Mitigating Soil Salinity Stress in Spinach (Spinacia oleracea): The Role of Zinc-Chitosan Nanoparticles as a Foliar Spray

Salinity stress negatively affects the growth and nutrients uptake of vegetables. Using zinc-chitosan nanoparticles (Zn-chitosan NPs) to reduce salt stress in spinach was studied. In a greenhouse experiment, spinach plants were irrigated with three levels of saline water (3, 5, 7 dS m-1) and Zn-chitosan nanoparticles (NPs) solution was foliar sprayed at concentrations of 0, 100, and 200 ppm of NPs. Nutrients content and uptake in spinach, soil chemical characteristics, and spinach physiological parameters were analyzed after harvest. The saline water increased the soil salinity (ECe), soluble ions concentration, soil sodium adsorption ratio (SARe), and soil exchangeable sodium percentage (ESP). Salinity reduced soil available nitrogen and slightly increased available phosphorus and potassium. Saline stress decreased the nutrients content and uptake, while increased sodium in spinach. Salinity stress caused decrease in the spinach’s physiological parameters. Foliar spray with 100 ppm Zn-chitosan NPs improved spinach growth, nutrients uptake, K/Na and Ca/Na ratios, membrane stability, protein, soluble carbohydrates, carotenoid, chlorophyll, and antioxidant enzyme activities while decreased sodium accumulation. Zn-chitosan nanoparticles may aid in salinity mitigation for vegetables production, enhancing agriculture's resilience and food security.