Canopy structure and forage nutritive value of elephantgrass subjected to different stocking rate and N fertilization in the "Mata Seca" ecoregion of Pernambuco

Abstract

The objective was to evaluate the effect of three stocking rates (2, 3.9, and 5.8 animal units ha-1) and three fertilization levels (0, 150, and 300 kg N ha-1 yr-1) on herbage mass and nutritive value of elephantgrass (Pennisetum purpureum Schum.) cv. IRI-381. The experiment was conducted from May to August of 2009 and 2010 in Itambe, PE, Brazil, during the rainy season. Treatments were allocated in a split-plot arrangement in a completely randomized block design. The variables measured included leaf mass (pre-and post-grazing), botanical composition, soil cover, leaf area index, light interception, leaf angle, and concentrations of dry matter, organic matter, N, and in vitro digestible dry matter. When fertilized with 300 kg N ha-1 yr-1, leaf mass reached 18,560 kg ha-1. Leaf area index decreased with increasing stocking rate. The relationship between sward height and light interception was R2 = 0.0126. Increased stocking rate resulted in greater contribution of signalgrass [Brachiaria decumbens (Stapf.) R.D. Webster] in the botanical composition, with a contribution up to 29% in 2010. Elephantgrass nutritive value is directly affected by the fertilization levels and stocking rate, with highest nutrient concentrations observed with 2 AU ha-1 and 300 kg N ha-1 yr-1.