Genotype by Planting Date Effects on Cowpea in Humid Fringes, Southeast Nigeria

Abstract

A two-year factorial arranged field experiment in randomized complete block design with three replications was carried out in 2014 and 2015 at Michael Okpara University of Agriculture Teaching and Research Farm, Umudike (latitude 05° 29'N; longitude 07° 33'E; altitude 122 m above sea level), Nigeria. The objectives were to assess growth and yield response of twenty newly released cowpea genotypes to different planting dates (July, August and September). Plant height, number of leaves/plant, number of branches/plant, shoot biomass, total dry matter, number of nodules/plant, weight of pod, number of seeds/pod, seed weight/pod and grain yield varied amongst the genotypes and across the different planting dates in both years. The association between grain yield and other variables analysed across both years was significant and positive except 100-seed weight and the phenological characters of the plant. Path coefficients analysis across two years indicated that seed weight/pod followed by number of branches/plant and number of seeds/pod had positive direct effect on grain yield of cowpea in contrast to characters that exhibited negative but direct effect on yield. The other traits had relatively negligible to low indirect effects that were positive through other component traits. The grain yield sequence of interaction between genotype and date of planting was in this order: IT06K-141 planted in July ＞ IT11K-61-82 planted in September ＞ IT99K-573-1-1 planted in August. IT06K-141 genotype was considered to be better endowed genetically while the mean across both years indicated August as appropriate planting date to ensure high and sustainable grain yield.