Field application of chelated calcium: postharvest effects on cantaloupe and honeydew fruit quality

Commercially grown honeydew fruit (Cucumis melo Inodorus group) and netted cantaloupe fruit (C. melo Reticulatus group) in low-humidity regions of the U.S. are typically field packed, eliminating the possibility for postharvest chelated-calcium dip treatments to extend fruit shelf life. In this study, calcium treatments were applied to orange-flesh honeydew fruit commercially grown in 2001 and 2002 in Sacramento Valley, Calif. and orange-fleshed netted cantaloupe fruit commercially grown in 2002 in Imperial Valley, Calif., and Rio Grande Valley, Texas. Aminoacid-chelated calcium and mannitol-complexed calcium compounds were applied to field-grown plants at the rate of 2.3 L.ha(-1) (1 qt/acre) at 0, 1, 2, or 4 total applications during growth of honeydew and cantaloupe fruit. Applications were A) at female flowering, B) within 15 days (cantaloupe) or 20 days (honeydew) after flowering, C) within 30 days (cantaloupe) or 40 days (honeydew) after female flowering, and/or D) within 3 to 5 days before abscission. One application equaled (A) or (D), two applications equaled (A + B) or (C + D) and four applications equaled (A + B + C + D). Evaluations of fully abscised fruit were exterior and interior firmness, marketability, calcium concentrations, interior soluble solids concentration (sugars), and consumer preference (taste) following harvest and up to 3 weeks commercial/retail storage. Cantaloupe fruit at both locations did not appear to benefit from preharvest plant applications of calcium when compared to fruit from plants treated with water. Honeydew fruit, however, did and the benefit was observed both years. Honeydew fruit that received four preharvest plant applications of calcium, regardless of source, were generally superior in firmness, marketability, and had a higher calcium concentration than fruit from plants receiving water or one or two applications of calcium. Fruit sugars and taste were not affected by preharvest plant applications of calcium.