Zinc-Coated Urea with Gelatin-Enhanced Zinc Biofortification, Apparent Nitrogen Recovery, and Ryegrass Production

In alkaline soils, optimizing fertilizer use efficiency stands as a critical concern. Slow-release fertilizers enriched with essential micronutrients, particularly zinc (Zn), present a promising solution. The addition of bio-binders like gelatin can further improve their performance. This study assesses the impact of these coatings on ryegrass, with a specific emphasis on examining the influence of Zn and gelatin, a bio-binder, in enhancing nutrient absorption and crop yield. Slow-release fertilizers were prepared by coating urea with zinc oxide (ZnO) and gelatin using a fluidized bed coater, resulting in four formulations: G2, G2.5, ZnOG2, and ZnOG2.5. Various characterizations and agronomical tests were conducted to assess their performance. Physical and chemical analyses confirmed the uniform and strong coating, chemical composition, crystalline structure, and mechanical durability of the coated fertilizers. Soil analysis revealed remarkable results: soil mineral nitrogen levels reached 24.33 ± 0.97 kg/ha and soil-available zinc measured 5.1 ± 0.24 kg/ha. Additionally, ZnOG2.5 treatment improved soil health, enhancing microbial activity, with microbial biomass carbon at 210.5 ± 9.55 mg/kg and microbial biomass nitrogen at 69.2 ± 4.8 mg/kg. Plant responses were exceptional, with nitrogen (137.1 ± 10.52 kg/ha) and zinc (18.01 ± 0.86 kg/ha) uptake indicating potential of our slow-release fertilizer to boost plant nutrition. Significant improvements were seen in dry matter yield (7271.9 ± 330.06 kg/ha for shoots) and apparent nitrogen recovery (40.1 ± 4% for shoots), underscoring the practical benefits of our approach for nutrient utilization efficiency. Therefore, the utilization of ZnOG2 emerges as a viable option to enhance nitrogen uptake in the context of sustainable and environmentally friendly agricultural practices.