Características produtivas, morfogênicas, estruturais e químicas dos capins piatã e paiaguás adubados com composto orgânico

Abstract

The use of organic compound in fertilization of pastures is a form of recycling nutrients contained in waste, and reducing chemical fertilizers. To perform pasture fertilization, however, it is necessary to know grass responses to doses of organic compounds. Thus, the objective of this study was to find the best dose of egg-producing poultry organic compound to maximize the productive, morphogenetic, structural, and nutritional responses of Paiaguás and Piatã grasses. A completely randomized design in a factorial 4 x 2 was used, composed of organic compound doses (0, 400, 800 and 1200 kg equivalent N.ha-1) and two cultivars of Urochloa brizantha (Piatã and Paiaguás), with three replicates per treatment, assessed during four successive cuts. The parameters evaluated were dry matter yield (DM) of shoots and roots, leaf appearance rate (LAR), leaf elongation rate (LER), phyllochron, pseudoculm elongation rate (PER), final leaf length (FLL), the number of green leaves (NGL) and senescence rate (SR). The nutritional value of the grasses was also assessed through contents of dry matter, organic matter, crude protein, neutral detergent fiber, acid detergent fiber, cellulose, hemicellulose, lignin, and "in vitro" organic matter digestibility. DM yields of both shoot and root increased due to nitrogen increase, and the Paiaguás grass presented the highest yields (P <0.01). The best organic compound doses ranged from 640 to 950 kg of equivalent N.ha-1 for most morphogenic and structural grass characteristics. The chemical composition of grasses was not influenced (P>0.05) by doses of organic compound. Levels of 8.05% CP, 67.10% NDF, and 65.14% IVOMD were observed for cultivar Paiaguás, while for cultivar Piatã these values were 7.58% CP, 70.32 % NDF, and 63.38% IVOMD. It is concluded that high doses of an organic compound are required (in equivalent N) for cultivars to reach the highest growth rates, and that Paiaguás grass has the highest dry matter yield, higher growth rates and better chemical composition when compared to Piatã grass, in similar organic fertilization conditions.