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 sulphur 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. Increasing levels of sulphur from 20 kg to 40 kg S/ha significantly increased the seed yield of lucerne. Further, application of sulphur resulted 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 S/ha increased significantly the S uptake by lucerne seed, but further increase in sulphur level to 60 kg S/ha significantly 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.