In several experiments, strong negative correlations were found between fruit and leaf N vs. fruit color and fruit N vs. firmness, but a positive correlation existed between fruit Ca vs. firmness in apples. Based on these relationships, several models were developed to predict postharvest quality using preharvest nutrient status. Quantity and timing of N application to produce optimum-quality fruit in `Delicious', `Fuji', and `Gala' apples have also been investigated. High levels of nitrogen adversely affected fruit quality and increased endogenous ethylene and respiration. In separate experiments, the effects of seven post-bloom CaCl2 applications on various postharvest pathogens were studied in four apple cultivars. Calcium applications did not increase fruit Ca sufficiently enough to reduce colonization or maintain firmness after 4 months of 0C storage, but did slightly reduce infection by these pathogens during the growing season.
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