Dinâmica de acúmulo de forragem e parâmetros morfogênicos e estruturais de capim-marandu submetido a quatro alturas de dossel

Abstract

The study was carried out at Experimental Farm of the Universidade Estadual de Montes Claros (UNIMONTES) in Janaúba - MG, from July 2009 to May 2010, in order to evaluate the effect of different sward heights on the morphogenesis, forage yield and qualitative characteristics of the Marandu grass. The used experimental design was in randomized blocks (ERB) with five repetitions, totalizing 20 experimental units. The treatments corresponded to four sward heights: 30, 45, 60 and 75 cm. Based on analysis of soil was performed nitrogen fertilization after each cut at dosage of 50 kg N ha-1. The experiment was conducted under irrigated conditions. Three evaluative cuts were carried out as soon as the grass reached the desired sward height, without pre-determined intervals. The mean values for the three evaluative cuts were used for statistical analysis. The leaf appearance rate (LAR), phyllochron (PHY), leaf elongation rate (LER), pseudoculm elongation rate (PER), leaf lifespan (LL), senescence rate (SR), final length of leaf blade (FLLB), number of alive leaves per tiller (NALT), tiller density population (TDP), percentage of leaves (% L), percentage of pseudoculm (% C), dry matter production (DMP), dry matter content (% DM), rate of herbage accumulation (RHA), average weight of tillers (WT), crude protein (% CP), NDF content (% NDF), ADF content (% ADF), lignin content (% LIG), leaf area index (LAI) were determined. Linear increases in function of the sward heights were observed for the variables PHY, PER, LL, SR, FLLB, NALT, % C, DMP, % DM, RHA, WT, % NDF, % ADF, % LIG, LAI; while LAR, LER, TD, %L were decresead with the treatments.. In function of the obtained results, it is possible to conclude that the cutting of Marandu grass at sward height between 45 and 60 cm presents appropriate values of production and nutritional value without compromise the persistence of forage.