Nitrogênio em cobertura no estudo de dois grupos de genótipos de milho em Gurupi-TO

The nitrogen is the most absorbed nutrient by maize, and its supply after seeding is common. However, its available for the plants is associate with soil and weather conditions and with kind of genetic material that is used, due the yield potential and the genetic base. This paper had the aim to evaluate two maize genotype groups at levels of nitrogen in covered, in Gurupi, Tocantins State, Brazil, season 2012/13. The experiments with 30 genotypes had two levels of covered nitrogen (0 and 150 kg ha-1) and they were seeding in two dates. The experiments with 12 genotypes had three levels of covered nitrogen (20; 80; 140 kg ha-1) and they were seeding in four dates. The experimental design was randomized blocks with three replications. For the analysis of variance, the experiments were clustering in accordance with the seeding date for the evaluation the effects of genotypes and covered nitrogen. In the two genotypes groups were not observed the significant interaction between the sources of variation. The leaf chlorophyll, between stages VT-R1, was the most sensible with the change of covered nitrogen level.