Critical concentration of sulphur in urdbean

A pot experiment was conducted during kharif 2006 using purified silica sand to study the effect of sulphur nutrition on urdbean (Vigna mungo L. Hepper). There were 6 treatments of sulphur viz., 0, 0.05, 0.1, 0.2, 0.5, 2.0 and 5.0 mM added in the form of K2SO4. Sulphur content and the dry matter yield at various growth stages were plotted and the polynomial regression equation was derived and critical concentration of sulphur was determined. Increase in level of sulphur up to 0.2 mM resulted in significant increase of sulphur in plants and the values almost plateaued thereafter. Higher rate of accumulation of sulphur was noticed in 4^th leaf from top as compared to 2^nd and 6^th leaves. Critical concentration of sulphur in urdbean ranged from 0.10 to 0.21 per cent at different growth stages. The per cent yield predictability was maximum for 4th leaf at 45 DAS (R²= 0.95).