The morphogeneticand structural traits of Brachiaria brizantha cv. Xaraés submittedto the treatment combinations of four nitrogen rates (0, 40, 80 and 120 mg/dm3)and three defoliation frequencies (two, four and five completely expanded leaves)were evaluated according to a 4 x 3 factorial arrangement. The experiments wereconducted in a greenhouse, with the treatments arranged as factorial combination.The experimental design was completely randomized, with four replications. Afterthinning, three seedlings were left per pot (5,8 dm3). The phosphate fertilizationwas performed according to the soil fertility. The pots were fertilized withphosphorus and potassium, according to soil fertility. Nitrogen fertilizationwas split in four applications and applied in aqueous solution. When the plantsreached the number of expanded leaves (defoliation moment), they were cut at5 cm height from soil level before evaluation of morphogenetic and structuraltraits in the aftermath. Significant nitrogen effect was observed on morphogeneticand structural characteristics of xaraésgrass and on DM yield, excepton root DM. Leaf elongation rate (LER) increased linearly up to 37% at the Nrate of 120 mg/dm³. Defoliation influenced leaf elongation rate, phyllochron,blade length, number of live leaves per tiller, senescence rate and dry matteryield of shoot and root.
