ADUBAÇÃO NITROGENADA E P ARTIÇÃO DE MASSA SECA EM PLANT AS DE Brachiaria brizantha cv. XARAÉS E Panicum maximum X Panicum infestum cv. MASSAI Nitrogen fertilization and dry matter partition in xaraes grass and massai grass

. Dezoito dias apos a transplantacao realizou-se o desbaste, deixando-se tres plantas/vaso. Quando as plantasatingiram altura media de 35 cm foram submetidas a um corte de uniformizacao a 5 cm do solo. A adubacao nitrogenada foi fracionadaem 4 aplicacoes, e apos quarenta e cinco dias em crescimento livre, as plantas foram colhidas e avaliadas quanto aos teores de MS dalâmina, colmo, material morto e raiz. Avaliaram-se tambem as razoes parte aerea:raiz e lâmina:colmo. O nitrogenio exerce efeito naparticao de MS de plantas de capim-xaraes, favorecendo o desenvolvimento da parte aerea, sem efeito no sistema radicular. Observou-se tambem que o nitrogenio favorece a relacao lâmina:colmo, alem de acelerar o processo de senescencia nessas plantas, comconsequente aumento na deposicao de material morto.Termos para indexacao: Forrageiras, nitrogenio, parte aerea, raiz.ABSTRACTThe experiment was carried out in a greenhouse with the objective of evaluating the dry matter partition of capim-xaraes(Brachiaria brizantha) and capim-massai (Panicum maximum x Panicum infestum) submitted to four treatments of nitrogen (0, 40,80, and 120 mg/dm3). A randomized design with four replications was applied. Both species were sowed in trays containingcommercial agricultural substratum and 15 days after the emergence of five plants they were transferred to 5.8-dm3 vases. When theplants reached an average height of 35 cm, they were cut 5 cm from the soil to achieve a uniform cut. The nitrogen was applied fourtimes. After forty-five days of free development the plants were cut and evaluated for dry matter of the leaf, stem, dead material, androot. The shoot to root and lamina to stem ratios were also evaluated. It was observed, according to the results that the nitrogenaffected the dry matter partition of capim-xaraes, favoring the development of the shoot, but without effect on the roots. The totaldry matter production of xaraes and massai shoot, as well as the lamina to stem ratio increased linearly with the doses of N, withoutaffecting the root dry matter. It was also observed that nitrogen favors the lamina to stem relation and increases the dead materialdeposit in xaraes grass and massai grass.Index terms: Brachiaria brizantha, greenhouse, nitrogen, Panicum maximum