Evaluation of cowpea (Vigna unguiculata (L.) Walp) genotypes for nodulation performance and biological nitrogen fixation in the lowlands of Southern and Southwestern Ethiopia

Abstract

Cowpea has a great potential in biological nitrogen fixation (BNF) and plays a significant role in cropping systems. However, information is scanty on the BNF potential of cowpea in Ethiopia. The study was therefore conducted to compare and select superior genotypes of cowpea for nodulation performance, BNF potential and biomass accumulation. The experiment was conducted during the 2019 main cropping season in the lowlands of southern and southwestern Ethiopia. The trial consisted of five pipeline genotypes (G) (ILRI-9333, ILRI-9334, ILRI-12713, and ILRI-12688) and released variety, Temesgen. The trial was laid out in randomized complete block design with three replications at the two locations (L). Data on nodulation, BNF and biomass yield were collected and subjected to ANOVA using SAS version 9.3. Results showed that G, L and G*L significantly (p<0.05) affected nodulation, BNF and biomass yield of cowpea. But effective nodules per plant and percentage of N- derived from atmosphere (% Ndfa) were significantly (p≤0.001) affected by genotype. Higher nodules dry weight per plant (1.46 and 0.82 gm per plant) and dry biomass yield (8.5 and 8 t/ha) were obtained from genotype ILRI-9334 followed by ILRI-12688, respectively. The highest number of nodules per plant (70.9), total nitrogen (116.8 kg ha^-1) and N-fixed (105.5 kg ha^-1) were obtained from ILRI-11114 followed by ILRI-12688. The highest Ndfa (90.4 %) was recorded for genotype ILRI-11114 followed by ILRI-12688. Generally, genotype ILRI-12688 showed better performance in biomass yield and biological nitrogen fixation potentials in the study areas. Based on this finding genotype ILRI-12688 is tentatively recommended for study areas and other places with similar agro-ecologies.