Submitted to: American Society for Horticultural Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/29/2005
Publication Date: 7/15/2005
Citation: Lester, G.E., Jifon, J.L., Rogers, G. 2005. Supplemental foliar potassium application to muskmelon (Cucumis melo L.) during fruit growth improves quality and content of human wellness components. Journal of the American Society for Horticultural Science. 130(4):649-653. Interpretive Summary: This glasshouse study demonstrated that supplementing soil potassium fertilization with a foliar applied glycine amino acid complexed potassium, during fruit development and maturation, increases orange-flesh muskmelon fruit quality (increasing sugar content, soluble solids, firmness and color) and human wellness compounds (increasing ascorbic acid, beta-carotene, and potassium ions). These quality improvements were obtained by implementing a relatively simple and inexpensive management tool that growers can easily adopt, particularly for melons grown in greenhouses or on K-deficient sandy soils.
Technical Abstract: Muskmelon fruit sugar content is directly related to potassium (K)-mediated phloem loading and unloading of sucrose into the fruit. However, during fruit growth and maturation, soil fertilization is often inadequate (due to poor root uptake) to satisfy the demand for K in fruit growth as well as the other numerous K-dependent functions within the plant. Potassium uptake also competes with the uptake of Ca and Mg, two essential minerals needed for melon fruit membrane structure, function and postharvest shelf-life. Supplemental foliar-applied K could alleviate this problem especially during the critical fruit growth/maturation period. During the spring of 2003 and 2004, we conducted greenhouse experiments to determine the effects of timing of supplemental foliar K applications on fruit quality and health attributes of orange-flesh muskmelon [Cucumis melo L.(Retiulatus Goup) ‘Cruiser’]. Plants were grown in a greenhouse and fertilized with a regular soil-applied N-P-K fertilizer throughout the study. Entire plants, including the fruit were sprayed with a solution of a novel glycine amino acid-complexed potassium (Potassium Metalosate, 24% K), diluted to 4.0 mL•L-1, 3 to 5 days after anthesis (fruit set) and up to 3 to 5 days prior to abscission (full-slip). Three sets of plants were sprayed either: weekly, biweekly or not sprayed (control). Fruit from plants receiving supplemental foliar K matured on average two days earlier, and had significantly higher fruit K concentrations, soluble solids, total sugars, ascorbic acid (vitamin C), beta-carotene, and were firmer than fruit from control plants. In general, there were no differences in fruit quality aspects between biweekly or weekly treatments. The data demonstrate that fruit quality and marketability as well as some of the developmentally-induced K deficiency effects can be alleviated through foliar nutrition.