RESUMO -O experimento foi realizado no período de dezembro de 2002 a abril de 2003, com o objetivo de avaliar, em capim-mombaça, o efeito de duas fontes de fósforo (superfosfato simples + superfosfato triplo e termofosfato magnesiano Yoorin®), em função dos dias (24) e da época de avaliação (verão e outono), sobre intervalo (IAPF) e taxas de aparecimento (TAPF), alongamento (TALF) e total de folhas senescentes (TFS), altura da primeira (HPLIG) e da última lígula (HULIG) e número de folhas expandidas (NFEX), em expansão (NFE), total de folhas (NTF) e total de folhas (24) and evaluation period (summer and autumn) on leaf appearance interval (LAPI), leaf elongation rate (LER), leaf senescence (TLS), first and last ligule height (FLH; LLH), number of expanded leaves (NEL), number of leaves in expansion (NLE), total number of leaves (TNL), total number of live leaves (TNLL), and grazing return rate (GRR) on mombaçagrass (Panicum maximum Jacq. cv. Mombaça). The experimental design was randomized blocks with three replications. There was no difference between phosphorus sources in all evaluated variables, except for leaf elongation rate, which was higher in tillers fertilized with the SPS+TSP treatment. Differences were found between evaluation periods, with summer showing higher leaf elongation rate and ligule height (first and last). The days evaluated indicated effect on first ligule height (FLH; LLH), number of expanded leaves (NEL), number of leaves in expansion (NFE), total number of leaves (TNL), total number of live leaves (TNLL), total number of senescent leaves (TLS), and grazing return rate (GRR). For days and period interactions only TNLL and TSL had positive linear correlations.Key Words: leaf growth, period, senescence, tillers IntroduçãoNa exploração racional, é relevante que a pastagem apresente persistência e alta produção, para que o animal possa expressar o seu potencial genético com a utilização de forragens de alto valor nutritivo (Peternelli, 2003).O fósforo está entre os elementos mais importantes para o vigor e desenvolvimento das plantas. O crescimento

This study aimed to assess forage production, animal performance, and the chemical composition of Tanzania grass pasture fertilized with 50, 100, 200, and 400 kg ha-1 of nitrogen. The variables analyzed were: leaf mass, daily accumulation rate, leaf/stem ratio, average daily gain, stocking rate, live weight gain per unit of area crude protein, neutral detergent fiber, and in vitro dry matter digestibility of leaves. The pasture management maintained the pasture height at 50 cm by using a continuous grazing method with the adjustment of stocking rate. The experimental design was a randomized block with three replicates. The leaf mass increased linearly in response to nitrogen, with an increase of 1003 kg (34%) observed between a nitrogen content of 50 and 400 kg ha-1. Nitrogen did not affect the average daily gain, but increased the stocking rate and live weight gain ha-1. The value of crude protein and neutral detergent fiber were higher with increased nitrogen levels, whereas the leaf digestibility did not affect nitrogen use. The comparison of 50 and 400 kg ha-1 levels indicated that there was an average increase of 19.2% in the leaf crude protein. The increased application of nitrogen fertilizer in Tanzania grass improved the chemical composition and animal performance; with regard to studied variables, the dose of 200 kg ha-1 resulted in the greatest improvement.