Estudo da eficiência de uso do nitrogênio em variedades locais e melhoradas de milho

Abstract

(Nitrogen use efficiency in local and improved maize varieties). The requirement of nitrogen fertilizers to increase crop productivity risks environmental contamination and increases farmer production costs up to 40% in maize cultivation. The objective of this study was to evaluate physiologic parameters related to nitrogen use efficiency and so contribute to maize breeding programs targeting grain yield in low-N environments. Three maize local varieties (Pedra Dourada, Catetão e Carioca), two improved varieties selected in fertily soil (BR 105 and BR 106) and two improved varieties selected under low N (Nitroflint and Nitrodente) were studied. Plants were supplied with Hoagland nutrient solution with two N levels in the form of nitrate (75%) and ammonium (25%). Low N plants were supplied with 1 mM of N and high N plants with 15 mM of N. The experiment, conducted in greenhouse, was carried out in complete randomized block design with three replicates and 14 factorial treatments. Nitrogen deficiency intensely decreased shoot growth and had a neglectful effect on root system. The biochemical traits studied (pigment contents, nitrate reductase and glutamine synthetase activities) were affected by N supply but did not show variability among genotypes. Dry matter accumulation in nitrogen deficient plants correlated positively (0.86) with the dry matter accumulation in the root system of maize genotypes. Our results suggest that the investigation of root properties may provide important precocious data about nitrogen use efficiency of maize genotypes.