Effect of source and level of sulphur on seed yield and nitrogen and sulphur uptake , by lucerne (Medicago sativa)

A field experiment was conducted to evaluate the efficiency of gypsum and elemental sulphur along with sul- phur levels for seed production of lucerne (Medicago sativa L.) on sandy loam soils during winter seasons of 1998-99, 1999-2000 and 2000-2001. The crop was grown for seed crop after harvesting 2 green forage (GF) cuts. Dry matter (DM) and crude protein (CP) yields were calculated from the GF yield. lncreasing levels of sul- phur from 20 kg to 40 kg Slha significantly increased the seed yield of lucerne. Further, application of sulphur re- sulted in higher DM and CP yields over the control. Treated plot with sulphur showed higher uptake of N by lucerne plants, in total of 2 cuts compared with the control. Application of sulphur increased significantly sulphur uptake by lucerne seed compared with the control. Application of S through gypsum removed higher S by seed lucerne over elemental sulphur. Increasing levels of sulphur from 20 kg to 40 kg Slha increased significantly the S uptake by lucerne seed, but further increase in sulphur level to 60 kg'S1ha significadtly reduced the uptake of S by lucerne seed. These results indicated that 40 kg S/ha was sufficient for the better utilization of nitrogen and sulphur and to obtain higher seed yield and net monetary returns.