Zein coated porous carboxymethyl starch fertilizer for iron promoting and phosphate sustainable release

Abstract The low utilization efficiency of phosphorus (P) leads to limited uptake in plant and decrease of productivity in the world’s arable soil, which is due to the low solubility and immobilized interaction through Fe- and Al-based oxides. Therefore, there are only several reports for fertilizers containing both phosphorus and iron. To enhance the utilization efficiency of P and simultaneously provide available Fe, porous carboxymethyl starch (PCS) was synthesized as an absorbent for P and coated by zein. Fe(III) ion, a microelement for chlorophyll synthesis, was introduced as a bridge between PCS and phosphate anions. Then a fertilizer PCS-Fe-P/zein was developed. The content of P was as high as 166 mg/g, far more than other related fertilizers. The adsorption kinetics and isotherm were determined, and a potential adsorption mechanism was proposed. Diffusion of P from the fertilizer was examined in red soil and silt loam. The cumulative release of P in water from PCS-Fe-P/zein was 18% in 30 days, exhibiting a sustainable release behavior. Soybean was used to evaluate the fertilizing effect of PCS-Fe-P/zein. The total P uptake and utilization efficiency were determined. It is indicated from the pot experiments that the utilization efficiency of P was about 68%, three times higher than NH4H2PO4. These results demonstrated the potential and sustainable application of PCS-Fe-P/zein in agriculture.