Nitrogen-use efficiency of maize genotypes in contrasting environments.

The purpose of this study was to evaluate the nitrogen-use efficiency of 15 corn hybrids in different environments. The experiment was conducted at the research station Embrapa Milho e Sorgo, in environments with low (12 kg ha-1) and high (120 kg ha-1) nitrogen fertilization, in a randomized block design with three replications. The chlorophyll content, leaf nitrogen and nitrate reductase activity in the flag leaf were determined at flowering and the grain yield was evaluated at harvest. The chlorophyll content proved to be sensitive to nitrogen availability, although without discriminating genotypic differences efficiently. To use nitrate reductase for this purpose, further studies are needed on the reliability of this biochemical variable to diagnose genotypes efficient in N use precociously. The hybrid L2xL3 was considered promising for maize breeding programs aimed at gene introgression related to N-use efficiency.