Desempenho agronômico de milho adubado com diferentes doses e fontes de ureia

Abstract

Corn is the main cereal produced in Brazil, cultivated in about 17.6 million hectares, with an average productivity of 5.56 tons per hectare, considering the first and second “off-season” crops. Nitrogen (N) is the nutrient absorbed and exported in greater quantity by corn, increasing the cost of crop production, the most difficult to assess its availability in the soil and the most complex management. In this context, the objective of this study was to evaluate the effect of nitrogen doses of different types of urea on the vegetative performance, nutritional status and productivity of corn, in the presence and absence of straw on the soil surface. The study comprised two experiments, being experiment I (Exp l) conducted in plastic pots and experiment II (Exp II) under field conditions. Exp I was carried out in pots arranged in the open, filled with 25 kg of dystroferric Red Latosol soil, cerrado phase, while exp. II was carried out under field conditions, in a dystroferric Red Latosol, the experimental design of exp I was in randomized blocks, with 24 treatments and four replications, in a 4x3x2 factorial scheme, with treatments of five doses of N: 30, 60, 120 and 180 kg ha-1; and three types of urea: conventional; with NBPT (N-(n-butyl) thiophosphoric triamide) in the composition, and urea with Duromide in the presence and absence of straw on the soil surface. As for the ex. II, a randomized block design was also used, in a factorial scheme with three 3x5 replications, with 15 treatments and 36 plots consisting of three types of urea, traditional urea, NBPT-treated urea (SuperN) and Duromide-treated urea (SuperN PRO). The second factor was five doses of N, being: 0, 30, 60, 120 and 180 kg ha-1. In the first experiment, the stem diameter, plant height, number of grains per ear, nutritional status, shoot dry mass and grain yield were evaluated; for the second test, the variables analyzed were the weight of a thousand grains and their productivity. In the Exp l treatments did not differ for grain yield, only the cultivation in an environment with straw on the ground had an effect on the stem diameter of corn plants. For Exp ll, only N doses influenced grain yield and the results of the 1000-grain mass, so the highest dose (180 kg ha-1 of N) obtained the best results.