Effect of Planting Date on the Growth and Yield of Soybean in Kwara State

This study examines the effect of different planting dates on the growth performance and grain yield of soybean in Kwara State, North Central Nigeria. Planting date is a critical agronomic management decision that determines the degree of alignment between crop growth stages and seasonal rainfall distribution, temperature regime, and solar radiation availability. In Kwara State's single rainfall season environment, early planting captures peak rainfall during vegetative growth while late planting risks drought stress during flowering and pod filling. This study establishes a randomised complete block design experiment at the University of Ilorin research farm, testing four planting dates: 15 June, 30 June, 15 July, and 30 July, using improved soybean variety TGX1835-10E. Plant height, days to flowering, days to maturity, number of pods per plant, hundred-seed weight, and grain yield are recorded. Findings reveal that the 30 June planting date achieves the highest grain yield of 2.4 tonnes per hectare, coinciding with peak vegetative growth during maximum rainfall and pod fill during the tapering rainfall period which reduces disease pressure. The 15 June planting produces slightly lower yield due to early season dry spell impacts on seedling establishment. Planting on 30 July results in severe drought stress during reproductive stages, reducing yield to 1.1 tonnes per hectare. The study concludes that late June planting is optimal for soybean in Kwara State. It recommends this planting window for extension recommendation and farmer advisory services.

Keywords: planting date, soybean yield, Kwara State, rainfall distribution, grain legume.