ABSTRACT
Improving phosphorus (P) use efficiency is a challenge to promote a circular economy and greening the phosphorus cycle towards planetary sustainability. The disruptive innovation for phosphate fertilizers may help to reduce some unwelcome reactions that occur to P in soils. Monoammonium phosphate (MAP) coating with biodegradable organic polymers and the addition of magnesium (Mg) - a nutrient with a synergistic effect on the uptake of P, zinc (Zn), and boron (B) - emerge as a smart strategy to applying these micronutrients uniformly in soils. The objectives of this study were: to characterize the coated-MAP with biodegradable organic polymers, quantify the diffusion and availability of P in the soil, and evaluate the corn crop nutrition and yield during two crop seasons. The treatments were: MAP, MAP coated with biodegradable organic polymer (BOP), MAP + BOP + 1.3% of Zn + 0.33% of B, and MAP + BOP + 1.76% of Mg. The laboratory tests showed that the diffusion of MAP-based fertilizers was: MOMg (7.86 mm) = MO (8.82 mm) = MAP (8.84 mm) = MOM (8.51 mm) after 432 h. Coatings did not cause delays in the P-release in water at 25 °C since more than 95% of P was released within 24 h. In the field trials, the application of Mg, Zn, and B in the MAP coating did not increase nutrient leaf concentration. In the summer crop season, grain yield increased up to the P-rates of 85 kg of P2O5 ha-1, reaching the value of 6731 kg ha-1. Physical and chemical characteristics of MAP-fertilizers tend to improve with the coatings. The addition of biodegradable organic polymers, Mg, B, and Zn, as MAP-coatings did not enhance P diffusion, release, and availability in the soil and the crop nutrition. Coated-MAP improved corn yield only in the 2nd crop season.
