Silica and polymer coated controlled release nitrogen-phosphorus fertilizer for improving nutrient and water use efficiency in semi-arid India

Improving the utilization of water and fertilizer nutrients, particularly nitrogen (N) and phosphorus (P) in semi-arid degraded land is utmost important. A double-coated, and water-retentive controlled release silica coated NP fertilizer (CSNPF) adaptable to varying temperature and soil moisture regimes was developed. The prepared NP nutrient core was coated with poly-vinayl alcohol (PVA) and silicon (Si). The SEM revealed that CSNPF was spherical heterogeneous crystals. The FTIR analysis indicated a stable nature of CSNPF. It contained ~ 17.30% N and 44.70% P2O5. During incubation, the CSNPF released ~61 and 64% P at 25 and 35°C, 65 and 70% P at 25 and 35°C, and 68 and 72% P at 25 and 35°C under 1.0, 0.67, and 0.33 bar soil moisture suction, respectively, confirming release of adequate nutrients under high temperature and dry soil also. The N and P release rates of CSNPF were ~25-38% slower than commercial di-ammonium phosphate (DAP) under varying temperature and moisture. During field experiment, application of 75% of N and P through CSNPF resulted in higher biomass yield of sorghum (62%) and oat (42%) than N and P application through commercial sources. Nutrient application through CSNPF improved P use efficiency (up to 20-22%) and water use efficiency of crops (by 20-28%). The CSNPF significantly improved soil structure, water holding capacity, microbial population, and their activity due to the presence of Si in it. Hence, the novel CSNPF could be utilized as an alternative to commercial P-fertilizers for enhancing nutrient and water use efficiency in semi-arid regions.