Impact of Agronomic Biofortification with Zinc on the Nutrient Content, Bioactive Compounds, and Antioxidant Capacity of Cowpea Bean (Vigna unguiculata L. Walpers)

Zinc intake deficiency is a public health problem and increasing the nutrient’s content in the edible parts of plants can help mitigate it. The objective of this work was to determine the effect of the edaphic and foliar application of zinc sulphate on the nutrient content, bioactive compounds, and antioxidant capacity of cowpea beans (Vigna unguiculata L. Walpers). A sample of 100 grains was taken, and the length, width, thickness, weight, ash content, fat, humidity, fibers, carbohydrates, protein, energy, macro- and micro- nutrients, total phenols, flavonoids, anthocyanins, and antioxidant capacity were determined. The 0.250 g edaphic-12.5 mM foliar dose produced grains of a greater weight and size. All of the edaphic and foliar doses increased the grain zinc content, and the highest value was found with the 0.125 g edaphic-50.0 mM foliar dose. The total phenols increased with 12.5 g of edaphic zinc, while phenols, flavonoids, and the antioxidant capacity increased with 50.0 mM foliar zinc. The edaphic and foliar application of zinc sulphate increased the grain weight and size, zinc content, total phenols, and antioxidant capacity. Therefore, edaphic and foliar zinc biofortification enriches this nutrient in cowpea grains, and could reduce micronutrient malnutrition in the urban and rural communities of Mexico.