Potassium ferrite nanoparticles on DAP to formulate slow release fertilizer with auxiliary nutrients

Low use efficiency of nitrogen (N) and phosphorus (P) is major challenge of modern agriculture. Coating of conventional fertilizers with nanomaterials is a promising technique for improved nutrient use efficiency. In current study, nanoparticles (NPs) of potassium ferrite (KFeO₂ NPs) were coated on di-ammonium phosphate (DAP) fertilizer with three rates (2, 5, 10%) of KFeO₂ NPs and were evaluated for release of N, P, K and Fe supplementation in clay loam and loam soil up to 60 days. The NPs were characterized for crystal assemblage, bond formation, morphology and configuration using the x-ray diffraction (XRD), scanning electron microscope (SEM) and Fourier transform-infra red spectroscopy (FT-IR). The results showed that size of NPs ranged between 7 and 18 nm. The controlled release of P in 10% KFeO₂ nano-coated DAP was observed throughout the incubation period. The P release kept on increasing from day-1 (14.5 µg g^-1) to day-60 (178.6 µg g^-1) in coated DAP (10%) in loam soil. The maximum release of 50.4 µg g^-1 NH₄⁺¹-N in coated DAP (10%) was observed after 30 days of incubation. The release of NO₃^-1-N was consistent up to 45 and 60 days in clay loam and loam soil, respectively. The average release of potassium and iron in 60 days was 19.7 µg g^-1 and 7.3 µg g^-1 higher in 10% coated DAP than traditional DAP in clay loam soil. It was concluded that KFeO₂ nano-coated DAP supplied P and mineral N for longer period of time in both soils, and some higher coating levels should be tested in future.