Submitted to: HortScience
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/10/2006
Publication Date: 6/10/2006
Citation: Lester, G.E., Jifon, J.L., Makus, D.J. 2006. Supplemental foliar potassium application with or without a surfactant can enhance netted muskmelon quality. HortScience. 41(3):741-744. Interpretive Summary: Supplementing soil K with foliar K applications during muskmelon fruit development and maturation improved fresh fruit quality by significantly increasing firmness (26%), sugar content (20%), ascorbic acid (18%), '-carotene (17%), and K (14%) compared to non-treated fruit. Differences between the two K sources (an organic form, KM and an inorganic form, KCl) were minimal and use of a surfactant tended to have a positive effect on the response to supplemental foliar K applications. These quality improvements were obtained by implementing a simple management tool foliar applied K using generally available K compounds plus a surfactant (to plants with adequate root N-P-K) that growers can adopt all over the world.
Technical Abstract: Netted muskmelon [Cucumis melo L. (Reticulatus Group)] fruit quality (ascorbic acid, '-carotene, total free sugars, and soluble solids concentration (SSC)) is directly related to plant potassium (K) concentration during fruit growth and maturation. During reproductive development, soil K fertilization alone is often inadequate due to poor root uptake and competitive uptake inhibition from calcium and magnesium. Foliar applications of glycine-complexed K during muskmelon fruit development have been shown to improve fruit quality, however, the influence of organic-complexed K vs. an inorganic salt form has not been determined. This glasshouse study investigated the effects of two K sources [a glycine-complexed K, Potassium Metalosate (KM), containing 800 mg K•L-1] with or without a surfactant on melon quality. Orange-flesh muskmelon ‘Cruiser’ was grown in a glasshouse and fertilized throughout the study with soil-applied N-P-K fertilizer. Starting at 3 to 5 d after fruit set, and up to 3 to 5 d prior to fruit maturity at full slip, entire plants were sprayed weekly, including the fruit, with KM or KCl, with or without a surfactant. Fruit from plants receiving supplemental foliar K had significantly higher K concentrations in the edible middle mesocarp fruit tissue compared to control untreated fruit. Fruit from treated plants were also firmer, both externally and internally, than those from non-treated control plants. Increased fruit tissue firmness was accompanied by higher tissue pressure potentials of K treated plants vs. control. In general, K treated fruit had significantly higher soluble solids concentrations (SSC), total sugars, total ascorbic acid, and '-carotene than control fruit. Autumn-grown fruit generally had higher SSC, total sugars, total ascorbic acid and '-carotene concentrations than spring-grown fruits regardless of K treatment. The effects of surfactant were not consistent, but in general, addition of a surfactant tended to increase SSC and '-carotene.