Abstract
Calcium (Ca) is a major plant nutrient that affects cell wall and plasma membrane formation and plays a key role in growth and biomass production in plants. It can be used to decrease fruit decay and increase firmness and storage duration. So far, little attention has been paid to investigate the effects of foliar application of Ca on papaya under controlled environment, especially with respect to variety 'Eksotika II'. Therefore, this study was conducted to look at the effect of different sources and concentrations of Ca on nutrient concentration and growth of papaya. Papaya seedlings were established in pots and irrigated with a standard nutrient solution in a net house. Four pre-harvest sprays were applied as foliar applications with three different sources of Ca (calcium chloride, calcium nitrate and calcium propionate) at four different Ca concentrations (0, 60, 120 and 180 mg L-1). Spraying started one month after transplanting of seedlings and was carried out every 2 weeks for two months. Results showed that leaf Ca concentrations were not affected significantly by the different sources of Ca. However, increased Ca concentration applied to the leaves enhanced concentration of phosphorous (P) and Ca, but with a decrease in potassium (K) and magnesium (Mg) concentrations in the tissues. In addition, there were significant differences between control and 180 mg L-1 Ca for stem height and diameter, while the highest measurements were related to the 180 mg L-1. Based on these results, different sources and concentrations affected mineral nutrient concentrations and root growth differently. So, the choice of Ca source and concentration will be investigated subsequently.