Otimização azotada no capim-elefante para fins energéticos

An experiment was conducted without irrigation in randomized block design, in a split-split plot design under five levels of nitrogenand four levels of phosphorus with three replicates for each treatment, in Alegre (ES), to estimate fertilization levels of cultivars. A function of production was used to obtain the levels of physical maximun and optimal economics. The cultivars were integrated in the plots, phosphorus in the subplots and nitrogen were integrated in the subsubplots. There was no significance for phosphorus and their interactions. The other factors showed significance. Therefore, we performed another analysis involving Genotype and Nitrogen factors through statistical model split split plot in space. The estimated productivity (t ha-1) obtained a significant statistical adjustment (p < 0,05) to the second-order model for the surveyed cultivars. The results indicated positive responses to physical productivity depending on nitrogen fertilization.The net operating revenue was positive for Guaçu/IZ.2, Cameroon-Piracicaba and Cana D’África, whose values were 326.80 R$; 219.54 R$ and 281.49 R$, respectively, without nitrogen fertilization, because of the low grass price (41.82 R$ per ton) and the high nitrogen quote (2,670.00 R$ per ton). Thus, it can be concluded that there is a possibility to manage the production of elephant grass for energy purposes without the use of nitrogen fertilization.