Acúmulo de forragem e parâmetros morfofisiológicos de Pennisetum purpureum Schum. Cv Pioneiro, submetido a diferentes alturas de resíduo e interceptações luminosas

Abstract

The experiment was carried out at Experimental Farm of Universidade Estadual de Montes Claros (UNIMONTES) in Janaúba disctrict, Minas Gerais, from November 2008 to June 2009 in order to evaluate the effect of interactions between two stubble heights (30 and 50 cm) and two light interceptions (95 and 100%) on morphogenetic, structure, production and bromatologic characteristics of Pennisetum purpureum Schum. cv.Pioneiro. The experimental design was in randomized blocks (RBD) with four replicates (treatments 30/95, 30/100, 50/95 and 50/100), totaling 16 experimental units. The area fertility was kept with saturation at 70%. In the covering fertilization were applied 50 kg ha-1 of N after each cut, including those one in standardization. Irrigation was performed three times a week with 18,88 mm per square meter in each one. The morphogenetic variables in three basal tillers marked in each plot. The tiller population densities, were evaluated in marked area in all of the experimental units. The moments of the cuts were defined when the four plots of each treatment reached its pre-established light interception (95 or 100%). Once found the cut time, three herbage samples were collected per plot, by cutting the it within an area of 0.25 m2 for each sample. Those samples were collected at stubble height level proper of the treatment (30 or 50 cm). After that, they were submitted to bromatologic and productivity analyses. For purposes of statistical analysis, were used the mean values for the cycles between cuts throughout the experimental period, aiming to know different means between seasons. The interaction between the factors influenced significantly (P0.05) the variables Leaf senescence rate, Number of senescent leaves per tiller, Number of basal tillers, Number of aerial tillers, Total number of tillers, and values of Neutral detergent fiber, Acid detergent fiber, Hemicellulose, Cellulose, Lignin and Crude protein in the portions Leaves, Total (pseudoculm + leaves) and pseudoculm. It was observed most of variables being affected by interactions between the factors, they also influenced yield per area by time interval, allowing to define the treatment with stubble height of 50 cm and cutting to reach values about 95% of light interception (50/95) those with the best results.