Nano-Urea Enriched with Indigenous Mixture of Organic Inputs Alleviates Salt Stress to Sustain Tomato Production

This study developed an innovative fertilization framework integrating nano-urea with diverse organic amendments to enhance nutrient efficiency, salinity tolerance, and productivity in tomato (Solanum lycopersicum L. cv. Pusa Sheetal). Conducted over two years (2021–23) in Noida, India, the research employed a randomized block design to compare various combinations of nano-urea foliar sprays (2% and 4% w/v) and organic amendments, including farmyard manure, vermicompost, organic cakes, under both normal and saline (EC 4 dS m−1) conditions. Results demonstrated that replacing conventional nitrogen doses with integrated nano-urea and organic treatments significantly improved soil health by increasing soil organic carbon (up to 37%), macronutrient availability (N, P, K) while reducing electrical conductivity (up to 24.4%) in saline soils. Morphologically, the synergy between nano-urea and organic matter mitigated salt stress, resulting in substantial increases in plant height (21–25%), branching (13–26%), leaf production (13–24%), fruit number (20–53%), fruit weight (23–30%), and overall yield (44–89%) compared to control and saline-only treatments. Biochemically, the integrated approach upregulated the plant’s antioxidant defense system, showing significant increases in ascorbate peroxidase (34–74%) and superoxide dismutase (35–68%) activity. Concomitantly, a reduction in reactive oxygen species (ROS), hydrogen peroxide, and malondialdehyde (MDA) levels indicated a mitigation of salinity-induced oxidative damage. In addition, fruit quality was enhanced through elevated levels of carotenoids, lycopene, and vitamin C. Overall, the findings reveal a synergistic nutrient-delivery framework where nano-enabled nitrogen, coupled with organic amendments, optimizes rhizosphere chemistry and reinforces the ascorbate-glutathione cycle. This integrated approach represents a scalable, cost-effective advancement in precision nutrient management for sustainable tomato production in stress-prone agroecosystems.