DOSES AND SOURCES OF NITROGEN ON YIELD AND BROMATOLOGICAL COMPOSITION OF XARAÉS GRASS

Abstract

This study evaluated the effect of nitrogen sources and doses on dry matter yield and bromatological composition of xaraés grass throughout the year. The experiment was carried out at the Agronomy Faculty of Rio Verde University from October 2008 to January 2010. The experiment consisted of a randomized complete block design in a 2 x 4 factorial arrangement with measures repeated in time, and four replications. We tested two nitrogen sources (ammonium sulfate and urea) and four nitrogen levels (0, 200, 400 and 600 kg ha^-1). The evaluations were conducted on the same plots throughout the year and during all four seasons (autumn, winter, spring, and summer). The results demonstrated that the maximum grass production of dry matter and crude protein of xaraés grass for the sources of urea and ammonium sulfate were estimated at doses of 500 and 472 kg ha^-1 and 407 and 396 kg N ha^-1, respectively. And for TDN level the maximum dose was 404.74 kg ha^-1 N, for the source of ammonium sulfate. This result indicates that, regardless of the source, the application of increasing doses of up to 400 kg ha^-1 of nitrogen in xaraés grass is sufficient to maintain a high dry matter production, associated with the nutritional value of the forage. The source ammonium sulfate demonstrated higher efficacy for xaraés grass dry matter production in the seasons evaluated, however additional studies are needed to evaluate the economical feasibility of its use.

KEYWORDS: Ammonium sulphate; Brachiaria brizantha; urea; year season.