Balanço dos nutrientes e do carbono em pastagens com diferentes níveis de intensificação da produção de leite no trópico úmido brasileiro

Abstract

To evaluate the effect of increased milk production system in the extraction and return of macros and micronutrients this study was conducted. The experiment was started in 2009 with four of milk production systems in Mombaça grass pastures (Megathyrsus maximus) during the rainy season. A completely randomized design with four replications (paddocks) and factorial arrangement of 2 x 2 (two nitrogen doses with and without concentrate supplementation to grazing animals) was used. Nitrogen doses corresponded to 400 and 800 kg ha-1.year-1 and supplementation was only used for two of the four groups of animals had higher milk production 11 L.dia-1. 48 cows with no racial pattern set were used to reduce the pasture to the recommended residual LAI, 32 test and 16 balance. Were evaluated the levels of N, P, K, Ca, Mg, S, in addition to Cu, Fe, Mg and Zn of green leaf blades (GLB), green stem (GSB), dead material (DMB), litter decomposition (LDEC) and faeces. The Samples of the GLB harvested pasture were also analyzed for their nutritional value. Levels were quantified, CP, Ash, EE, NDF, ADF, lignin, total carbohydrates and their fractions A + B1, B2 and C. The pastures managed with higher nitrogen dose increase the extraction of all analyzed macronutrients, with the exception of sulfur. The litter decomposition is the main source of return for the nutrients in the pasture, especially calcium, phosphorus and nitrogen. The dose of 800 kg N ha-1 year-1 reduced the zinc content in GLB and copper content in the GSB. By contrast, the zinc levels had higher concentrations in the litter in degradation with the higher dose of N. Supplementation, increased levels of iron and zinc in the faeces. The more intensified systems showed higher CP levels, lower levels of ADF, MM and total carbohydrates. Intensifying the use of nitrogen improved the quality of Mombaça grass pasture.