Optimizing spinach production in arid regions by integrating soil and foliar applications of micronutrients with organic fertilizers under saline irrigation

Abstract

This study aimed to optimize integrated nutrient management (INM) strategies to enhance the growth, yield, and biochemical composition of spinach under varying irrigation water salinity levels. A field experiment comprising twelve treatments was conducted using combinations of irrigation salinity (0.5, 2.0, and 4.0 dS/m EC), recommended dose of fertilizers (RDF), organic amendments (farmyard manure and vermicompost), and micronutrient applications (soil and foliar). The untreated control (T1), irrigated with 4.0 dS/m EC water alone, recorded the lowest plant height, leaf number, leaf area, dry matter, and yield, confirming the adverse impact of high salinity. In contrast, integrated nutrient treatments significantly improved spinach performance. The most favorable results were observed in Treatment 12 (0.5 dS/m EC + RDF + 50% FYM + 50% VC + foliar ZnSO₄ @ 0.5% + soil FeSO₄ @ 0.5%), which recorded the highest plant height (29.13 cm), leaf number (15.8), leaf area (11.45 cm² at 45 DAS; 16.76 cm² at 60 DAS), dry matter (6.89%), total soluble solids (6.77%), and total yield (266.8 kg/ha). Treatment 4, with 4.0 dS/m EC water and full INM inputs, showed comparable performance (yield: 261.2 kg/ha; plant height: 28.59 cm), highlighting INM’s potential under salinity stress. Biochemical analysis revealed that Treatment 3 (4.0 dS/m EC + RDF + 100% FYM + FeSO₄ @ 0.5%) showed the highest chlorophyll a (0.754 mg/g), chlorophyll b (0.293 mg/g), carotenoids (0.515 mg/g), and ascorbic acid (29.97 mg/100g). Overall, optimized INM effectively mitigates salinity stress, enhances physiological and biochemical traits, and promotes sustainable spinach cultivation in saline-prone areas.