The effects of plant population density on the growth and chemical composition of Lablab purpureus grown for fodder production in a semi-arid region

Lablab purpureus was grown in two 6-month field experiments in the Savannah region of Africa, with high rainfall and hot temperatures in the first 3 m onths, followed by low rainfall and cool temperatures until harvesting in J anuary. The experiments evaluated the effects of plant population density ( PPD), using rows at 70-, 110- and 150-cm intervals, on the yield and nutrit ive value of the crop. and the effect of an interim harvest on response to PPD. Lablab yield ha(-1) was increased to a greater extent by an increase i n PPD from 110 to 70cm interrow spacing than by an increase from 150 to 110 cm, and yield plant (1) decreased as PPD increased to a greater extent for double-harvested than for single-harvested plants. This suggested that high PPD in the early stages of growth is important to promote high crop yields in this environment, probably because it mitigates drought effects ill aut umn. The effects of PPD on herbage composition were small and suggested tha t plant maturity had not been greatly affected by density. It is concluded that the maintenance of plant cover in the early stages of growth is import ant for high yields in the Savannah region, which call be achieved by an in terrow spacing of no more than 70 cm and avoidance of an interim harvest.