Nodulation, biomass and yield of erect type cowpea genotypes in Uganda

Abstract

Cowpea is a major legume in Uganda, ranked fourth after beans, groundnuts and soybean. It is grown mainly in eastern and northern Uganda for human consumption and animal feed. Not much research has been done on cowpea especially with respect to crop improvement. As such, farmers largely grow landraces that are low yielding and susceptible to major constraints. On-going research to address these limitations have identified improved varieties, for which additional agronomic information is required. A field study was conducted at Makerere University Agricultural Research Institute, Kabanyolo (MUARIK), Uganda, during 2015 second rains to determine the effect of nodulation and biomass on yield of 54 erect cowpea genotypes. The genotypes were planted randomly in plots and then in two replications. Parameters evaluated included: Nodulation (determined on a scale of 0-5 due to presence of nodules at root zone), biomass (total sum of mass of branches, leaves and roots) (g) and yield (seed weight) (kg/ha). There was more variability (CV = 60%) among yield values than among biomass values (CV = 26.3%) and root nodulation values (CV = 46.4%) relative to their respective means (2.65 for root nodulation and 253.16 for biomass). A strong correlation (r= 0.735) occurred between nodulation and yield (at 1% level of significance) with a positive linear relationship after regression analysis. There was a weak correlation (r= 0.042) between biomass and yield at 1% level of significance; absence of a linear relationship was confirmed after regression analysis. Higher mean root nodulation was observed for landraces from northern and eastern Uganda (NE) and IT genotypes from Nigeria while the crosses showed a higher biomass accumulation. Genotype NE 51 x SEC 3 had 464g as the highest mean biomass. Landraces from western and central Uganda (WC) had some of the highest mean yields in the data (WC 64 = 2674.18) and genotype WC 16 with 182.50 kg/ha had the lowest mean yield. Further studies are recommended in more seasons and location to validate these results.