Effect of varieties, crop geometries and weed management on nutrient uptake by soybean (Glycine max) and associated weeds

A field experiment carried out during the rainy season of 2001 and 2002 on clay loam alkaline soil at Udaipur (Rajasthan) showed that soybean [Glycine max (L) Merr.] variety ‘JS 335’ outyielded ‘NRC 37’ and ‘JS 71–05’ in terms of N and P uptake. Crop geometries (30 cm x 10 cm and 20 cm x 15 cm) did not show any significant variation for N and P uptake by crop and associated weeds. All the weed-management treatments significantly reduced removal of N and P by weeds and enhanced uptake of these nutrients by soybean compared to weedy check. Two hand-weedings at 20 and 40 days after sowing and pre-emergence application of clomazone at 1.0 kg/ha + hand-weeding at 40 days were at par and resulted in significant reduction in uptake of N and P by weeds and increase in uptake of these nutrients by soybean compared to all other methods of weed control. Seed and straw yields of soybean were also increased significantly owing to these 2 methods of weed control compared to rest of the methods.