Épocas de semeadura e características agronômicas de híbridos de milho irrigado cultivados com diferentes doses de nitrogênio

Abstract

The nitrogen applied to corn crop can modify the plant performance depending on the environment conditions. This hypothesis leads to the development of research to verify the corn sowing date and the amount of nitrogen applied, since the sowing date alters the corn development due to environmental factors. The objective of this study was evaluate grain yield at different sowing dates, and with the increase of nitrogen dosage. Two experiments were conducted at Pioneer s Corn Research Center at random experimental blocks design, with treatments set in a split plot arrangement with four replications. Experiment I was performed in 2005/06 season, and defined the nitrogen dosage influence of 0, 40, 80, 120, 160, 200, 240 kg ha-1, at the best sowing date for three corn hybrids. The different nitrogen dosages influenced the grain yield. To sowing performed in September the high nitrogen dosage increased grain yield, despite of a lower amount of nitrogen in the leaves and grain. Variables such as weight per thousand kernels and number of kernels per ear were also distinguished in the second sowing date. The second experiment was performed on 2006/07, and defined the nitrogen dosage influence (0, 40, 80, 120, 160, 200, 240 kg ha-1), to verify the best sowing date for an early maturity hybrid. The results were similar to Experiment I, with a higher grain yield and number of kernels per ear to September sowing date. October sowing date increased the leaf area index and reduced the nitrogen amount of leaves and grain