LEONARDO RICARDO ROTTA
Abstract:
The experiment was conducted at Jataí Campus, UFG, aiming to evaluate five nitrogen doses (0, 80, 160, 240, 320 kg N / ha) in dry matter (MS) and crude protein (PB) production and MS contents, CP, neutral detergent fiber (FDN) and acid (FDA) of andropogon, brachia decumbens, pioneer and mombaça grasses in 2x5 factorial two-factor (1: andropogon vs. brachia decumbens and Factor 2: pioneer vs. mombaça) grasses, with five repetitions and four cuts. Data analyzed and means compared by orthogonal contrasts by the 5% F test for dose. In factorial 1 there was interaction (P <0.05) between species and dose for MS and FDA and MS production and difference between species and doses for CP and mean production of CP and MS, and only between species for FDN. Andropogon responded linearly to N doses for PTMS and cubically for FDA, with average yield increase of 5.56 t/ha and fiber content reduction of 11.76%. Andropogon presented FDN 4.6% higher than decumbens (81.46%). The average production of andropogon was 0.62 t/ha higher than decumbens (3.58 t/ha). Decumbens PB was 0.92% higher than andropogon (8.42%) and associated with DM production resulted in an average yield of 0.328 and 0.362 t CP/ha, respectively for the brachiaria and andropogon. Nevertheless, the brachiaria was more responsive to N rates than andropogon, reaching 10.63% PBMS when fertilized with 320 kg N/ha, while andropogon reached 8.87%. In factorial 2 the results show that nitrogen fertilization provided higher CP content for forage with variation from 8.32 to 10.63% in mombaça grass and from 11.94 to 12.77% in pioneer grass. yield of 0.330 and 0.578 kg PB/ha respectively. The increase in N supply also reduced mombaça grass FDA content from 28.79 to 17.03%. Among the two species, the pioneer grass was the most productive with total production of 25.71 t MS/ha (4.62 t MS/ha/cut), being 37% more productive than mombaça, which produced 16 .18 t MS/ha (3.58 t MS/ha/cut). In more extensive management systems the brachiaria decumbens is more responsive to nitrogen fertilization, producing grass with better nutritional value. When very demanding species such as pioneer and mombaça grasses are used, annual nitrogen doses above 240 kg / ha are required to maintain the productive capacity of the grass with the best nutritional value.
