Effects of Weed-free Period on Seed Yield and Yield Components of Double-cropped Soybean (Glycine max L.)

Maintaining weed-free period longer than required for optimum seed yield increases cost of crop production. A two-year study was conducted to determine the critical weed-free period for double-cropped soybean to obtain maximum seed yield. The experimental design was Randomized Complete Blocks with three replications. Seed yield varied between 1289.3 and 4778.3 kg ha-1 in 2002 and between 1007.3 and 3980.0 kg ha-1 in 2003. The highest and the lowest seed yield were obtained from weed-free and weedy control treatments, respectively in both years. Seed yield exponentially increased with the increasing weed-free period in 2002 and 2003. Seed yield increase in increased period of weed-free plots was resulted from increased pod and seed number/plant. The result of present study showed that double-cropped soybean must be kept weed-free from emergence till physiological maturity to obtain maximum seed yield.