Eficiência da adubação de cobertura com ureia revestida por polímeros na cultura do milho

Abstract

One of the most important aspects maize cultivation is the management of fertilization, in order to achieve maximum efficiency in the use of nutrients offered with fertilizers. Nitrogen (N) is the most required nutrient by maize. The source and the form of application of N can influence its use by the culture, since N is subject to important routes of loss, such as leaching, denitrification and, above all, volatilization. The fertilizer industry has invested in new manufacturing technologies, such as polymer-coated urea, which reduce the potential for loss and increase the efficiency of nutrient use by plants. The objective of this work was to compare conventional N fertilizers (common urea and ammonium sulphate) with an innovative source of N, provided with protective technology to minimize losses of the element, regarding the supply of N in topdressing fertilization to maize crop and the effects on plant biometry and soil fertility attributes. Conventional cultivation of maize, AG 8061 PRO 2 hybrid, took place in a dystrophic Oxisol, considering a high response to N and expected productivity of 8 to 10 t ha-1. The experiment was carried out under field conditions, in a completely randomized design, with 5 replicates and 4 treatments with N in the topdressing fertilization: T0 - control; T1 - ammonium sulfate; T2 - polymer-coated urea; T3 - common urea. At 150 days after planting, biometric evaluations of plant height, stem diameter, number of leaves above the ear, dry weight, productivity, weight per ear, and mass of a thousand grains were performed. Macro and micronutrients contents were determined on the diagnostic leaf for evaluation of the nutritional status of maize. At the end of the experiment, chemical analysis for soil fertility purposes, including N, was performed. The results were subjected to analysis of variance and, when significant by the F test (p<0.05), were evaluated by the Tukey test (p<0.05). The use of different sources of N did not influence the biometric and productivity parameters of the maize crop and the leaf contents of K, S and micronutrients. Leaf contents of N, Ca and, Mg were higher in maize plants fertilized with ammonium sulfate. Plants that received common urea showed higher P leaf levels. Leaf levels of P, K, S, Cu and Zn were insufficient, regardless of treatment. The N source did not cause changes in soil attributes, except for the Ca content and the cation exchange capacity, which were higher in the plots fertilized with common urea. Contrary to expectations, the N source did not cause changes in soil pH and residual N. Polymer-coated urea did not promote improvements in the biometric and productivity parameters of the maize crop and in the soil attributes, exhibiting performance similar to the conventional N fertilizers.