SWARD STRUCTURE AND TILLER CHARACTERISTICS IN PIATÃ GRASS PASTURES MANAGED WITH VARIABLE NITROGEN DOSES AND DEFERMENT PERIODS
Abstract This study was conducted from Feb. 25th, 2012 to Jul. 1st, 2012 to recommend nitrogen doses and deferment periods that result in deferred Brachiaria brizantha cv. Piatã (piatã grass) pastures with structural characteristics suitable for animal consumption. Combinations were evaluated between deferment periods and nitrogen fertilization conditions. The deferment periods were long (127 days) and short (79 days). Nitrogen doses were 0, 40, 80, and 120 kg/ha. The experimental design was a randomized block with three replications. The leaf area index (LAI) and light interception (LI) increased with the application of nitrogen. In the absence or at a small nitrogen dose, pasture deferred for short periods presented lower LAI and LI than pasture managed with long deferment period. The nitrogen only influenced the density of vegetative basal tillers. The lower deferment period resulted in a greater number of basal tillers and vegetative air, as well as fewer reproductive basal tillers. Nitrogen increased the length of the leaf blade and the vegetative tiller stem. Long deferral period resulted in longer stem and leaf blade and a larger number of dead leaves. Piatã grass can be deferred for 80 days, with application of 80 kg/ha of nitrogen at the beginning of the deferment period.