Influence of Calcium Foliar Fertilization on Plant Growth, Nutrient Concentrations, and Fruit Quality of Papaya

Calcium (Ca) is a major plant nutrient that affects cell wall and plasma membrane formation and plays a key role in plant growth, biomass production, and function. Ca can be used to decrease fruit decay and increase firmness and shelf life. Different sources and concentrations of foliar-applied Ca were examined for the effects on nutrient concentration and growth of 'Eksotika IT papaya (Carica papaya) plants. Papaya seedlings were established in pots and irrigated with a standard nutrient solution in a net house. Four preharvest sprays were applied as foliar applications with three different sources of Ca {calcium chloride [CaCl2], calcium nitrate [Ca(NO3)(2)], and calcium propionate [Ca(C2H5COO)(2)]} at four concentrations (0, 60, 120, and 180 mg.L-1). Plant Ca concentration was unaffected by the different Ca sources. However, increased Ca concentration applied to the leaves enhanced plant accumulation of phosphorous and Ca in the plant, but decreased potassium (K) and magnesium (Mg) concentrations in the tissues. Plants that received Ca at 180 mg.L-1 had greater height and diameter than control plants. In a field trial with mature trees, preharvest applications of Ca (0, 4000, and 5400 mg.L-1) in the form of CaCl2 showed that increasing concentrations improved fruit Ca concentration, texture, and flavor; and decreased weight loss, Mg content, and apparent disease incidence of the fruit.