Effect of soil physical properties on movement of ³⁵S-tagged Sulphate

The distribution pattern of sulphur after infiltration and redistribution (10 days after infiltration) under varying soil texture, initial soil water content and bulk density was studied using ³⁵S-labeled potassium sulphate (K₂SO₄) and gypsum (CaSO₄.2H₂O) in soil columns. In sandy loam and silty clay loam soils, movement of the labeled sulphur was recorded up to a depth of 20–24 and 16–22 cm in infiltration studies, and 27–30 and 22–28 cm in redistribution studies, respectively. Compared to the sandy loam soil, initial soil water content had a more pronounced effect in silty clay loam soil. However, the effect of bulk density was influenced largely by soil texture, initial soil moisture content, and source of sulphur. Sources exhibited a differential movement of labeled sulphur. Gypsum had two concentration peaks (the primary one being at the surface), whereas K₂SO₄ exhibited only one concentration peak well below the surface. About 55–90% of the applied gypsum and only 11–40% of the applied K₂SO₄ was retained in the top 0–15 cm soil layer.