Influence of row spacing and weed control methods on weed population dynamics in soybean (Glycine maxL.)

Weed infestation is a major factor attributed for the poor yield of soybean. Field experiments were therefore conducted to evaluate the influence of row spacing and weed control methods on weed dynamics, seed yield and profitability of soybean. The use of 50 cm row spacing reduced the density and biomass of grass weed species includingDigitaria horizontalis,Panicum maximum,Cynodon dactylonandPaspalum scrobiculatumwith subsequently higher soybean dry matter, seed yield, revenue and marginal returns compared to 75 and 100 cm row spacing. However, some broad-leaved weed species likeCommelina benghalensis,Gomphrena celosioidesandAmaranthus spinosuswere not controlled at 50 compared to 75 and 100 cm row spacing. Regardless of row spacing, herbicide (butachlor) application plus hoe weeding reduced total weed density and biomass with subsequently higher soybean dry matter, seed yield, revenue and marginal returns than two hoe weedings or sole herbicide application. The result suggests that narrow row spacing of 50 cm and integrated weed control by butachlor plus hoe weeding will improve weed control efficiency, productivity and profitability of soybean.