Optimizing Green Bean Yield: Controlled Nitrogen Release with Nano-Urea-Modified Apatite

Abstract

Controlled-release fertilizers (CRFs) have drawn significant attention because of their ability to improve plant nutrient uptake efficiency and mitigate environmental pollution. Current commercial CRFs need improvement to reduce synthesizing costs and to apply biodegradable materials and/or biorefinery wastes. In this study, CRFs were synthesized by treating nano-apatite with urea at different apatite:urea ratios (1:1 and 1:4). The biodegradable polymers, alginate, and lignin extracted from agricultural residue and paper manufacturing waste were used as single (alginate) and double (alginate and lignin) coating layers to form CRFs. In lab experiments, the N release behavior was studied in both water and soil. A cultivation experiment was carried out to study the efficiency of CRFs in the yield of green bean plants. The CRFs were applied with 3 N levels (75, 50, and 25% of the recommended dose). Both types of CRFs significantly increased the N release period to 24 days compared to 5 days for commercial urea. The total yield increased by 88 and 98% by applying double- and single-coated CRFs, respectively, at 75% N of the recommended dose compared with the full dose of conventional urea. In conclusion, applying CRFs at an N level of 25% of the recommended amount obtained the same yield as the full dose of conventional urea. KEYWORDS biodegradable coating, hydroxyapatite, lignin, nano-fertilizer, nitrogen efficiency, snap beans