Fruit production and quality of mini-watermelon with different number of stems, in troughs cultivation system and substrate reuse

Abstract

Substrate-filled pots are growing systems commonly used for vegetable farming. However, few are the studies available relating them to mini-watermelon cultivation. Our study presents a growing system using substrate-filled troughs and leachate recirculation as a low-cost and less environmentally harmful soilless cultivation system for mini-watermelons. For a growing system to be viable and provide high fruit yield and quality, several aspects must be studied, including substrate physical properties and reuse potential in successive crops, besides plant management-related aspects. Therefore, our goal was to evaluate the effects of a trough system and substrate reuse on changes in the properties of raw rice husk and on fruit yield and quality for mini-watermelons at different stem training. To this purpose, two trials were conducted using nutrient solution recirculation systems. In the first, we evaluated the effects of pot and trough systems. In the second, first- and second-use substrates were compared in the trough system. In both trials, one and two-stem training systems were analyzed. The results of the first trial show that the trough system had a greater positive impact on substrate water holding capacity (WHC), which increased from 7.9 to 15.6%, while the pots increased substrate WHC only to 11.2%. However, both systems neither affected fruit yield (8 kg/m² on average) nor fruit quality. The two-stem training promoted higher fruit yields (4.2 kg/plant) and contents of total soluble solids - TSS (11.4 °Brix) but did not affect average fruit weight. Moreover, the one-stem training provided higher fruit number (7.3 fruits/m²) and fruit yield (9.7 kg/m²). In the second trial, the reused substrate showed a higher WHC (12.4%) than the one used for the first time (9.9%). The reused substrate also provided better results in terms of fruit yield and quality (5.9 fruits/m², 5.3 kg/m², and 10.5o Brix). In the second trial, two-stem training also increased average fruit weight, and hence yields per plant. Nevertheless, the stem number did not affect fruit number per plant, fruit yield per square meter, and fruit quality.