Effect of babassu mesocarp hydrogel on the initial development of watermelon seedlings

Abstract

This study evaluated the effects of babassu mesocarp hydrogel doses and irrigation frequency on the initial growth and water use efficiency (WUE) of Citrullus lanatus (‘Crimson Sweet’) seedlings in a completely randomized 2 × 5 factorial design, combining two irrigation intervals (24 and 48 h) and five doses of swollen hydrogel (0, 10, 20, 30, and 40 g per container, corresponding to 0, 40, 80, 120, and 160 mg of dry hydrogel). Under the 48-h irrigation regime, WUE increased from 0.000077 g mL⁻¹ in the control to 0.000198 g mL⁻¹ at the highest hydrogel dose, corresponding to a 157.1% increase. Under daily irrigation (24 h), WUE increased linearly with hydrogel dose, although the magnitude of this response was lower than under the 48-h irrigation interval. At the 48-h irrigation interval, increasing hydrogel doses linearly increased root length, stem diameter, fresh mass, total dry mass, and water use efficiency. Under daily irrigation, biomass accumulation showed no consistent dose-dependent response, and no significant linear or quadratic dose-response pattern was detected for most growth variables. At the 48-h irrigation interval, the highest hydrogel dose resulted in the highest numerical total dry mass and water use efficiency among the treatments within this irrigation regime, whereas increasing hydrogel doses under daily irrigation did not result in a consistent dose-dependent improvement in early shoot development.