Studies evaluating tropical forages submitted to different types of fertilization are wide, but the productivity dynamics of Mavuno grass (Urochloa spp.) established in Quartzarenic Neosol are still few. The objective of this study was to evaluate the effects of topdressing nitrogen fertilization, in Mavuno grass pasture, on the productive and structural characteristics of the forage plant installed in sandy soil. The experimental design used was randomized blocks, with four treatments and five replications. The treatments are a control, without nitrogen fertilization; a single application of nitrogen in the first cycle (50 kg.ha-1 of N); two nitrogen applications, in the first and second cycles (50 kg.ha-1.cycle-1 of N, totaling 100 kg.ha-1 of N); three applications of nitrogen, in the first, second and third cycles (50 kg.ha-1.cycle-1 of N, totaling 150 kg.ha-1 of N). The productive cycles lasted 28 days, with 20 cm of crop residue. Canopy height (AD), total dry mass (MST), senescent material dry mass (MSMSen), leaf dry mass (MSF), stem dry mass (MSC) and leaf:stem dry mass ratio (F:C). There was difference in all variables of all treatments. However, some variables were similar between some treatments. As the number of nitrogen fertilization increases in the productive periods, there is an improvement in the productivity of Mavuno grass. This brought greater productivity not only for the variables of greatest interest (AD, MST and MSF) but also those less favorable to animal production (MSMSEN and MSC). The second cycle was spent with a higher rainfall (304.8 mm) compared to the first (152.5 mm) and third (76.9 mm) cycles and, consequently, a better productive period, which contributed to the treatment testifying, without N application, obtained AD, MST and MSF close to that produced by the treatment with two fertilizations in cover of 50 kg.ha-1.cycle-1 of N in the first and second cycles in the third productive cycle. Topdressing fertilization with the use of nitrogen in Mavuno grass, in Quartzarenic Neosol, enhances its production in optimal periods of rainfall. In drought periods, nitrogen fertilization contributes to greater forage production in sandy soil. The greater number of topdressing fertilization applications improves forage production and, consequently, produces less nutritious materials for the animals.
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