Effect of method of weed control and insecticide (Lambda-cyhalothrin) rates on the productivity of cowpea (Vigna unguiculata (L) Walp) in a Southern Guinea Savanna of Nigeria

Field trials were conducted in two locations, at the Teaching and Research (T&R) Farm of the College of Agriculture, Kwara State University and Ga-Alanu Village, Malete, in the 2015 cropping season. The aim was to determine the effect of method of weed control and insecticide rates (Lambda-cyhalothrin) on the growth and yield of cowpea. The experiment consisted of 18 treatments, namely, 3 insecticide rates (0 ml/ha, 175ml or 8.75g.a.i./ha and 350ml or 17.5ga.i/ha) and 6 methods of weed control (pendimethalin at 1.5kg a.i/ha, pendimethalin at 2.0kg a.i/ha, pendimethalin at 1.5 kg a.i./ha plus one supplementary hoe weeding (SHW), metholachlor + diuron at 1.5 + 0.6 kg a.i/ha, hoe weeding at 3 and 6 weeks after sowing (WAS) and a weedy check. The treatments were laid out in randomized complete block (RCBD) design fitted into split plot arrangement and replicated 3 times. Parameters measured were weed density, weed dry matter, relative importance value of weed species, plant height, crop vigour, number of pods/plot and grain yield. Data collected was subjected to analysis of variance and means were separated using Least Significant Difference (LSD) at 5% level of probability. Results showed that insecticide rates at 175ml and 350 ml/ha and pendimethalin at 2.0kg a.i./ha or pendimethialin at 1.5kg a.i/ha plus one SHW promoted good growth, development and higher yield of cowpea.