The objective of this study was to identify the rate of molybdenum that, associated with nitrogen fertilization, would provide the best responses on the vegetative structureof Mombasa grass. Forty days after planting, a uniform pruning was made when the established levels of molybdenum were applied and the experimental period started. The experimental design was a randomized block, with four replications (blocks), in a 5x6 factorial scheme, considering the combinations of treatments, the combinations of five levels of molybdenum (0, 50, 100, 150 and 200 g ha-1 year-1), in six evaluation ages (days 7, 14, 21, 28, 35 and 42 after pruning for uniformization) and four rates of nitrogen (0, 100, 250 and 500 of N. ha-1 year-1). The variables were subjected to variance analysis and adjustment in regression using orthogonal polynomials. Among the variables, an assessment of the number of leaves that were fully expanded (exposed ligula), in development or senescent in the main tillers (NFCE, NFEE and NFS, respectively) was carried out, as well as the total number of tillers per pot (NP) and the height of the vegetation (ALT). The rise in molybdenum supplies up to 200 g ha-1 increases the production of vegetative biomass of mombaça grass in pastures, by using levels of 500 kg ha-1 year-1 of N, but there is no difference between the other doses of nitrogen (0, 100 and 250 ha-1 year-1).

Keywords: Development. Tropical grasses. Intensive management of pastures. Pots.Biomass.