YIELD, MINERAL CONTENT AND ANTIOXIDANT ACTIVITY OF COWPEA BEANS BIOFORTIFIED WITH COMBINATIONS OF FERROUS AND ZINC SULFATES

Abstract

Deficiencies in micronutrients can reduce the yield of legumes, the second more important food for human consumption. To counteract iron (Fe) and zinc (Zn) deficiencies in staple crops, agronomic fertilization techniques are applied, which are important in traditional crops. The objective of this study was to evaluate the effect of the application of ferrous sulfate (FeSO₄-7H₂O) in combination with zinc sulfate (ZnSO₄-7H₂O) on yield, mineral content and antioxidant activity of biofortified cowpea beans (Vigna unguiculata). The hypothesis was that at least one combination of these compounds would improve bean yield and nutritional quality. The experimental design was completely randomized in a factorial arrangement with three replications. The first factor was FeSO₄-7H₂O application rate (Fe1-Fe4: 0, 25, 50, 100 μM L^-1), and the second factor was ZnSO₄-7H₂O rate (Zn1-4: 0, 25, 50, 100 μM L^-1). Sixteen treatments were the result, which corresponded to the combination of levels of the factors. The application of the treatments increased yield (p≤0.05) from 15.6 to 51.0%; also, Fe content from 21.1 to 36.8%, Zn content from 1.1 to 12.7%. Total phenolic content from 1.8 to 30.5% and antioxidant activity from 1.5 to 35.2%. The study showed that biofortification with ferrous sulfate in combination with zinc sulfate can be an alternative to increase yield, mineral content and antioxidant activity in cowpea bean.