Formas de adição de micronutrientes a um formulado NPK e seu efeito sobre o desenvolvimento do milho

Abstract

Micronutrients are required in small amounts by plants and are essential for their development; however, micronutrient content in soil often is not sufficient to ensure high productivity, which creates the need for its application through fertilizers. This study compared availability of boron, copper, manganese and zinc to the soil, their absorption, accumulation and effect in developing maize plants, supplied from a physical mixture of NPK granules and micronutrients or from a granulated mixture NPK coated with these micronutrients. Two experiments were conducted in a greenhouse, one with Oxisol soil and AG1051corn hybrid for the first experiment and the other with an Ustox typical soil and DKB 390 VTPRO corn hybrid used in the second experiment. The formulation used was 04-30-10 (N-P2O5-K2O) with 0.1% B, 0.2% Cu, 0.2% Mn and 0.3% Zn. In both experiments, a randomized block design with four replicates were used and the formula NPK doses used were 0, 150, 300, 600, 1200 or 2400 kg ha-1. To ensure that all treatments received the same NPK amount, complementary doses of 04-30-10 without micronutrients were applied so that all treatments received the equivalent of 2400 kg ha-1 of formulated and therefore the same doses of nitrogen, phosphorus and potassium, varying only the micronutrients doses. Coating NPK granules with micronutrient was better than the physical mixture of granulated micronutrient with NPK when comparing zinc concentration in the soil; similar increments in boron contents and greater availability of copper were observed. The dry matter production of maize shoots was greatest with micronutrient coated NPK fertilizer. Also the accumulation of boron, manganese, copper and zinc in shoots of maize plants was greater when the granules of NPK fertilizer were coated.