Growth and Nutritional Response of Melon to Water Quality and Nitrogen Potassium Fertigation Levels under Greenhouse Mediterranean Conditions

The Mediterranean area has been experiencing an extensive development of intensive horticulture, with a majority of that located in arid and semi-arid regions with limited water resources and poor water quality. One of the most important greenhouse vegetable crops is melon. This article studies the effects of different nitrogen–potassium (N–K) fertilizers applications and two types of irrigation water on yield and nutritional behavior of melon crop Cucumis melo L. (var. cantalupensis Naud. Alpes). The trial was conducted during two cycles under Mediterranean greenhouse conditions, on sandy mulching soil. The experimental design was bifactorial: NK fertigation and water quality, with three nutrition levels and two water qualities [MS with electrical conductivity (EC) = 0.6 dS m−1 and HS with EC = 2.3 dS m−1]. During the first cycle, the fertigation levels were F1 (50% NK), F2 (100% NK), and F3 (125% NK). In the second cycle, the fertigation levels were F2, F4 (125% N and 150% K) and F5 (180% N and 220% K). Treatment F2 was the recommended total doses (220 kg N ha−1 and 355 kg K ha−1). The increase in the NK concentration of the nutritive solution produced a rise in commercial production. The salinity of irrigation water did not affect marketable yield but had an effect on the fruit size, which was compensated for by an increase in the amount of fruit produced. Dry-matter production, N, and K uptake by plant (g m−2) were evaluated in the first and second trials. Salinity and NK nutrition levels significantly affected (P < 0.05) dry matter and N and K uptake by melon plant. Nitrogen and K uptake present interesting correlations with production and with each other, as established by mean regression analysis.