Production and Post-Harvest Quality of Guava Under Saline Water Irrigation Strategies and Foliar Application of Ascorbic Acid

Saline water is a major constraint on irrigated fruit farming in the Brazilian semiarid region, negatively reducing both yield and fruit quality. Developing effective strategies to mitigate salt stress is therefore essential. This study evaluated the effects of foliar application of ascorbic acid (AsA) on guava production and post-harvest quality under different phase-specific saline water irrigation strategies. The experiment was arranged in a randomized block design with split-plots. The main plots consisted of six irrigation strategies, which consisted of continuous irrigation with moderately saline water (0.9 dS m^-1) and irrigation with saline water (3.3 dS m^-1) applied during specific growth stages (vegetative, flowering, fruiting, vegetative/flowering, and vegetative/fruiting). Subplots received a control and three AsA concentrations (0, 200, 400, and 600 mg L^-1). Irrigation with saline water (3.3 dS m^-1) did not reduce yield, as fruit number and weight were maintained relative to the control. The main effect of saline stress was on fruit chemical composition: flavonoid and anthocyanin contents increased under saline irrigation, while stress during the fruiting stage elevated non-reducing sugars and the maturation index. Foliar AsA application acted as a biostimulant, with 600 mg L^-1 improving production by increasing average fruit weight and enhancing nutritional quality through higher soluble solid, reducing sugar, and vitamin C contents. These results highlight the potential of combining phase-specific saline irrigation with AsA application to improve guava fruit quality in the Brazilian semiarid region.