Effect of weed control and nutrient management on soybean (Glycine max) productivity

A field experiment was conducted at Kota during rainy season of 2002 and 2003 to evaluate the effect of herbicides and their mixtures and of fertility levels on the extent of weed control and productivity of soybean [Glycine max (L.) Merr]. Two hand-weedings at 30 and 45 days after sowing (DAS), alachlor applied pre-emergence @ 2 kg/ha + hand-weeding (HW) at 30 DAS and tank mixture of chlorimuron ethyl + fenoxaprop-p-ethyl (9+70 and 6+50 g/ha) as post-emergence reduced the weed density and dry matter at 50 and 70 DAS. These treatments also recorded significantly higher pods/plant, 1000-seed weight, seed yield and net return of soybean crop. Lowest NPK uptake by weeds was recorded by two hand-weedings and the maximum NPK uptake by the crop under alachlor 2 kg/ha + HW at 30 DAS, two hand weedings and chlorimuron ethyl + fenoxaprop-p-ethyl (9+70 g/ha) treatments. Fertility levels did not influence the weed density, but a decrease in fertilizer application to 75% of recommended dose of fertilizer (RDF) reduced the dry matter of weeds. The yield and net returns decreased on reducing the rate of fertilizer application. No significant influence on NPK uptake by weeds was registered by applying 125% RDF, but nutrient uptake by crop increased significantly.