Indicadores qualitativos e reservas orgânicas de Panicum maximum cvs. Quênia e Tamani, sob intensidades de pastejo

Abstract

The goalwas to evaluate the qualitative indicators and organic reserves of Panicum maximum cvs. Quênia and Tamani under grazing intensities. The experiment was carried out in a randomized complete block design in a factorial arrangement (2x2), with two cultivars: Tamani and Quênia guineagrass (Panicum maximum cvs BRS Tamani and Quênia) and two grazing intensities (high and low), as they defined a 15 and 25 cm post-grazing shade for Tamani guineagrass; and 20 and 35 cm for Quênia guineagrass with three replications and 12 experimental units (120m2 each), in six periods (autumn/spring/summer/15, autumn/spring/16 and summer /17). In each cycle, samples were taken for quantification of herbage accumulation (HA), morphological separation and chemical composition in pre-grazing. In the post-grazing, the residues and roots were collected to analyze organic reserves. Light interception (LI) and height measurements were done weekly in all regrowth cycles. In pre-grazing, the mean height was 35.5 for Tamani guineagrass and 55.6 Quênia guineagrass. Quênia guineagrass presented the highest HA in the aut/15, sum/16 and sum/17. Tamani guineagrass showed the highest HA in the sum/16 and sum/17. The highest leaf ratio in whole forage was found in the aut/15. Both grasses had a higher proportion of stem and dead material under high intensity. Quênia guineagrass in both intensities presented the highest levels of NDF in the seasons of greatest precipitation. The highest levels of CP were found aut/15, spri/15, sum/16 and aut/16. The upper stratum presented higher CP content, and the lower stratum had the highest content of NDF, ADF, NDF indigestible and LIG. The Tamani guineagrass showed higher root mass and N store. The low intensity promoted higher N store in the residues, and higher NSC values in roots and residues. The NSC content was higher in the residues and lower in the roots. The total N content in roots was higher in the spr/16 at both intensities. At low intensity, in the spr/16 the roots obtained higher total N content. The Quênia and Tamani guineagrass presented responses in forage production and nutrient value characterizedby climatic conditions. The cultivars have different structures, however, similarity in forage production and nutritive value, in both grazing intensities employed. The regrowth period must be respected (95% LI), providing the cultivars good forage production, maintaining the qualitative indicators and reducing the dependence of the organic reserves by the forage.