Production and Mineral Composition of Urochloa Brizantha Cv. Xaraes Fertilized with Nitrogen Sources.

In order to evaluate the effects of nitrogen doses and sources on the production of dry mass and mineral composition of Urochloa brizantha cv. Xaraés, a field experiment on soil classified as typical dystrophic red yellow latossol was performed in Araçatuba, São Paulo, Brazil. An experimental design in randomized blocks with three replications was used, in a 3 x 3 factorial scheme, being three nitrogen doses (100, 200 and 400 kg ha^-1 yr^-1) and three sources (Ajifer L40, ammonium sulfate and urea), plus a control treatment without addition of N. The nitrogen fertilization increased production of dry mass of the Xaraés grass with no difference among the sources which were studied. With linear equation of Liebig, it was observed that the inflection point was 25,431 kg ha^-1 of dry mass with 236.80 kg ha^-1 of nitrogen, representing 193% of the dry mass production obtained in the control treatment, noting that 85% of production refers to the rainy season. The Ajifer L40 and ammonium sulfate showed similar behavior in sulfur concentration in shoots of the forage, reaching foliar concentrations of 1.92 g kg^-1 and 2.16 g kg^-1 and in stems + sheaths concentrations of 1.89 g kg^-1 and 2.27 g kg^-1, respectively, both of which are important for the supply of the nutrient in pastoralist systems. With the use of urea the S concentration in leaves and stems was 1.61 g kg^-1. The decreasing order of nutrient uptake, in maximum production was K > N > Ca > Mg > P > S > Mn > Fe > Zn > B > Cu. In conclusion, for dry mass production, the sources showed the same positive response. However, the variation in mineral composition of the forage was due to the type of nutrients in the fertilizer.