Perfilamento em pastos de capim-mulato submetidos a estratégias de pastejo rotativo

• Autor(a) principal: Pena, Karine da Silva
• Data de Publicação: 2010
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/1773
• topic: Morfogênese; Acúmulo de biomassa; Interceptação luminosa; Alvo de manejo; Morphogenesis; Accumulation of biomass; Light interception; Target management; CNPQ::CIENCIAS AGRARIAS::ZOOTECNIA::PASTAGEM E FORRAGICULTURA

Tillers are considered units of growth of forage grasses, thus a pasture can be regarded as a population of tillers. In order to make them perennial and persistent there must be a balance between tiller appearance and death in pastures throughout the year. This dynamic between tiller appearance and death allows the pasture to adapt to different management conditions. The persistence of the pasture depends on the ability of the plants to renew and replace their tillers keeping the plant population stable. This, in turn, is determined by seasonal weather changes and by management strategies used. This way, this study was to evaluate tiller population density, tiller dynamics and stability of tiller population of mulato grass swards subjected to strategies of rotational stocking management. This experiment was conducted at the Department of Animal Science, USP / ESALQ from January 2008 to March 2009. Treatments corresponded to combinations between two pre-grazing (canopy light interception (LI) of 95 and 100% during regrowth) and two postgrazing conditions (grazing residue height of 15 and 20 cm) and were allocated to experimental units (1200m2 paddocks) according to a 2x2 factorial arrangement and a complete randomized block design, with four replications. 1 Barbero, L.M. Respostas morfogênicas de pasto de capim-mulato submetidos a estratégias de pastejo rotativo por bovinos de corte. Tese de doutorado em fase final de preparação. 6 Tiller population density (TPD) and tiller demography were evaluated. Based on the results, tiller appearance (TAR) and death rates (TDR) were calculated. To calculate tiller population stability index (SI), the following equation P1/P0= TSR (1 + TAR) was used in which P1/P0 corresponds to the current population (P1) expressed as a proportion of tiller initial population during a given period (P0), and TSR and TAR correspond to tiller survival and appearance rates during the same period, respectively. The balance between tiller appearance and death rates was also calculated. In summer-2008 higher TPD, TAR and TDR, and lower TSR were showed when compared to the autumn / winter / early spring, however the balance between tiller appearance and death was positive and close to 1 SI. Autumn / winter / early spring showed lower TPD, TAR, TDR, and higher TSR, negative balance between tiller appearance and death and SI around 1 when compared to other seasons. In late spring there was a high TPD, therefore a high TAR, TDR, lower TSR positive balance between tiller appearance and death and SI greater than 1 when compared to the autumn / winter / early spring. This time of year it is also observed that swards grazed at 95% LI had higher SI than at 100% LI. In summer 2009, there was an increase in TPD in relation to the late spring, due to high TAR, TDR and lower TSR. In almost all seasons the treatments of 95% LI showed higher TPD in relation to treatment of 100% LI. Only in summer-2008 there was no difference between grazing frequencies. Regarding grazing frequencies, in summer-2009 swards managed at 95% LI showed the lowest TSR and SI values when compared to those managed at 100% LI. There were no differences between post-grazing heights of 15 and 20 cm in relation to TAR, TDR, TSR, and SI balance between tiller appearance and death throughout the seasons. Only during the autumn / winter / early spring and summer-2009 differences were found between postgrazing heights in TPD for treatment 100/20 compared to 100/15. Mulato grass showed changes in tiller population density, tiller pattern and sward stability concerning seasons and management used, with swards grazed at 95% LI (associated to animal entrance height of 30 cm) and residue height of 15 and 20 cm resulted in better conditions for regrowth, therefore, higher population density and high rates of tiller appearance and death, featuring a pattern of intensive tiller renewal. The transition period between autumn / winter / early spring and late spring is critical to mulato grass, because it is in this time that occurs the biggest tiller renewal, defining the plant population in the sward to ensure forage production and tiller persistence during the subsequent summer.