CARACTERES MORFOLÓGICOS, ESTADO NUTRICIONAL E PRODUTIVIDADE DE MILHO CULTIVADO SOB DOSES E FONTES DE NITROGÊNIO

Abstract

Maize is the main cereal produced in Brazil and is grown on approximately 18.5 milion hectares, with a production of approximately 105 milion tons of grain, and an average of 5.69 tons per hectare, considering first and second crop “safrinha”. Low consumption and incorrect handling of nitrogen (N) are one of the factors responsible for low productivity of this crop. Given the above, the objective of this study was to evaluate the vegetative development, productivity, extraction and export of macronutrients, for the maize crop a function of nitrogen source and rates. The experiment was carried out under field conditions, in the experimental area of the Federal Institute Goiano – Campus Rio Verde, Brazil. The experimental design in randomized blocks, with 10 treatments and three replications, arranged in a 5x2 factorial scheme. The treatments comprised five rates of N (0, 40, 80, 120 e 160 kg ha-1) and two sources of N: ammonium nitrate (33% N) and urea (45% N). The plant height was evaluated, stem diameter, dry straw mass, ear length, ear diameter, cob length, cob diameter, number of rows of grains, number of grains per row, number of grains per ear, grain size, thousand grain weight and productivity. The macronutrient contents in the maize leaf at the beginning of flowering, the extraction and export of macronutrients were alsoevaluated. Regardless of the source of N employed, the productivity of maize grains increased until the dose of 160 kg of N ha-1. The export of N for the grains showed no difference for the studied sources. While it presented the highest export of N for grains at rate of 117,87 kg of N ha-1. The source urea showed greater total extraction of N compared to the source of ammonium nitrate, presenting greater extraction for the rate of 123,87 kg of N ha-1. The total extraction of calcium and magnesium was increased up to the dose of 160 kg of N ha-1.