Estrutura do dossel, demografia do perfilhamento e acúmulo de forragem em pastos de Brachiaria humidicola submetidos a regimes de lotação intermitente

• Autor(a) principal: Vilela, Hélio Henrique
• Data de Publicação: 2011
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/1789
• topic: Plantas forrageiras; Regimes de lotação; Pastos; Forage plants; Stocking system; Pastures; CNPQ::CIENCIAS AGRARIAS::ZOOTECNIA::PASTAGEM E FORRAGICULTURA

The objective of this experiment was to evaluate the sward structural characteristics, tillering demographics and forage accumulation in Brachiaria humidicola cv. Comum managed under continuous stocking. The experiment was carried out in the Forages sector of the Department of Animal Science at Universidade Federal de Viçosa, in Viçosa, MG, Brazil, from December 2009 to December 2010. The experimental design utilized was of completely randomized blocks with three replicates, in a 2 × 2 factorial arrangement. Four treatments, represented by two grazing intensities (post-grazing heights of 8 and 16 cm) associated to two defoliation frequencies (when the sward intercepted 95 or 98% of the incoming light) were evaluated. Thus, treatments were set as follows: 95/8; 95/16; 98/8 and 98/16. The incoming light interception (LI) and the sward height were monitored weekly. Sward structural characteristics, tillering demographics and forage accumulation and morphological composition were evaluated. Mainly in the paddocks managed at 98% LI, it was not possible to reach the post-grazing heights desired, which were significantly above those pre-established. The sward pre-grazing height, associated to 95% LI was, on average, 30 cm, whereas the height associated to 98% LI was, on average, 30 cm. The management of the pasture at 95% LI, because of the lower interval between grazing cycles - which varied from 29 days in the summer to 124 days in the fall/winter/beginning of the spring -, promoted greater grazing in comparison with the management at 98% LI, whose interval between grazing cycles varied from 76 days in the summer to 247 days in the fall/winter/beginning of the spring. Leaf appearance and tiller mortality rates were affected by grazing frequencies and intensities and by the seasons of the year, causing variation in the tiller population density. Thus, the tiller population density was higher during the summer and in the paddocks managed at 95% LI and 16 cm postgrazing height, showing the influence the frequency and intensity of grazing exert on the variables which determine it. The total forage accumulation during the experimental period was of 10000; 7320; 12270 and 7590 kg/ha DM for treatments 95/8; 95/16; 98/8 and 98/16, respectively. Paddocks managed at 98% LI presented lower proportion of leaf blades and higher proportion of stems in the forage in relation to those managed at 95% LI, which presented greater proportion of leaves and lower proportion of stems. The pre-grazing heights were linked to the light interception by the sward, so this characteristic could be utilized in a practical and reliable way. Because of the considerable forage accumulation, the greater leaf blades proportion in the forage and the maintenance in the stability of the tiller population, the most recommended defoliation strategy for Brachiaria humidicola cv. Comum under continuous stocking system would be the interruption of regrowth (beginning of the grazing period) when the sward intercepted 95% of the incoming light; a condition in which the pastures were 30 cm tall, and the end of the grazing when the pastures reached 16 cm post-grazing height.