EXTRAÇÃO DE NUTRIENTES PELA FITOMASSA DE CULTIVARES DE Brachiaria brizantha SOB DOSES DE NITROGÊNIO

Abstract

Adequate amounts and balanced proportions of nutrient supply is fundamental for the forage productive process. For the fertilization handling, forage plant nutrient  requiriment must be known and, consequently, the plant capacity to extract soil nutrients. Therefore, the research had as objective to evaluate the nutrient extraction by Brachiaria brizantha phytomass under nitrogen doses. A randomized complete block experimental design with three replications in a plot repeated in time was used. In the plots, a factorial 3 x 4 arrangement was used, being three cultivars of Brachiaria brizantha (MG-4, Marandu and Xaraés) and four nitrogen doses (0, 50, 100 and 150 mg.dm-3). Three cuts of evaluation were allocated in time, referring.to the time of cuts. The source of nitrogen used was urea. The sharpest treatment effects on phytomass production of Brachiaria brizantha cultivars and nutrient extraction were influenced by the highest nitrogen doses. Xaraés-grass showed greater productivity in relation to the other cultivars, being.considered more responsive to the nitrogen fertilization. The maximum macronutrient extraction by Brachiaria brizantha followed the decreasing.order for the macronutrients: K > N > P > Mg.> S and micronutrients: Mn > Faith > Zn > Cu, being.necessary to restore soil nutrients, with the increase of nitrogen. KEYWORDS: Marandu, MG-4, nutrient absorption, Xaraés.