Protein content variation in cowpea genotypes (Vigna unguiculata L. Walp.) grown in the Eastern Cape province of South Africa as affected by mineralised goat manure

Abstract

Nutrients availability of cultivated soils in the Eastern Cape region of South Africa is generally low, and recognizing that manure application has been one of the most effective methods to improve soil fertility and crop yield in tropical African countries, we assessed the effect of manure application on the leaf crude protein content of six cowpea genotypes (Vegetable cowpea, Ivory grey, Okhalweni, Fahari, Fahari dark, and 97 K-1069-8) a green house experiment. Fresh leaves were collected from each cowpea plant 21 days after planting and ground in liquid nitrogen for protein extraction and quantification. The results showed that Fahari had the highest concentration of crude protein (46.51 mg/ml) while vegetable cowpea (24.41 mg/ml) had the lowest without the influence of manure application. However, upon application of manure (goat), Fahari dark had the highest crude protein concentration (53.53 mg/ml) while vegetable cowpea had the lowest (29.08 mg/ml). Fahari, 97K-1069-8, Ivory grey, and Okhalweni contained 51.79, 49.03, 44.83, and 38.33 mg/ml crude protein concentrations, respectively. This study demonstrated that genotypes as well as manure application significantly influenced cowpea yields in terms of its leaf crude protein content.