Zinc oxide nanoparticles coupled biochar-based slow-release fertilizer for enhanced nutrient efficiency and sustainable agriculture

The excessive use of synthetic fertilizers has resulted in environmental degradation and inefficient nutrient utilization. Biochar-based slow-release fertilizers offer a sustainable alternative by enhancing nutrient retention and reducing environmental impact, but their nutrient slow-release performance can still be improved for better efficiency. In this study, a new zinc oxide nanoparticles coupled biochar-based slow-release fertilizer using polyvinyl alcohol/starch encapsulation is developed. The resulting PVA/ST-Zn-BSRF exhibits slower nutrient release than traditional NPK fertilizer and PVA/ST-NPK without ZnO/biochar incorporation. After 7 hours, it releases 145.15 mg of nitrogen and 23.25 mg of phosphorus in water, compared to 181.47 mg and 53.23 mg for NPK, and 168.08 mg and 34.27 mg for PVA/ST-NPK, respectively. In soil, PVA/ST-Zn-BSRF releases 5.82 mg of nitrogen and 1.22 mg of phosphorus over 29 days. The slow-release mechanism of PVA/ST-Zn-BSRF for nitrogen and phosphorus is attributed to the combined effects of Zn-BC adsorption and the physical diffusion barrier provided by the PVA/ST membrane. Field trials reveal that PVA/ST-Zn-BSRF boosts wheat yield by up to 87.5 % and significantly improves soil organic matter, with levels 25 % higher than those achieved with NPK treatment at grain maturity. Economic analysis reveals that, despite a higher fertilization cost, PVA/ST-Zn-BSRF leads to higher wheat yields and additional profit of $615.89/ha, demonstrating its potential for improving both agricultural productivity and sustainability. • PVA/ST-Zn-BSRF releases nutrients more slowly than PVA/ST-NPK and NPK fertilizers. • Field trials show up to 87.5 % increased wheat yield with PVA/ST-Zn-BSRF. • PVA/ST-Zn-BSRF enhances soil organic matter, 25 % higher than NPK. • Economic analysis shows an additional profit of $615.89/ha with PVA/ST-Zn-BSRF.