Effect of humic acid and foliar potassium applications on growth, yield and yield components of melon

A field study was conducted at the research field of research center Duhok province/Iraq at the summer growing season in 2019 to investigate the effect of humic acid and potassium fertilization and their interactions on the growth and yield of melon crop. The trial encompassed foliar spraying of potassium fertilizers at four levels (0, 0.3, 0.6, and 0.9 mg/L), and soil application of humic acid at four levels (0, 500, 1000, and 2000 mg/L). The experiment consisted of 16 treatments with three replicates in a completely randomized block design. The vegetative growth and flowering traits, some leaf mineral contents as well as some yield and quality characters and fruit mineral content were studied. The vegetative growth characters were not significantly influenced by humic acid and foliar application of potassium and their interactions at different doses in comparison with control. The effect of different doses of humic acid and potassium fertilization did not significantly increased most nutrient leaf content (N, Ca, and K) except (P) which was enhanced by application of both fertilizers. The yield quantitative characters of melon [number of fruits/ plant, total yield and fruit moisture content (%)] were not significantly different from control. The humic acid and foliar application of potassium fertilizer have a significant impact on the fruit content of phosphorus (P) and calcium (Ca) but did not remarkably enhanced nitrogen (N) and potassium (K) in fruits of melon. Both humic acid and potassium applications with different doses have resulted in a significant enhancement in carbohydrate content (%) in fruits and total soluble solids (TSS %), but did not cause any increment in the vitamin C compared to control. Keywords: Humic acid, Melon, Potassium, Quality, Yield