Studies on S Nutrition of Soybean (Glycine max L.) from Three Sulphate Sources

In a pot experiment conducted on soybean with 4 levels of S (0, 5,10 and 20 ppm) supplied through ₃₆S tagged CaSO₄,2H₂O, (NH₄)₂SO₄ and Na₂SO₄, it was observed that S application increased the yield of dry matter, total S removal, sulphate-S, protein-S and non-protein organic-S content in plant but a decline in each plant attribute was found in case of Na₂SO₄ at higher levels of S application. Radio-assay indicated that at lower doses of applied S, relatively more fertilizer S was metabolised to protein formation and less at higher doses. Sulphur in plant derived from fertilizer increased but per cent utilization of applied S decreased with increasing dose of sulphur. Calcium sulphate was the superior source as per cent uptake and per cent utilization of applied S was the highest in this case. Ammonium sulphate was relatively better when dry matter yield production was taken into account and it also increased the utilization of S from soli source