This work was implanted in 1977 and conduced during four years at Experimental Estation of Goiânia, in a oxisol. It?s objetive was do determine the influence of rates and time of aplications of nitrogen upon productivity, quality and production components of seeds of braquiária grass. Considering soil analisis, a fertilization was done with 2t/ha of dolomitic, 400kg/ha of simple superphosphate and 70kg/ha of potassium chloride. The seedling was done at 07/11/77 in a furrows spaced of 0,40m, and spent 13kg/ha of seeds. The experimental design was a randomized block, with four replications, and the treatments was arranjed in factorial of 5 x 3 (five nitrogen rates: 0, 30, 60, 120 and 240kg/ha of ammonium sulfate; and three aplications time: second fortnight of january, first fortnight of february and second fortnight of february). The inflorescences was harvested by hand at 32 days after initial head emergence and dryed under shadow. The parameters analyzed were: seed production, yield of pure germinating seeds, yield of dry mater, seed germination, pure germinating seeds, seed emergence and head density. The analysis of data let to the conclusion that the better time to nitrogen fertiization was at the second fortnight of january, and the better rate of nitrogen from 120 to 150kg/ha.