Effect of doses and timing of nitrogen application on agronomical traits of no-till corn

Maize is an important crop for grain production in the Center-West region of Brazil. An experiment was installed in Rio Verde (GO) in the 2002/03 growing season to evaluate the effect of doses and timing of nitrogen application on the agronomic traits of no-tillage maize. The experiment was evaluated as a 6 x 4 + 1 factorial in a randomized complete block design with 4 repetitions. The factors consisted of six nitrogen applications (before sowing; at sowing, top dressed 30 days after sowing, at sowing and top dressed 30 days after sowing; at sowing and top dressed 30 and 45 days after sowing, pre-sowing and at sowing and top dressed 30 days after sowing) and four nitrogen levels (25, 50, 100 and 150 kg ha(-1)), plus one control treatment without nitrogen application. The corn hybrid P30K75 and urea fertilizer were used. The dose of 150 kg ha(-1) led to the highest grain yield, nitrogen leaf concentration, grain weight per ear and plant height. The nitrogen leaf concentration was higher for applications in top dressing, at sowing and top dressed 30 days after sowing and at sowing and after top dressed 30 and 45 days after sowing. The nitrogen applications as top dressing (30 days) and split application (pre-sowing plus at sowing and top dressed 30 days after sowing) led to the highest kernel weight per ear and per 1.000 grains. The effect of dose or date of nitrogen application on protein yield and disease severity was not significant. The highest net profit was obtained with the application of 25 kg ha(-1) nitrogen at sowing.