Bioactivator, phosphorus and potassium fertilization and their effects on soil, physiology, production and quality of melon

The objective of this study was to evaluate the effect of the combination between doses of phosphate and potassium fertilizers and the use of soil and plant bioactivators on the physiology, production and quality of melon. The design was randomized block design, with four replicates. Five doses of phosphorus and five of potassium were evaluated, plus an additional treatment (no chemical fertilizer), totaling 10 P:K combinations, which were tested in the presence and absence of the bioactivator applied to the soil at the foundation, and cover applied to plants at 21, 27, and 35 days after transplanting. Leaf contents of N, P, and K, soil chemical fertility, gas exchanges, chlorophyll indexes, chlorophyll fluorescence, crop yield, and postharvest quality of melon plants were evaluated. The doses of phosphate and potassium fertilizer affected the residual concentration of phosphorus and potassium in the soil, plant nutrition, gas exchanges, and chlorophyll fluorescence, but did not affect the production and quality of melon. The bioactivator affected the internal concentration of CO2, stomatal conductance and improved the vitamin C content of melon, but had no effect on nutrition, physiology, production, and residual concentration of phosphorus and potassium in the soil at the end of the production cycle. Here, we found that upon previous application of 20 ton ha−1 of bovine manure to soil foundation, the combined P:K fertilization, as well as the use of bioactivator did not increase overall melon production and quality and, thus, their use is not recommended for Gladial melon.