Características morfogênicas, estruturais e acúmulo de forragem do capim Panicum maximum cv. Tanzânia submetido a intensidades e freqüências de pastejo

• Autor(a) principal: Zanine, Anderson de Moura
• Data de Publicação: 2007
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/1902
• topic: Capim; Manejo; Morfogênese; Freqüência; Intensidade; Forage; Grass; Management; Morphogenesis; Frequency; Intensity; CNPQ::CIENCIAS AGRARIAS::ZOOTECNIA::PASTAGEM E FORRAGICULTURA

Grazing management should optimize forage accumulation, in order that most of the growth structures, such as leaves and culms, are harvested in a stage of development not to jeopardize the animal performance, as well as to minimize losses by senescence processes. Management strategies establishing pre- and post-grazing heights should therefore be studied, in order to set goals to minimize losses and guarantee pasture permanence. The experiment was carried out in area of the Animal Science Department at the Federal University of Viçosa, Viçosa, Minas Gerais, from November 2005 to October 2006. It aimed at evaluating morphogenic and structural characteristics, dynamics of tillering and forage accumulation of Tanzania grass (Panicum maximum) under different frequencies and intensities of grazing. The treatments consisted of combinations of two intervals between grazing periods based on light interception (LI) by the canopy during regrowth (90 and 95% LI) and two defoliation intensities (postgrazing heights of 30 and 50 cm), using the mob grazing technique. They were allocated to the experimental units (paddocks) following a 2 x 2 factorial arrangement, in a complete randomized block design, with three repetitions, making up 12 experimental units, and were termed (90/30, 90/50, 95/30 and 95/50). Pre and post-grazing heights, mass and forage accumulation and morphogenic and structural characteristics of the pastures were evaluated. The evaluations in the marked tillers were carried out right after grazing and in successive three-day intervals. Pasture height in pre-grazing was homogeneous and not varying much, with values close to 65 and 75 cm for 90 and 95% of LI respectively. Pastures managed at 50 cm post-grazing height showed larger number of grazing cycles (7,5) than pastures managed at 30 cm (6,5), because of the shorter intervals between grazing. However, the larger number of grazing cycles was not enough to compensate for the smaller crop efficiency in those treatments, leading to lower forage accumulation at the end of the experimental period. The morphogenic and structural characteristics were affected by the seasons of the year. Leaf elongation rate and leaf appearance rate in the summer was 2,5 times higher than those recorded in the fall and winter/beginning of spring. Besides season effects, the post-grazing height effect was also observed, which was responsible for the largest tiller renewal during the summer. The highest forage accumulations occurred in the treatments 95/30 and 90/30. This superiority was mainly consequence of the high accumulation of leaf blades, mostly in the end of spring and summer. Considering the largest mass and forage accumulation, the largest percentages of leaf blades and lower participation of dead material, and stability of tiller population, the grazing management of Tanzania grass under rotational stocking should be done when 95% of the incident light is intercepted, that is to say, a pre-grazing height of 75 cm and the removal of the animals with post-grazing height of 30 cm. When the pastures reach a condition very close to grazing (70 cm height), it is possible to adjust the management allowing the animals into the paddocks a little earlier, with 90% of LI or 65 cm height, without impairing pasture production and roductivity.