Adynamic equilibrium exists between the adsorbed

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1 The An Asian Journal J.of Hort. of June Soil Science, 2008 Vol. (December 3 (1) : (...) 2009 to May-2010) Vol. No. 2 : Research Paper : Effect of lime on the changes in adsorbed and soluble sulphate in Alfisols of Orissa Accepted : October, 2009 See end of the article for authors affiliations Correspondence to : P.K. DAS Department of Soil Science and Agricultural Chemistry, Orissa University of Agriculture and Technology, BHUBANESWAR (ORISSA) INDIA ABSTRACT A laboratory investigation was carried out to study the effect of lime applied with and without gypsum on the changes in adsorbed and soluble at different time intervals in two Alfisols of Orissa. Lime was 0 and 0.3 LR with three different combinations of sulphur i.e. 0, 20 and 0 µg g -1 through gypsum. The soils were incubated for a period of 60 days. Soil ph, after liming, increased by 0.3 to 0.6 unit in Dhenkanal soil and 0. to 0.9 unit in Jharsuguda soil at different days of the incubation period in different treatments. Soil ph either remained constant or decreased slightly with application of gypsum. There was a significant reduction in exchangeable H + and Al +++ after liming. Effect of gypsum on the changes in exchangeable H + and Al +++ was insignificant. Application of lime decreased the adsorbed -S by 20.3 to 58.1 % and 30.9 to 7.5 % and increased the soluble by 1.3 to 99.3% and 21.3 to 125.% in Dhenkanal and Jharsuguda soils, respectively in different treatments at different days of the incubation period. However, adsorbed, soluble and (adsorbed + soluble) were higher in the lime + gypsum treated soils than in the lime treated soils only. There were irregular changes in adsorbed, soluble and (adsorbed + soluble) with increasing days of the incubation period. Key words : Alfisol, Lime, Gypsum, Soil ph, Adsorbed -S, Soluble Adynamic equilibrium exists between the adsorbed and soluble sulphate in soil which controls the sulphate availability to plant. With removal of sulphate from the soil solution due to plant uptake, the adsorbed sulphate is released to the soil solution to maintain the equilibrium and the reverse occurs with addition of sulphate to the soil solution. Sulphate adsorption by soil is highly ph dependent. It decreases with increasing ph since the OH is a strong competitor of to occupy the adsorption sites (Huang et al., 1998). More than 70 % of the cultivated area in Orissa is covered by Alfisols. These soils are moderately to strongly acidic with high Fe and Al oxides and are dominated by low active clays (Das, 1985).Soil acidity is the major constraint for crop production in these soils. These soils, therefore, need liming to correct soil acidity for increasing crop production. The effect of lime persists only for a short period due to heavy precipitation causing the loss of Ca from soil. The present recommendation is, therefore, application of lime at a lower rate i.e. 0.2 to 0.3 LR to each crop or to alternate crop (depending upon the reduction in ph) before sowing or planting. No information is available on the effect of lime on the changes in adsorbed and soluble in these soils at different time intervals when applied at a lower rate with and without gypsum. The present communication reports the effect of lime 0.3 LR with and without gypsum on the changes in adsorbed and soluble -S at different time intervals in two Alfisols of Orissa. MATERIALS AND METHODS Surface soil samples (0-15 cm) were collected from the upland cultivated areas of two acid soils viz., Dhenkanal and Jharsuguda belonging to Alfisols. The soils were air-dried, ground and passed through 2 mm sieve. Some of the important physical and chemical properties of the soils were determined by standard procedures. Exchangeable H + and Al +++ were determined in 1 M KCl extract of soil (Black, 1965). Lime requirement of these soils to ph 7.0 was determined by Woodruff s buffer method. Soluble -S was extracted by 0.15 % CaCl 2.2H 2 O (Tabatabai, 1982), whereas (adsorbed + soluble) was extracted by Ca(H 2 PO ) 2 solution containing 500 ppm P (Ensminger, 195). Sulphate -S in these extracts were determined turbidimetrically (Hoeft et al., 1973). For the incubation study, 250 g of soils, passed through 2 mm sieve, were taken in 500 ml polythene beakers in duplicate. Required quanties of pure CaCO 0 and 0.3 LR were added to the soils and mixed thoroughly. Required quantities of pure Ca. 2H 2 O to supply 0,20 and 0 µg g -1 were dissolved in the volume of water needed to maintain the field capacity of soil. The solutions

2 319 were, then, added to both limed and unlimed soils in the polythene beakers. The weights of the polythene beakers containing the moist soils were then recorded. The beakers were covered with perforated polythene sheets. Weights of the beakers were checked at every 3 days interval and the loss of moisture was compensated by adding equal volume of distilled water. Soil samples were drawn at 15,30,5 and 60 days of the incubation period and analysed for ph, soluble, (adsorbed + soluble) after making necessary corrections for moisture contents. Exchangeable H + and Al +++ were determined in the soil samples drawn at 60 days of the incubation period. RESULTS AND DISCUSSION Some of the important physical and chemical properties of the soils are presented in Table 1. The Dhenkanal soil was sandy loam in texture with ph.7,whereas Jharsuguda soil was clay in texture with ph 5.3.Both the soils were low in organic carbon content. Lime requirement of the Jharsuguda soil was greater than that of the Dhenkanal soil although the ph of the Jharsuguda soil was greater than that of the Dhenkanal soil. This might be due to greater buffering capacity of the Jharsuguda soil because of its higher clay content than of the Dhenkanal soil. Table 1 : Some important physical and chemical properties of the soils Dhenkanal Jharsuguda Soil properties soil soil Texture Sandy Clay loam Clay (%) ph (1:2.5) EC (ds m -1 ) Org. C (%) Exchange acidity [cmol(p + )kg -1 ] Exchangeable H + [cmol(p + )kg -1 ] Exchangeable Al +++ [cmol(p + )kg -1 ] Lime requirement (kg CaCO 3 ha -1 ) Soluble S ( g g -1 ) Adsorbed SO 2 SO 2 S ( g g -1 ) Changes in soil ph after liming: Liming the soils at 0.3 LR increased the ph by 0.3 to 0.6 unit in Dhenkanal soil and 0. to 0.9 unit in Jharsuguda soil at different days of the incubation period in different treatments (Table 2).The less increase in ph in Dhenkanal soil than in Jharsuguda soil might be due to greater exchangeable Al +++ content in Dhenkanal soil than in Jharsuguda soil. Table 2 : Changes in soil ph (1 : 2.5) after application of lime with and without gypsum SO 2 S Dhenkanal Soil Jharsuguda Soil added ( g g -1 ) 0 LR 0.3 LR ph 0 LR 0.3 LR ph (15 days) days days days Changes in soil ph with application of gypsum: Application of sulphur through gypsum in both limed and unlimed soils did not cause a significant reduction in soil ph. The decrease in ph with application of gypsum varied from 0 to 0.3 unit in the unlimed and 0.1 to 0.2 unit in the limed soils of Dhenkanal at different days of the incubation period. It varied from 0 to 0.1 unit in both unlimed and limed soils of Jharsuguda at different days of the incubation period. A decrease of 0.6 unit ph was only observed in the limed soil of Jharsuguda in the 15th day of incubation at the level of 0 µg g -1 of -S added which was an exceptional case. The insignificant reduction in ph might be due to addition of gypsum in very small quantity as a source of nutrient only. Changes in soil ph with incubation period : No significant change in soil ph was observed with increasing days of the incubation period in different treatments in both Dhenkanal and Jharsuguda soils. Soil ph in Dhenkanal soil at 60 days of the incubation period was only 0.1 to 0.3 unit less in the unlimed soils and 0 to 0.2 unit less in the limed soils than the corresponding ph values at 15 days of the incubation period. In Jharsuguda soil, the ph at 60 days of the incubation period was only 0.1 to 0.2 unit less in the unlimed soils and 0.2 unit less in the limed soils than the corresponding ph values at 15 days of the incubation period. These observations showed that the equilibrium between active and reserve acidity has been attained within 15 days of application of lime in both Dhenkanal and Jharsuguda soils. In the unlimed soils

3 EFFECT OF LIME ON ADSORBED & SOLUBLE SULPHATE IN ALFISOLS 320 of Dhenkanal and Jharsuguda, the equilibrium between active and exchange acidity remained almost stable throughout the incubation period, with minor fluctuations. Changes in exchangeable H + and Al +++ in the soils after liming : Liming decreased the exchangeable H + and Al +++ contents measured at 60 days of the incubation period in both Dhenkanal and Jharsuguda soils (Table 3). Exchangeable H + content decreased to 0.15 to 0.22 cmol (p + ) kg -1 from its initial value of 0.36 cmol(p + )kg -1 in Dhenkanal soil and was undetectable in Jharsuguda soil having the initial exchangeable H + content of 0.29 cmol(p + )kg -1. Exchangeable Al +++ content in Dhenkanal soil decreased to 0.12 to 0.1 cmol(p + ) kg -1 from its initial value of 0.62 cmol(p + )kg -1 and was undetectable in Jharsuguda soil having the initial exchangeable Al +++ content of 0.08 cmol(p + ) kg -1. The decrease in Table 3 : Changes in exchangeable H + and Al +++ in the soils due to liming at 60 days of the incubation period Exchangeable H + Exchangeable Al SO cmol(p + )kg -1 cmol(p + )kg -1 ( g g -1 ) 0 LR 0.3 LR 0 LR 0.3 LR Dhenkanal soil Jharsuguda soil ND 0.12 ND ND 0.1 ND ND 0.10 ND exchangeable H + was because of its neutralization by the added lime, whereas the decrease in exchangeable Al +++ was due to its inactivation by OH - with increase in ph after liming. In the unlimed soils of Dhenkanal, there was slight increase in exchangeable H + and a slight decrease in exchangeable Al +++ at 60 days of the incubation period. In the unlimed soils of Jharsuguda there was slight decrease in exchangeable H + and increase in exchangeable Al +++ at 60 days of the incubation period. Changes in exchangeable H + and Al +++ in the soils with application of gypsum : No significant change in exchangeable H + and Al +++ was noticed at 60 days of the incubation period with increasing levels of S added through gypsum in both unlimed and limed soils of Dhenkanal and Jharsuguda as compared to zero sulphur application. Effect of the added -S on the adsorbed and soluble -S in soil : Both adsorbed and soluble -S increased with addition of -S in soil (Table and 5). A dynamic equilibrium exists between the adsorbed and soluble -S in soil. With addition of -S to soil, concentration of in the soil solution increases and the rate of -S adsorption by soil also increases. A part of the added -S, therefore, get adsorbed and the rest remain in the soil solution increasing both adsorbed and soluble -S in soil. Both adsorbed and soluble -S were higher at the level of 0 µg g -1 of -S added than at Table : Changes in soluble and adsorbed -S after liming at different incubation periods in Dhenkanal soil Soluble SO 2 S ( g g -1 ) Adsorbed SO 2 S ( g g -1 ) (Soluble +Adsorbed) SO 2 SO 2 S ( g g -1 ) ( g g -1 ) 0 LR 0.3 LR % Increase 0 LR 0.3 LR % Increase 0 LR 0.3 LR % Increase 15 Days Days Days Days

4 321 Table 5 : Changes in soluble and adsorbed SO -S after liming at different incubation periods in Jharsuguda soil Soluble SO 2 S ( g g -1 ) Adsorbed SO 2 S ( g g -1 ) (Soluble +Adsorbed) SO 2 SO 2 S ( g g -1 ) ( g g -1 ) 0 LR 0.3 LR % Increase 0 LR 0.3 LR % Increase 0 LR 0.3 LR % Increase 15 Days Days Days Days the level of 20 µg g -1 of -S added. This was due to increasing rates of adsorption as well as desorption of with increasing levels of -S added. There was an increase in (adsorbed+ soluble) -S with increasing levels of -S added which was due to increase in both the forms of sulphur with increasing levels of -S added. Changes in the adsorbed and soluble in the soils after liming : Liming decreased the adsorbed -S and increased the soluble -S in both the soils. Adsorbed -S decreased by 20.3 to 58.1% in Dhenkanal soil and 30.9 to 7.5% in Jharsuguda soil, whereas soluble increased by 1.3 to 99.3% in Dhenkanal soil and 21.3 to 125.% in Jharsuguda soil at different days of the incubation period in different treatments after liming. Liming increases the OH - concentration in the soil solution. In the treatments receiving no sulphur, decrease in adsorbed -S and increase in the soluble -S after liming might be due to replacement of the adsorbed by the OH - to the soil solution. In the treatments receiving sulphur, the increase in soluble -S and decrease in adsorbed -S after liming might be due to competition of the added -S with OH - to occupy the adsorption sites. Since OH - is a strong competitor of -S, less of the added -S could occupy the adsorption sites and more exist in the soil solution. At a given level of -S added, soluble -S was, therefore, more and adsorbed -S was less in the limed soils than in the unlimed soils. Similar results have been reported by Das et al. (200) in some acid soils of Orissa belonging to Alfisols. Marsh et al. (1987) reported that the decrease in -S adsorption after liming is due to decrease in the surface positive charge and increase in the surface negative charge potential of soil. Sulphate- S in the soil solution are, therefore, subjected to greater repulsion to reach the soil collidal surface and get adsorbed. There were irregular changes in adsorbed and soluble during the incubation period in both limed and unlimed soils of Dhenkanal and Jharsuguda. This might be due to mineralization of organic sulphur or immobilization of during the incubation period, replacement of the adsorbed by different inorganic or organic anions released during the incubation period or the proceed of equilibrium between the adsorbed and soluble after disturbance of the equilibrium. There was an increase in (adsorbed + soluble) after liming varying from 7. to 21.8% in Dhenkanal soil and 1.9 to 5.7% in Jharsuguda soil at 15 days of incubation. This increase might be due to mineralization of some organic sulphur after liming. Marschner (1993) reported that the increase in soluble after liming is due to mineralization of organic sulphur due to enhanced microbial activity. The irregular change in (adsorbed + soluble) -S after 15 days of the incubation period might be due to mineralization of sulphur or immobilization of -S.

5 EFFECT OF LIME ON ADSORBED & SOLUBLE SULPHATE IN ALFISOLS 322 Authors affiliations: D. JENA, B.JENA AND B. MOHANTY, Department of Soil Science and Agricultural Chemistry, Orissa University of Agriculture and Technology, BHUBANESWAR (ORISSA) INDIA REFERENCES Black, C.A. (1965). Methods of Soil Analysis Part 2., American Society of Agronomy, Madison, Wisconsin, USA. Das, P.K. (1985). Characterization of some upland red and lateritic soils of Orissa having low active clay. M.Sc. Thesis, Orissa University of Agriculture and Technology, Bhubaneswar. Das, P.K., Sahu, S.K. and Sarangi, D. (200). Effect of ph and lime on sulphate adsorption in some Alfisols of Orissa. J. Indian Soc. Soil Sci., 5 : Ensminger, L.E. (195). Some factors affecting the adsorption of sulphate by Alabama soils. Soil Sci. Soc. American Proc., 18 (2) : Hoeft, R.G., Walsh, L.M. and Keeney, D.R. (1973). Evaluation of varius extractants for available soil sulphur. Soil Sci. Soc. American Proc. 37 (3) : Huang Jen Tzn, King HengBiao and Wang MingKuang (1998). Sulphate adsorption and desorption of forest soils in Taiwan (1) : Relationship between sulphate adsorption and soil properties and mechanism of sulphate adsorption. J. Chinese Agric. Chemical Soc., 36 (3) : Marschner, B. (1993). Microbial contribution to sulphate mobilization after liming an acid forest soil. J. Soil Sci., (3) : Marsh, K.B., Tillman, R.W. and Syers, J. K. (1987). Charge relationship of sulphate sorption by soils. Soil Sci. Soc. American J., 51 : Tabatabai, M.A. (1982). Sulphur. In : Methods of Soil Analysis, Part 2, 2nd Edn. (Eds. A.L. Page,et al.) : Soil Science Society of America, Madison, Wisconsin, USA. ******** ****** ****