Effects of Moisture Deficit on the Yield of Cowpea Genotypes in the Guinea Savannah of Northern Ghana

Abstract

Cowpea is multipurpose, leguminous, high protein crop in the tropics that provides food for humans and fodder for animals. The crop adds nitrogen and other nutrients to the soil through symbiotic relationship with rhizobia and direct decomposition of cowpea by-products. Despite its multiple benefits for humankind, the yield of cowpea is far below its potential and its production in the crop’s birthplace of Africa is especially affected by abiotic factors. Soil moisture deficit is one of the main abiotic factors that affect the yield of cowpea in the semi-arid tropics, including the Sahelian and Guinea Savannah regions in West Africa. Even though cowpea is a drought tolerant legume, different genotypes respond differently to drought, resulting in up to 100% or more yield increases in the case of resistant genotypes or 50% or more yield loss in case of susceptible types. Mitigating the effect of soil moisture deficit on cowpea production requires selection of genotypes that can withstand drought. With this in mind, the goal of this study was to identify drought tolerant cowpea germplasm for the Savannah region of Northern Ghana using cultivated genotypes from the United States Department of Agriculture (USDA) tested with and without irrigation at the Bontanga irrigation facility during the dry season in 2018. Fifty genotypes were used, which included 45 imported from USDA and five (5) local genotypes from the Savannah Agriculture Research Institute (SARI). The experiment had 2 × 50 factorial treatments (irrigation × genotypes) and consisted of randomized complete block design with three (3) replications per treatment. Two (2) watering regimes were introduced namely, drought stressed (no irrigation) and non-stressed/control (irrigated). Morpho-physiological, phenological and yield data were taken on the cowpeas evaluated with drought tolerance assessed based on grain yield data and derived indices. All parameters measured showed significant differences (p ≤ 0.05) except for the number of branches per plant. Genotypes PI339600, PI527263, PI527302, PI582793, PI582867 and SARI-6-2-6 produced high grain yields under both drought stress and non-stress conditions. These genotypes could be exploited for future breeding programs for developing drought tolerant cowpea varieties for the savannah ecology and other areas with similar environmental conditions.