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Study of the Isotopic Exchange Behaviour of Sulphate in Soil as Related to Equilibrium Concentration

FARRUKH AHMED
Atomic Energy Centre, Dacca

MESBAHUL KARIM
Atomic Energy Centre, Dacca

AMINUL ISLAM
Soil Science Deptt., Dacca University, Dacca.

Abstract/ Executive Summary:

Several workers have indicated a correlation between exchangeable phosphorus and plant available phosphorus, others were unable to obtain such a correlation. One of the causes of this discrepancy is the fact that the exchangeable phosphorus measurements are limited by the accuracy of such measurements. Fathi Amer (1962) and Russell (l954) after extensive studies recommended methods for determining the isotopically exchangeable phosphorus at a definite solution concentration and a definite period of shaking. No information regarding solution concentration and time of shaking in deter-mining isotopically exchangeable sulphate is available. Subbiah et al. (1965) determined isotopicallv exchangeable sulphate using the method recommended by Russell (1954) for phosphorus. The objective of the study was therefore, to assess a suitable solution concentration at which isotopically exchangeable sulphate can be determined for different types of soil. The results suggest that for anyone type of soil, solution concentration greater than 10 ppm S is most unsuitable and the sensitivity of the method is greatly affected. Further detailed works should be carried out before a definite solution concentration in the low level (less than 10 ppm S) may be suggested.

Keywords: Suitable solution, Isotopically exchangeable sulphate, Soils

Location: Atomic Energy Centre, Dacca

Start Date:

End Date:

Program Area: Crop-Soil-Water Management

Commodity: Soil fertility

Objectives:

The object of this study was to assess a suitable solution concentration at which isotopically exchangeable sulphate can be-determined for different types of soils of varying characteristics.

Methodology:

Soil samples representing surface soils of 0"-6" depth were collected from several places covering seven soil tracts of East Pakistan. The soils were air dried, ground and screened through 0.5 mm. sieve and analysed for chemical composition and mechanical fractions. The isotopic exchange studies were done on mine soil types with concentrations varying from 2 to 500 ppm S tagged with S and the shaking time being half an hour. After centrifuging the final activities were determined according to the method outlined by Chao et. al. (1962) where 1 ml. of clear solution were pipette into a stainless steel planchet. After drying by the help of an infrared lamp, the radioactivity was measured with an autoscaler and G.M. Thin Mica window (1.8mg/cm²) counter. The concentration of sulphate was determined chemically using the turbidimetric method of Chesmin and Yien (1951). The initial and final activities of the solution and their concentrations for sulphur were recorded for calculation of isotopically exchangeable ions. Determination of isotopically exchangeable sulphur is based on the thesis that addition of S to a soil-water system will react according to the following equation and after equilibrium the specific activity of the sulphate will be uniform through out the system. S solution+S soil-S soil + S solution.

Source of Information: Pak.J. Soil Sci. 4(2) 1-7.1968

Article Link (Online Journal):

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

The results suggest that for anyone type of soil, solution concentration greater than 10 ppm S is most unsuitable and the sensitivity of the method is greatly affected.

Knowledge Management: Journal