Aduba？？o nitrogenada na cultura do milho safrinha irrigado em plantio direto

the second corn crop is an important economical alternative for agriculture. as this crop removes great amounts of n, it is necessary an appropriate nitrogen fertilization management for obtaining high yields. the objective of this work was to evaluate the effect of sources, doses and times of nitrogen application on agronomic characteristics and productivity of corn grains in an irrigated second crop. the experiment was accomplished in selvíria, mato grosso do sul state, in a red dystrophic latosol irrigated by sprinkle and conducted under no till, in 2007 and 2008. the experiment was arranged in randomized complete blocks design, with 4 repetitions, disposed in a factorial scheme 5x3x2, being: five doses of n (0, 50, 100, 150 and 200 kg ha-1), three sources of n (ammonium sulfonitrate with nitrification inhibitor, ammonium sulfate and urea) applied at sowing or totally at sidedressing in the stage of 6 leaves. the n sources provided similar grain yield. the nitrogen application at sowing was viable, as well as the traditional application of n at sidedressing. the increment of n doses increased the leaf n content, the number of grains per line and per ear and consequently the grain yield. the n doses increased the grain yield of the second crop up to 150 kg ha-1 of n, independently of application time or n sources.