elements. The levels of zinc de-
creased as a result of incubation in 20 out of 24 soils. The
mean decrease for Zn was statistically significant at the 10%
level. Air-drying of incubated soils increased the levels of Fe,
Zn, and Cu to values close to their original levels; however, Mn
levels on the average were lower than the original levels. The
decrease in micronutrient availability associated with high mois-
ture levels has been observed through chlorosis of plants in
calcareous soils at different parts of the world4' 7) 8> 9> 10.
The incidence of chlorosis was associated with the production of
high levels of bicarbonate ions under wet conditions11' 12. The
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DTPA-EXTRACTABLE Fe, Zn, Mn, AND Cu 197
TABLE 2
Effect Of Wetting And Drying On DTPA-ExtractableMicronutrients
a.
SampleNn
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
X
Iron and
1
5.2
6.0
4.7
3.0
2.9
3.7
5.9
4.0
3.3
3.7
7.3
8.7
6.7
4.3
6.6
3.5
4.5
2.7
3.6
5.9
3.4
5.3
5.2
6.0
4.9a
Zn
Fe2
2.13.8
2.2
1.0
0.8
1.7
2.7
1.4
1.2
1.2
2.5
2.9
1.9
2.4
2.1
1.0
2.4
1.5
4.2
2.7
1.3
1.7
3.0
3.0
2.1b
3
5.
5.
4.
3.
2.
3.
5.
3.
2.
3.
7.
8.
5.
4.
7.
5.
7.
2.
3.
6.
4.
5.
5.
6.
5.
. . • HI-"08
1
4
8
6
4
6
9
0
6
6
9
9
40
9
9
8
2
5
4,8
.3
,1a
1
3.360.130.390.130.25
0.441.37
6.920.60
0.350.450.16
4.440.450.370.77
0.320.140.34
0.380.410.320.260.961.01a
Zn2
2.400.200.420.200.220.53
0.66
2.150.40
0.28
0.240.11
1.010.310.220.30
0.260.100.25
0.230.240.24
0.260.550.49a
3
2.980.180.410.22
0.330.55
1.15
3.500.71
0.430.540.38
2.070.640.54
0.911.570.230.40
0.480.520.390.35
0.830.85a
1 Original air-dry2 Soil incubated for 7 days at 1/3 bar moisture tension and
analyzed wet.3 Soil air-dried after 7 days of incubation
(continued...)
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198 KHAN AND SOLTANPOUR
TABLE 2. CONTINUED
b. Manganese and Cu
SampleNo.
5
6
7
8
9
10
1112131415161718192021
2223
2425262728
X
19.9
10.6
10.0
9.711.7
9.9
2.65.54.04.55.2
8.8
7.7
2.9
3.9
5.8
3.0
2.6
3.3
3.6
4.74.97.12.2
6.0a
Mn11.9
2.91.9
1.3
1.3
1.4
0.9
1.11.31.11.02.31.32.41.61.22.6
1.5
0.9
2.0
2.0
2.0
7.11.61.9b
. —.. .ppm.3i7 ^4.13.7
2.3
2.5
3.2
2.3
2.8
2.8
2.7
2.75.13.6
4.24.77.5
5.0
3.5
3.0
4.78.15.210.8
3.24.4c
10.66
0.54
0.26
1.00
0.92
0.81
0.31
0.45
0.33
0.33
0.78
1.41
1.80
0.27
0.88
0.80
0.88
0.47
0.62
1.11
0.74
1.12
0.51
0.49
0.73a
Cu2.0.42
0.41
0.21
0.71
0.58
0.55
0.18
0.49
0.29
0.22
0.43
0.72
0.78
0.24
0.51
0.41
0.41
0.35
0.35
0.66
0.41
0.66
0.41
0.33
0.45b
3.
6.610.47
0.24
0.95
0.84
0.68
0.37
0.55
0.35
0.34
0.79
1.35
1.35
0.35
0.93
0.89
0.83
0.51
0.65
1.15
0.81
1.23
0.65
0.59
0.73a1 Original air-dry2 Soil incubated for 7 days at 1/3 bar moisture tension and
analyzed wet.3 Soil air-dried after 7 days of incubation
*Figures under the same element followed by the same letter are notsignificantly different at the 1% level.
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DTPA-EXTRACTABLE Fe, Zn, Mn, AND Cu 199
data reported here, however, suggests that high moisture lowers
the micronutrient availability in the soil and this may be the
reason for chlorosis observed under these conditions.
Correlation coefficients for these 4 elements among values
obtained from (1) original air-dry soils, (2) soils incubated
at 1/3 bar moisture tension, and (3) those air-dried following
incubation, are given in Table 3.
The correlation co-efficients (r) for Fe, Zn, and Cu were
significant at the \% level, and those for Mn were not significant.
Analysis of dry soil did not reflect Mn status of these soils at
1/3 bar moisture tension. Sherman and Harmer proposed that soils
should be analyzed for Mn in their field moist conditions. The
correlation coefficient for Fe between original air-dry soils and
TABLE 3
Correlation Matrices for Fe, Zn, Mn, and Cu.
Fe Zn Mn Cu
2
3
1
0.54**
0.86**
1
0.87**
0.92**
1
0.13
-0.04
1
0.91**
0.95**
1) Original Air-dry
2) Soil incubated for 7 days at 1/3 bar moisture tension andanalyzed wet.
3) Soil air-dried after 7 days of incubation.**
Values were significant at the 1% level.
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200 KHAN AND S0LTANP0UR
those incubated at 1/3 bar tension was significant, but small.
However, more research is needed to determine effect of different
moisture levels and drying and wetting cycles on extractable
levels of Mn and Fe.
The superiority of one method of extraction over the other
for Mn and Fe should be established by further research. Zinc
and Cu levels in moist and dry soils are highly correlated and the
soils could be analyzed wet or dry for determining availability
indices of these elements.
Pven-drying increased the DTPA-extractable levels of Fe, Zn,
Mn, and Cu from 2 to 6 fold (Table 4). This may be due to re-
lease of these elements from organic matter.
TABLE 4
The Effect Of Pven-Drying On PTPA-Extractable Fe, Zn, Mn and Cu.
SoilNo.
1
3
4
5
X
Air-dry
4.1
2.8
3.1
2.9
3.2a*
FeOven-dry
16.3
15.3
19.5
15.1
15.8b
A.P.
0.60
0.20
0.30
0.50
0.40a
Zn0.0.
ppm - -
0.97
0.58
0.86
1.03
0.86b
MnA.O.
5.0
11.4
14.0
6.2
9.2a
O.P.
17.1
21.1
32.6
27.9
24.7b
CuA.P.
0.38
0.34
0.37
0.37
0.37a
O.P.
0.73
0.88
0.93
0.87
0.85b
*
Figures under the same element followed by different letters are
significantly different at the 1% level.
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DTPA-EXTRACTABLE Fe, Zn, Mn, AND Cu 201
SUMMARY AND CONCLUSIONS
The results and conclusions based on the work reported here
are:
(1) Soils may be analyzed in wet or dry conditions for Zn
and Cu. However, critical levels used should reflect
the moisture condition of the soil.
(2) Manganese availability index of wet soils is not corre-
lated with that of respective dry soils. For Fe there
is significant correlation between wet and dry availa-
bility indices; however, the correlation coefficient
value is small (0.54). Superiority of one method over
another for these elements should be established.
(3) Solubility of micronutrients decreases upon incubation
of moist soils. This phenomenon may explain the fre-
quent occurrence of chlorosis under conditions of in-
creased moisture levels.
(4) Oven-drying increases the DTPA-extractable levels of
Fe, Zn, Mn, and Cu to a large extent.
REFERENCES
1. Published as scientific series paper No. 2283.
2. Graduate Assistant and Associate Professor, Department ofAgronomy, Colorado State University, Fort Collins, Colorado.
3. Lindsay, W. L. and W. A. Norvell. 1969. Development of aDTPA micronutrient test. Agron. Abstr. p. 84.
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202 KHAN AND SOLTANPOUU
4. Elgaia, A.M., and R.H. Maier. 1964. Chemical forms of plantand soil Fe as influenced by soil moisture. Plant Soil.21:201-212.
5. Sherman, G.D. and P.M. Harmer. 1942. The manganese-manganicequilibrium of soils. Soil Sci. Soc. Amer. Proc. 7: 398-405.
6. Soltanpour, P.N., A. Khan, and W. L. Lindsay. 1976. Factorsaffecting DTPA-extractable Fe, Zn, Mn, and Cu from soils.Comm. Soil Sci. Plant Anal. 7(9): 797-821.
7. Olomn, M.O. and G.J. Racz. 1974. Effect of soil water andaeration on Fe and Mn utilization by flax. Agron. J. 66:523-526.
8. Ryan, P., J. Lee, and T.F. Peebles. 1967. Trace elementsproblem in relation to soil units in Europe. Food, and Agri-culture Organization of United Nations. World Soil Resourcesreport #31.
9. Tarania, L.F. 1973. Changes in the redox potential andavailable Fe content during the flooding and subsequent dry-ing of grey forest soil. Abstracted in Soils Fert. 37:(791), 1974.
10. Wallace, A., E.M. Romney, and G.W. Alexander. 1976. Limeinduced chlorosis caused by excess irrigation water. Commun.Soil Sci. Plant Anal. 7 (1): 47-49.
11. Boxama, R. 1972. Bicarbonate as the most important soilfactor in lime induced chlorosis in Netherlands. Plant Soil.37: 233-243.
12. Lindsay, W.L. and D.W. Thorne. 1954. Bicarbonate ion andoxygen level as related to chlorosis. Soil Sci. 77:271-279.
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