The high cost and the low efficiency of fertilizers, especially nitrogen (N), are of major concerns in agriculture. This study aimed to evaluate the effect of N fertilizers sources in Urochloa brizantha cv. Marandu (palisade grass). The study was conducted in Cerrado of Brazil to evaluate dry-matter yield (DMY), recovery of applied N (RAN), N use efficiency (NUE), and chemical composition of palisade grass in response to sources of N (ammonium nitrate, ammonium sulfate, ammonium sulfate-nitrate, urea, urea with urease inhibitor, polymer-coated urea, and control) in seven harvests (100 kg ha-1 N were applied after each harvest). The N fertilization increased DMY and growth of palisade grass compared to control (without N fertilization). However, there was not any difference in DMY due to N sources. Application of ammonium sulfate-nitrate increased RAN. The urea, urea with urease inhibitor, and polymercoated urea improved NUE. Concentration of neutral detergent fiber (NDF) was decreased, while concentrations of acid detergent fiber (ADF) and cellulose were not affected by the fertilizers. Crude protein (CP) content was increased with N supply, but CP fractions A and B were not changed, except in the fifth period of growth. The results indicated protected fertilizers (ammonium sulfate-nitrate, urea with urease inhibitor, and polymer-coated urea) are more recommended for the cultivation of palisade grass in the Cerrado biome of Brazil.

-The aim of this study was to evaluate dry matter yield and nutritional value of palisade grass (Brachiaria brizantha cv. Marandu) using nitrogen doses and sprinkler irrigation in two periods of the year, aiming at reducing seasonality of forage production. It was used a randomized block design in a split-plot scheme, with five doses of nitrogen (0, 50, 100, 150, and 200 kg/ha/cut), and the sub-plots were defined by the seasons of the year (wet and dry season), with and without irrigation. During the wet season, in the plots with and without irrigation, doses of 175 and 161 kg/ha/cut promoted the highest dry matter yields. During the dry season, 171 kg ha -1 N with irrigation resulted in the highest dry matter yield. During the same season, there was no response to N fertilization in the lack of irrigation. Average contents of CP were 10% with and without irrigation. Contents of neutral detergent fiber decreased with nitrogen doses, while acid detergent fiber was not affected by fertilization. Plots under irrigation reached the maximal acid detergent fiber content at N dose of 60 kg ha -1 . Irrigation promotes increase of 15% increase in dry matter yield and it increases contents of neutral detergent fiber.

Nitrogen (N) is the most limiting nutrient for growth of forage grasses, especially in conditions of low water availability. Therefore, it is important to evaluate the effect of N fertilization and irrigation on the accumulation of carbon (C) and carbon dioxide (CO2) by marandu grass in the Cerrado Paulista, in the rainy and dry seasons. Experiments were conducted to evaluate N fertilization in each season, with and without irrigation. Five N rates were used (0, 50, 100, 150 and 200 kg ha-1 per cutting), using urea as N source, totaling 0, 300, 600, 900 and 1200 kg ha-1 in the rainy season and 0, 100, 200, 300 and 400 kg ha-1 in the dry season. The experiments were arranged in a split-plot randomized block design. There was no significant interaction (p > 0.05) between N and time of fertilization in the irrigated experiment. However, N promoted a quadratic effect in organic matter production (OMP), accumulation of C and CO2 by marandu grass, while there was no influence of the seasons. In the non-irrigated experiment, the interaction between N rates and seasons was significant (p < 0.05) only for the rainy season. Organic matter production and C and CO2 accumulation was greater in the rainy season than in the dry season. Irrigation provided increases of approximately 20% in C and CO2 accumulation. The use of N and irrigation increases the accumulation of C and CO2 by marandu grass, and this increase is higher during the rainy season.