Structural and Production Characteristics of Piatã Grass Forage Submitted to Levels of Nitrogen

Abstract

Piat &atilde grass (Brachiaria brizantha cv. Piat &atilde ) is a tropical grass cultivating in pasture production system. The aim of this study was to evaluate the effects of nitrogen levels (0, 125, 250, 375 and 500 kg &middot N &middot ha ^-1 ) on structural characteristics and forage production of Piat &atilde grass. The experiment comprised of twenty grass parcels arranged in randomised completely casualties design. This study was carried out between November of 2007 and April of 2008, with 175 experimental days. A quadratic effect (P < 0.05) was verified for nitrogen dosage on canopy height, final leaf blade length and leaf area index. Nitrogen fertilisation altered the population density of tillers, with estimated maximum value of 955 tillers &middot m ^-2 at a nitrogen dose of 357 kg &middot ha ^-1 . A quadratic effect (P < 0.05) was also verified for nitrogen levels on the production of total and green leaf blade dry matter, with estimated maximum values of 19,253 and 11,548 kg &middot ha ^-1 &middot year ^-1 for nitrogen levels of 411 and 384 kg &middot ha ^-1 , respectively. However, a considerable portion of forage production obtained by nitrogen addition occurred from stem production. The productions of green leaf blade dry matter, tiller density, leaf blade length and leaf blade index are all variables related to structural aspects and pasture quality, with all attaining their highest values at a mean nitrogen application level of 380 kg &middot ha ^-1 .