Influence of Soil Type and Foliar Potassium Fertilization On Fruit Quality and Phytochemical Contents of Muskmelon

Consumer Preference Quality attributes (e.g. sweetness, aroma, texture) are strongly influenced by potassium (K)-mediated processes such as protein synthesis, stomatal opening, photosynthesis, and assimilate transport. However, during fruit growth and maturation, soil K supply alone is seldom adequate to satisfy K requirements. The effects of soil type (sandy versus clay soil) and supplemental foliar K applications on quality and phytochemical content of muskmelon (cv Cruiser) fruit were investigated. Starting at fruit set and continuing to fruit maturity, weekly foliar K applications were established using four K salts (KCl; KNO₃; potassium thiosulfate - KTS; and Potassium Metalosate, KM).  Even though pre-plant soil K concentrations were very high (especially on the clay soil), supplemental foliar K treatments resulted in generally higher tissue K concentrations.  Fruit from plots receiving supplemental foliar K generally had higher soluble solids, sugars, and phytochemicals (ascorbic acid and β-carotene) than control fruit.  The relative responses to foliar K were generally greater on the sandy soil than the clay soil.  There were no consistent trends among K sources except for KNO₃ which tended to result in poor fruit quality compared to control fruit especially on the sandy soil. The results demonstrate that mid- to late-season foliar K applications can improve melon fruit quality and suggest that the relative benefit of this quality improvement strategy depends on soil type.  The data also reveal differences among potential foliar K salts and call for a reassessment of K management strategies aimed at improving fruit quality.