Effect of Zinc Chelate and Sulfate on Mineral Content, Antioxidant Activity and Grain Yield of V igna unguiculata L.

The study evaluated the effect of applying different doses of zinc sulfate and zinc chelate on the mineral content, antioxidant activity, and yield of grains of cowpea bean (Vigna unguiculata L.). Doses of 7, 14, and 28 mM L-1 of zinc sulfate and chelate were assessed against a distilled water control. In the plants, the days to flowering as well as grain weight, number of pods, and number of grains per plant were recorded. Meanwhile, in the grains, antioxidant activity, phenols, phytic acid, and mineral content were determined. Results indicated that biofortification with 7 and 14 mM L-1 of sulfate and zinc chelate increases earliness in flowering, the number of grains per plant, and the grain yield in addition to improving the mineral content of the grains. The highest antioxidant activity was found with the zinc chelate treatments. Phenol content increased with the zinc chelate and sulfate doses, while the phytic acid content decreased with respect to the control. Biofortification of cowpea beans with zinc chelate and sulfate at 28 mM L-1 induced the highest accumulation of Zn in cowpea seeds. It is thus feasible to implement a biofortification program with zinc in cowpea beans to increase the zinc content, the mineral content, antioxidant activity, and phenol content in the grains, as well as to decrease the phytic acid content.