Abstract

The aim of this study was to evaluate the performance of sources and application rates of topdressed nitrogen (N) on second-crop corn following soybean in an improved fertility Latossolo in the region of Campos das Vertentes, MG. Brazil. A randomized block experimental design was used in a 4 x 5 +1 factorial arrangement, with four replications. The treatments consisted of the combination of four N sources via forms of urea: conventional urea (common urea), urea coated with 16% elemental sulfur (Urea+S), urea treated with base compound urease inhibitor with a 0.4% boron and 0.15% copper (Ureia+B+Cu), urea treated with 1.060 mg kg^-1 of the urease inhibitor N-(n-butyl) thiophosphoric triamide (Urea+NBPT), and five application rates of N through urea: 30, 45, 60, 90, and 120 kg ha^-1, plus an additional treatment without N supplied in topdressing. The N concentrations in the leaves and grain, the exported N, the mineral N in the soil (nitrate and ammonium), grain yield, and profitability were evaluated. The N sources increased the N concentrations in the leaves, in the grain, and the exported N. However, the grain yield and the N concentration in the soil did not vary in accordance with the sources of urea. Increasing application rates of N increase N concentration in the leaves and in the grain, exported N, grain yield, and the mineral N concentration in the soil up to a depth of 10 cm. Application of N in topdressing is not economically beneficial considering the final yield of the second-crop corn following soybean in a soil with improved fertility.

Key words: Zea mays L, Urea, Nitrogen, No-tillage system, N rates.