Productive potential of superior genotypes of Paspalum notatum Flügge in response to nitrogen fertilization

SUMMARY The Paspalum genus forms the natural pastures of the tropical and subtropical regions of America and includes several species of recognized forage potential. The aim of this study was to evaluate the influence of different levels of nitrogen fertilization on the agronomic traits and nitrogen use efficiency in superior genotypes of Paspalum notatum Flügge. Four nitrogen fertilization levels (0, 60, 180 and 360 kg N ha-1) and nine genotypes were evaluated, six from the United States Department of Agriculture (USDA) (30N, 36N, 48N, 70N, 83N and 95N), collected in South America, two native genotypes of Rio Grande do Sul, Brazil (André da Rocha and Bagual) and cv. Pensacola. The experimental design was a randomized complete block in a 4 x 9 factorial, with four field replications. From the variability of the responses found for the agronomic traits, the genotypes 48N, André da Rocha and Bagual are indicated to continue in the breeding program because they reach the maximum productive efficiencies according to the doses of N tested. The genotype 36N obtained the highest efficiency of nitrogen utilization, being biologically viable with the lowest N dose, equivalent of 60 kg of N ha-1