Submitted to: Acta Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 12, 2004
Publication Date: June 30, 2005
Citation: Lester, G.E. 2005. Whole plant applied potassium: Effect on cantaloupe fruit sugar content and related human wellness compounds. Acta Horticulturae. 682:487-492.
Interpretive Summary: This controlled environment greenhouse study demonstrated that whole plant (foliar/fruit) applied K can increase cantaloupe fruit quality, by increasing simple carbohydrate content, ascorbic acid and beta-carotene levels. These studies will be repeated in both greenhouse as well as in field trials. It is expected that these foliar/fruit K applied trials, will be as encouraging, in demonstrating the dramatic benefit to muskmelon fruits (both cantaloupe and perhaps honey dew melons) in improving K content and subsequently increasing soluble solids concentration, total sugars, ascorbic acid and beta-carotene contents. Thus, melon fruit quality and marketability are expected to benefit by following this relatively simple and inexpensive management tool.
Cantaloupe fruit sugar content is directly related to potassium (K)-mediated phloem loading and unloading of sucrose into the fruit. Improving K content in melons, during fruit growth and maturation through soil applied fertilization, is a problem, as root uptake of K is poor at this stage of growth and K competes with the uptake of Ca and Mg, two essential minerals needed for melon fruit membrane structure, function and postharvest shelf-life. Netted, orange-flesh muskmelon [Cucumis melo L. (Reticulatus Group) 'Cruiser'] fruits were grown in the greenhouse during the spring of 2003 and received regular N-P-K soil fertilization throughout the study. Three to 5 days after anthesis (fruit set) and up to 3 to 5 days prior to abscission (full-slip), amino acid complexed potassium (Potassium Metalosate 24% K) at 4.0 mL.L-1 (0.51 oz.gal-1) was sprayed on the leaves and fruit until run-off. Plants were sprayed either weekly, biweekly or not sprayed (control). Fruit from plants receiving weekly applications of foliar/fruit K matured two days earlier, and had significantly higher fruit K content, soluble solids concentration, total sugars, ascorbic acid (vitamin C), and beta-carotene content than fruit from plants not receiving foliar K applications.