Morphophysiology and production components of mini-watermelon under water replenishment and nitrogen fertilization levels

Abstract

In the semi-arid region of Northeast Brazil, the combination of irregular rainfall and high evapotranspiration creates a consistent water deficit in plants for most months of the year. This factor prominently limits the vegetable production potential. Consequently, finding effective strategies to alleviate the adverse impacts of water deficit on plants becomes imperative to ensure successful cultivation under irrigated conditions. Within this framework, the objective of this study was to evaluate the influence of nitrogen fertilization on both the morphophysiology and production components of 'Sugar Baby' mini-watermelon plants. The experiment was carried out at the 'Rolando Rivas Castellón' experimental farm in São Domingos, PB, Brazil, within controlled greenhouse conditions. A randomized block design was employed using a 4 × 4 factorial arrangement consisting of four distinct water replenishment levels (50, 75, 100 [control], and 125% of the crop's actual evapotranspiration [ETr]) and four nitrogen application rates (50, 75, 100, and 125% of the recommended rate). Each treatment combination was replicated three times, leading to a total of 48 plants being studied. Gas exchange parameters, content of photosynthetic pigments, relative water content, and electrolyte leakage were assessed. Furthermore, growth metrics, biomass production, production components, and the postharvest quality of 'Sugar Baby' mini-watermelon fruits were also evaluated. Subjecting the plants to deficit irrigation with 50% ETr reduced gas exchange, synthesis of photosynthetic pigments, growth, and fruit quality of 'Sugar Baby' mini-watermelon, irrespective of the nitrogen rate. On the other hand, the irrigation amount of 125% ETr coupled with nitrogen fertilization at 100% of the recommended rate provided higher values of total chlorophyll content, number of leaves, dry mass of root, stem, shoot, and total plant, and the pH value of 'Sugar Baby' mini-watermelon.