Sources and dosages of Nitrogen applied with urea coated with polymers in Marandu Palisade Grass

Nitrogen is one of the most important nutrients for the production of forage grasses, and the most expensive one. The scope of this research was to evaluate the application of four sources of urea (conventional and coated with polymers) under different dosages, in mass production and nitrogen content and absorption from two cuts of Brachiaria brizantha cv. Marandu. The experiment was conducted at a greenhouse in a randomized block design. The fertilizers used were conventional urea, urea covered with a polymer layer, urea covered with sulfur and urea covered with a boron and copper compound. The dosages used were 30, 60, 90 and 120 kg ha(-1) of nitrogen. Fresh and dry mass, root weight and nitrogen content from first and second harvest were evaluated. On the first harvest, there was no significant difference between the treatments for the variables analyzed. On the other hand, second harvest presented difference in fresh and dry mass and nitrogen content. Regression analyses showed a linear increase with all fertilizers used, but this growth was more accentuated for the polymerized fonts. All polymerized ureas allowed higher mass production for Marandu palisadegrass, at tillering and second cut. Foliar nitrogen availability of polymerized ureas did not differ from conventional urea, being recommended to reach pastures with higher quality and productions and to decrease nitrogen losses on the system.