Características morfogênicas, estruturais e composição química de capim-aruana submetido à adubação nitrogenada

Abstract

The experiment was carried out at the Federal University of Recôncavo da Bahia, with the objective of quantifying the morphogenetic, structural and chemical composition of the aruana grass, submitted to nitrogen doses. Twelve plots of Arauana grass were planted, with a useful area of 100 m2, which treatments consisted of four doses of nitrogen fertilization: 0; 75; 150; and 225 kg ha-1 of N, distributed in a randomized complete block design with three replicates. The morphogenic and structural characteristics were measured twice a week using a millimeter ruler, during all experimental period, in twelve tillers randomly marked by experimental unit. Nitrogen fertilization did not influence (P>0.05) the rate of expanded leaves and the rate of leaf expansion, presenting, respectively, mean values of 5.15 and 1.60 leaves / tiller. Leaf appearance and elongation rates, leaf blade final length; number of leaves total; and leaf dry matter production of the aruana grass were influenced by the nitrogen rates, adjusted to a quadratic equation (P<0.05). A negative linear behavior (P<0.05) was observed for N rates over the phyllochron, where the values ranged from 30.41 days for plants without fertilization to 16.71 days with 225 kg ha-1 of N. The duration leaf life was affected as a negative quadratic manner (P<0.05), by nitrogen doses. The height of stem increased linearly with the dose of nitrogen. Nitrogen fertilization exerts a positive effect on the morphogenic and structural characteristics, favoring higher yields of aruana grass, but the doses used N were not sufficient to affect the chemical composition, which is associated with forage quality.