Características morfogênicas, estruturais, acúmulo de forragem e composição química de capim-massai, submetido à adubação nitrogenada

Abstract

The objective of this study was to evaluate the morphogenic, structural, biomass accumulation and chemical composition of plants of Massai grass submitted to six nitrogen doses (0, 100, 200, 300, 400 and 600 kg of N / ha / year) in a completely randomized design, with six replications in plots of 12 m². Urea was used as the Nitrogen source, whose doses were divided in six applications during the rainy season, according to the treatments. Forage harvesting was done at a residue height of 15 cm, when the canopy intercepted 95% of the incident light at an average of five internal points on the plot with the Accupar model LP-80® canopy analyzer. Data were submitted to variance analysis and regression, the significance level was 0.05 of the linear and quadratic coefficient and the coefficient of determination. There was (p<0.05) an increase in the rates of appearance, length and leaf senescence, as we as the number of alive leaves, number of matura leaves, percentage of stems and number of grazing cycles, all of them adjusted to a linear model. In contrast, the phyllochron, the duration of the leaf's life, the leaf blade/stem ratio and the rest days decreased, also linearly adjusted. The results for the accumulation of forage per cycle, daily forage accumulation, total forage accumulation and accumulation of dry leaf mass corresponded in quadratic form (p<0.05), the increase of nitrogen fertilization means a direct effect of the nitrogen flow in the tissues. There was a positive and linear effect of the nitrogen fertilization (p<0.05) for the crude protein and organic matter content. Negative effect (p<0.05) adjuted to a linear model for the dry matter and mineral content. No effect was observed (<0.05) for neutral detergent fiber, acid detergent fiber and hemicellulose, which limit the digestion. The nitrogen fertilization favors morphogenesis, forage production and the qualitative characteristics of Massai grass.