-Nitrogen (N) is one of the nutrients that have the most significant effect on corn grain productivity increase. In order to evaluate the effect of sources of N topdressing and doses in the grown corn culture, in a conventional till system, it was installed an experiment in the city of Urutaí, Goiás, in the 2012/13 crop, in clayey textured Red Latosol. The experimental design was a randomized complete block design with four replications, with the treatments arranged in a factorial 3 x 5, consisting of three sources (coated urea, urea and ammonium sulfate) and five doses (0, 60, 120, 180 and 240 kg ha -1 ) of N, topdressing, applied in the surface and in a single dose, when the corn plants were in V 4 stage. The hybrid used was the P3646H. We evaluated the following characters: stem diameter, plant height, height of ear insertion, leaf N, number of ears per plant, ear length, number of rows per ear, number of grains per row, 100 grains mass and grain productivity. All characters have a response to nitrogen fertilization and only the height of ear insertion showed no significant difference between sources. The source coated urea showed the best results, indicating that its use may be compensatory, especially in favorable conditions for the NH 3 volatilization, as the application of high doses of N in the surface.

Submetido em 18/03/2014 e aprovado em 17/07/2015.

The objective of this study was to evaluate the different timing, methodsof applicationand nitrogen doses in the agronomic characteristics, production components, grain yield, as well as the nutrient utilization efficiency in the maize crop. The experimental design of randomized blocks, in a factorial scheme (2 x 2 x 4) and four replicates, was used for the experiment. The treatments were two application times, (maize sowing and in V7 stage coverage); two forms of application(superficial and incorporated to the soil at 8 cm depth); and four nitrogen doses (0, 60, 120, 180 kg ha-1). The agronomic characteristics of corn, plant height, spike insertion height, stalk diameter and leaf nitrogen did not differedaccording to the seasons or the application forms, only the nitrogen doses. The components of the production, length and numberof rows per spike, number of grains per row, mass of 100 grains and grain yield presented better results with application of the nitrogen incorporated in the soil and doses of 120 to 180 kg ha-1of nitrogen. The incorporation practice and the 60 kg ha-1dose provided greater agronomic efficiency in the use of nitrogen.

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