MAP com polímero orgânico biodegradável e a adição de micronutrientes ou magnésio na nutrição do milho

Abstract

Phosphate fertilizers are widely used in world agriculture and phosphate rocks are considered a finite resource and may be scarce. Phosphorus (P) has a complex dy namic relationship in acid soils, being easily adsorbed and large amounts of nutrient are lost without being able to be used by plants. Organic matter has a direct and indirect relationship with P and may decrease its adsorption in soils. Due to this, the coating of monoammonium phosphate (MAP) with polymers, magnesium or micronutrients appears as an option to improve the agronomic efficiency of phosphate fert ilization. In this context, the objective of this study was to evaluate the organic polymers coating of MAP on corn cultivated in two distinct seasons, in the summer and in the second crop. The treatments used were MAP, MAP coated with biodegradable organic polymer (BOP), MAP coated with BOP + 1.23% Zn + 0.33% B and MAP coated with BOP + 1.76% Mg. Fertilizer characterization was evaluated for polymer biodegradability, diffusion, mobility and P availability. Polymer characterization was performed by MEV and IF-TR. In experiments conducted under field conditions for two harvests, increasing doses (0, 50, 100 and 150 kg P2O5 ha-1) of the treatments in seeding fertilization were applied and the leaf and nutrient grain contents, nutrient accumulation in grain, grain yield, and agronomic efficiency of fertilizers, were evaluated. For the characterization of the polymer, a biodegradability of 17.78% was verified in 44 days. Regarding P diffusion and availability, diffusion increased as a function of time up to 4 hours after fertilizer application, with a subsequent reduction followed by diffusion stability. As for availability, P was more available in areas adjacent to the site that received the fertilizer granules and there was greater P movement in depth in the sandy soil, when compared to the medium textured soil. It was observed that there was no increase in d iffusion, mobility and availability of P, as well as productivity, due to the coating using organic polymer, with addition of micronutrients or Mg.