Fine-tuning nutrient electrical conductivity in substrate hydroponics to boost growth and early fruit set of melon in a smart greenhouse

Hydroponic melon (Cucumis melo L.) production is constrained by the high cost of standard standard AB Mix nutrients. This study evaluated an economical alternative (½ AB Mix + ½ Gandasil) at varied Electrical Conductivity (EC) levels (3, 4, 5 mS/cm) against a standard control (100% AB Mix, EC 3) within a Smart Green House (SGH). The experiment revealed a significant paradox while high-concentration treatments (C1EC5 and C0EC3) acted as potent stimulants, significantly accelerating early vegetative growth and initial fruit set, this advantage was completely nullified by the final harvest. Analysis of variance (ANOVA) confirmed no significant difference (ns) across any critical yield parameters, including fruit weight, diameter, and sweetness (°Brix). The data demonstrates that a non-nutritional, overriding limiting factor suppressed the crop's potential. Supra-optimal thermal stress, with ambient SGH temperatures averaging 32°C, impaired photosynthetic efficiency and assimilate translocation. We conclude that in this system, meticulous environmental temperature control is an indispensable prerequisite that must take precedence over optimizing nutrient concentration to achieve viable yields.