Row spacing and weed management methods influences growth and yield of soybean (Glycine max (L.) Merr.)

Weed infestation is among the primary reasons for low yields of soybean in Nigeria and other parts of Sub Saharan Africa (SSA). Field trials were therefore carried out in 2016 and 2017 cropping seasons to evaluate the effect of row spacing and weed management methods on growth and yield of soybean. The use of 50 cm row spacing resulted in significant (P < 0.05) reduction in weed cover score, weed density and weed dry matter with subsequent increase in soybean growth and grain yield compared to 75 and 100 cm row spacings in both years. In addition, early weed control with probaben at 2.0 kg a.i (active ingredient) ha¹ followed by (fb) supplementary hoe weeding (shw) at 6 weeks after sowing (WAS) suppressed weeds and increased soybean growth, which carried through to final dry matter and yield. Pre-emergence application of Probaben fb shw at 6 WAS gave the best weed control and resulted in significantly (P < 0.05) higher soybean grain yield compared to two and three hoe weedings or sole application of probaben under 50 and 75 cm inter-row spacing. However, three hoe weedings gave the best weed control and grain yield under 100 cm inter-row spacing. These results suggest that narrow row spacing of 50 cm and weed control by pre-emergence application of probaben fb shw will improve the productivity of soybean. Wide row spacing, however, required longer weed-free period and consequently multiple hoe weeding for optimum soybean yield.