Salicylic Acid Reduces Salinity Stress in Barbados Cherry Irrigated with Oilfield Water in Semiarid Brazil

The Barbados cherry (<i>Malpighia emarginata</i> DC) is a fruit crop of significant economic, social, and nutritional importance, particularly in Northeast Brazil. Its sustainable cultivation in semiarid regions depends on irrigation due to the negative water balance during most months. Given water scarcity, strategies such as using lower-quality water, including brackish water, wastewater, and oilfield produced water (OPW), have been investigated. These water sources, combined with proper irrigation management and salicylic acid (SA), can mitigate abiotic stresses like salinity. This study evaluated Barbados cherry rootstock production under irrigation with synthetic OPW and SA concentrations at the Federal Rural University of the Semi-Arid Region, CaraúbasRN, Brazil. A randomized block design with a 5 × 4 × 2 factorial arrangement and four replications was used. Treatments included five OPW dilutions in supply water (SW): D1 (100% SW), D2 (75% SW + 25% OPW), D3 (50% SW + 50% OPW), D4 (25% SW + 75% OPW), and D5 (100% OPW), combined with four SA concentrations (0, 0.8, 1.6, and 2.4 mM) and two genotypes (<i>Junco</i> and <i>Crioula</i>). Results show that OPW, combined with SA, enables irrigation in semiarid regions, reducing improper OPW disposal and promoting water conservation. The average SA concentration of 1.3 mM alleviated saline stress effects up to 2.63 dS m^-1, enhancing biomass production and seedling quality. The OPW-D3 dilution (50% SW + 50% OPW) was most effective for seedling morphophysiology, with <i>Junco</i> showing the best quality and <i>Crioula</i> exhibiting greater saline stress tolerance. These findings highlight the potential of combining OPW and SA as a sustainable strategy for Barbados cherry seedling production under saline conditions.