Produção de forragem, características morfogênicas e estruturais de capim-braquiária sob adubação nitrogenada

Abstract

The experiment was conducted at the Experimental Farm of the Empresa de Pesquisa Agropecuária de Minas Gerais (EPAMIG), located in the municipality of Felixlândia in the west center of Minas Gerais (latitude 18 º 15 'S and longitude 44 º 55' E, altitude 614 m) from December 2011 to May 2012. Treatments consisted of four nitrogen levels: 100, 200, 300 and 400 kg ha-1 year1 of N as urea, divided into two applications during the rainy season (January to March 2012) and a control treatment, without fertilization. The experimental design was in randomized block with four replications, totaling 20 plots. The dry matter accumulation rate was obtained by the ratio between the dry matter yield and the number of days of the trial period. The determination of the N use efficiency (NUE) by the fodder plant was obtained by subtracting the production of treatment without nitrogen by total dry matter yield (DM kg ha-1) from each treatment with N. The difference of production was divided by nitrogen level used into the respective treatment. A clump was selected randomly throwing a square 0.25 x 0.25 cm in each plot to determine the total density of tillers, generating the data of total basal and aerial tillers of the plot. They were marked two basal tillers per plot (total of 40 tillers) at random in different clumps, for evaluation of the morphogenic and structural canopy traits during grass regrowth. The obtained means were subjected to analysis of variance and Dunnett's test with 5 % confidence by SAS. For discrete quantitative variables, were tested by the General Linear Models (GLM) of the SAS. There were no significant differences for dry matter (P> 0.05) and morphogenetic variables: rate of leaf appearance, phyllochrono, leaf elongation rate, rate of elongation stem, leaf senescence rate and duration of life of sheet. There was an increase of total crude protein, the crude protein of the leaves and a decrease of the total neutral detergent fiber with the N levels (P< 0.05). The effect of N rates on the ratio Blade : stem and the percentages of leaf, stem and dead material was not significant (P> 0.05) and the leaf area index and the final length of the stem iThe experiment was conducted at the Experimental Farm of the Empresa de Pesquisa Agropecuária de Minas Gerais (EPAMIG), located in the municipality of Felixlândia in the west center of Minas Gerais (latitude 18 º 15 'S and longitude 44 º 55' E, altitude 614 m) from December 2011 to May 2012. Treatments consisted of four nitrogen levels: 100, 200, 300 and 400 kg ha-1 year1 of N as urea, divided into two applications during the rainy season (January to March 2012) and a control treatment, without fertilization. The experimental design was in randomized block with four replications, totaling 20 plots. The dry matter accumulation rate was obtained by the ratio between the dry matter yield and the number of days of the trial period. The determination of the N use efficiency (NUE) by the fodder plant was obtained by subtracting the production of treatment without nitrogen by total dry matter yield (DM kg ha-1) from each treatment with N. The difference of production was divided by nitrogen level used into the respective treatment. A clump was selected randomly throwing a square 0.25 x 0.25 cm in each plot to determine the total density of tillers, generating the data of total basal and aerial tillers of the plot. They were marked two basal tillers per plot (total of 40 tillers) at random in different clumps, for evaluation of the morphogenic and structural canopy traits during grass regrowth. The obtained means were subjected to analysis of variance and Dunnett's test with 5 % confidence by SAS. For discrete quantitative variables, were tested by the General Linear Models (GLM) of the SAS. There were no significant differences for dry matter (P> 0.05) and morphogenetic variables: rate of leaf appearance, phyllochrono, leaf elongation rate, rate of elongation stem, leaf senescence rate and duration of life of sheet. There was an increase of total crude protein, the crude protein of the leaves and a decrease of the total neutral detergent fiber with the N levels (P< 0.05). The effect of N rates on the ratio Blade : stem and the percentages of leaf, stem and dead material was not significant (P> 0.05) and the leaf area index and the final length of the stem.