A Controlled-Release AgNPs and Rhizobium-Based Nanobio-Fertiliser Improves Tomato Growth and Minimises Nitrogen Consumption

Abstract

Biodegradable and soil-environment-safe controlled-release fertilizers (CRFs) represent a core, cutting-edge feasible pathway to enhance agricultural sustainability and reduce the production sector’s dependence on petroleum-based synthetic materials. This study focused on the research and development of controlled-release rhizobium (CRR) biofertilizer. We synthesized silver nanoparticles (AgNPs) using an environmentally friendly aqueous extract from neem (Azadirachta indica) leaves, and combined these particles with a starch-based polysaccharide nanocomposite to prepare a fertilizer efficacy carrier. The core research objective of this work is to improve nitrogen use efficiency (NUE) to support the sustainable production of tomato (Solanum lycopersicum L.). We conducted field trials that included 5 CRR formulations, each matched with three application rate gradients: 100%, 50%, and 25% of the recommended rhizobium dose. Conventional fertilization was set as the control group, and we measured four core indicators: plant growth, yield attributes, fruit quality, and NUE. Trial results show that the NUE of CRR treatment groups ranged from 47% to 88%, while the conventional fertilization control group only recorded an NUE of 33%. Even the agronomic performance of the 25% dose CRR treatment outperformed that of conventional fertilization. These findings confirm that CRR can reduce chemical fertilizer inputs and lower environmental impacts, and that this type of polysaccharide-based nano-biofertilizer is well-suited for nutrient management in tomato cultivation.