Avaliação nutricional de pastagem irrigada de capim tanzânia sob diferentes níveis de fertilização com fósforo e nitrogênio

Abstract

The objective of this work was to evaluate the nutritional value of Panicum maximum Jacq. cv Tanzania grown under irrigation area and different nitrogen (N) and phosphorus (P) doses in the North of Minas Gerais. The experiment was conducted in a sub-subdivided plots, being the phosphorus doses (0, 40, 80 and120 kg P2O5ha-1 year) in the plots, the nitrogen doses (0, 100, 200, 300 and400 kg Nha-1year) in the sub-plots and the seasons in the sub-subplots, in a randomized block design with three replications. The cuts were made every 35 days during the seasons of spring and summer, every 28 days in the fall and every 49 days during the winter, between September 2010 and September 2011, total of ten cuts. The samples were randomly collected from a 30 cm height in two square 1.0 x 1.0 m. The chemical composition and kinetic measurements of ruminal dry matter (DM) by the technique of in vitro gas production were analyzed. The cumulative yields of gases were analyzed in samples of spring, according to a split-plot experimental design, and the levels of phosphorus (0, 40, 80 and 120 kg ha-1 yr P2O5) in the plots and nitrogen levels (0, 100 , 200 and 400 kg N ha-1yr) subplots, in randomized blocks with three replications. The CP, NDF, ADF, LIG, Ca and P varied from 10.23 to 12.24%, from 70.74 to 74.98%, from 33.88 to 37.87%, from 4.07 to 5.19 %, 0.47 to 0.74% and 0.27 to 0.35% of respectively, depending on the fertilizer. The cumulative yields of gases were 11.6, 25.3, 61.4, 99.7, 116.2, 123.6 mL / g DM, for incubation times of 6, 12, 24, 48, 72 and 96 h, respectively. The average values of effective degradability of DM (EDDM) were 52.79, 47.69 and 43.04% per hour for the passage rates of 2.0, 5.0 and 8% per hour, respectively . There was no interaction between fertilizer and chemical composition, however, this was affected by the seasons. Kinetic parameters of ruminal fermentation and DEMS showed variations between treatments, however it was not possible to classify them.