Morfogênese, parâmetros estruturais e produtividade em capim-pioneiro submetido a doses de nitrogênio

Abstract

The experiment was carried out at Experimental Farm of the Universidade Estadual de Montes Claros. UNIMONTES, in Janaúba county, from December 2010 to April 2011 in order to evaluate the effect of the nitrogen doses on the productivity, morphogenesis and structural characteristics of the elephant-grass cv. pioneiro. The experimental design was in randomized blocks with five replicates, totalizing 20 experimental units. The treatments were composed of four doses of nitrogen (100, 200, 300 and 400 kg.ha-1.year1 ). The experiment was kept under irrigation. Evaluative cuts were accomplished at 50 cm from the soil, as soon as the fodder plant reached the luminous interception of 95 %, without pre-defined intervals. The source of used nitrogen fertilizer was urea, applied at throw in each plot, fractionated, during the experimental period, soon after each cut. The relative medium values of evaluative cuts were used for effect of the statistical analyses. They were determined leaves eappearance rate, Phyllochron, leaves elongation rate, pseudostem elongation rate, number of alive leaves per tiller, population density of tillers, dry matter production and blade : pseudostem relation. According to the obtained results, it was observed that the nitrogen fertilization significantly increased the dry matter production per hectare, leaves appearance rate, leaves elongation rate, and pseudostem elongation rate and a negative lineal effect on the phyllochron, no presenting interference on the structural characteristics number of alive leaves, population density of tillers, blade pseudostem relation. The production, leaf appearance, leaf elongation and stem increased lineally until the highest applied dose, showing that the dose of 400 kg ha-1year-1 is the more indicate one for fertilization, however it is necessary a study on the economic viability of higher doses of nitrogen.