Productivity and quality of Brachiaria brizantha B4 seeds in function of nitrogen doses.

This study aimed to evaluate aspects of reproductive phenology, yield components and seed quality of the B4 genotype of Brachiaria brizantha in function of nitrogen doses applied at pre-flowering. The experiment was carried out at Embrapa Beef Cattle, in a randomized block design, with seeding density of 2.59kg SPV ha-1 in the first year, in free growth plants. Urea was applied at pre-flowering at doses of 0, 25, 50, 75, 100, 125 and 150kg ha-1. The reproductive cycle of the plant lasts 225 days, with late flowering. N doses influenced the following characteristics: number of fully expanded inflorescences, percentage of dry matter, dry biomass, number of spikelets per raceme, seed yield, weight of a thousand seeds, germination, germination speed index, viability and germination at 10 months after harvest. The maximum yield of pure seed was 144.8kg ha-1 for 50kg ha-1 N, with maximum biological potential, based on components of seed yield of 456.27kg ha-1. Seeds presented high dormancy and reduced physiological quality in higher N doses.