Sward structural characteristics and herbage accumulation of Panicum maximum cv. Mombaça subjected to rotational stocking managements

Abstract

Grazing strategies promote changes in sward structure that can affect patterns of herbage accumulation and sward flexibility to management. This experiment evaluated sward structural characteristics and herbage accumulation of Mombaça guinea grass (Panicum maximum Jacq. cv. Mombaça) subjected to rotational stocking managements. Treatments involved grazing when swards reached either 95 or 100% interception of the incident light (LI), to post-grazing heights of 30 and 50 cm, and were allocated to 2,000 m 2 paddocks according to a randomised complete block design in a 2 × 2 factorial arrangement with four replications, from January 2001 to February 2002. Sward canopy changed from a vertical to a more horizontal orientation as the light interception area index and height increased from post to pre-grazing. Leaf canopy height pre-grazing was stable throughout the year and around 90 and 115 cm for the 95% and 100% LI treatments respectively, indicating a potential for development and use of target-based grazing management practices. Herbage mass pre and postgrazing was lower for the 95% than the 100% LI treatments, but with higher proportion of leaf and lower proportions of stem and dead material. Treatment effects on herbage accumulation were cumulative and became more evident as the experiment progressed, with up to 6 t ha -1 DM advantage to the 95/30 treatment. Although based on a single year experiment, grazing management should aim for low herbage mass during the transition period from winter to spring in order to allow fast recovery of swards and favour herbage accumulation during the following growing season. Key words: grazing management, leaf canopy height, leaf area index, light interception CARACTERÍSTICAS ESTRUTURAIS E ACÚMULO DE FORRAGEM EM PASTOS DE Panicum maximum cv. MOMBAÇA SUBMETIDOS A ESTRATÉGIAS DE PASTEJO ROTATIVORESUMO: Estratégias de pastejo promovem alterações na estrutura do dossel, afetando os padrões de acúmulo de forragem e flexibilidade ao manejo. O objetivo deste experimento foi avaliar as características estruturais do dossel e o acúmulo de forragem em pastos de capim-mombaça (Panicum maxium Jacq. cv. Mombaça) submetidos a estratégias de pastejo rotativo. Os tratamentos corresponderam a pastejos realizados quando os pastos atingiam 95 ou 100% de interceptação da luz incidente (IL) até alturas de resíduo de 30 e 50 cm, e foram alocados às unidades experimentais (piquetes de 2000 m 2 ) segundo um delineamento de blocos completos casualizados e arranjo fatorial 2 × 2, com quatro repetições, de janeiro de 2001 a fevereiro de 2002. O dossel passou de vertical para uma orientação mais horizontal à medida que o índice de área da folhagem e altura dos pastos aumentou durante a rebrota. A altura pré-pastejo do dossel mostrou-se estável durante o experimento e em torno de 90 e 115 cm para os tratamentos de 95 e 100% de IL, respectivamente, indicando potencial para o desenvolvimento e uso de práticas de manejo baseadas em metas de condição de pasto. A massa de forragem pré e pós-pastejo f...

Forage yield and nutritive value of Panicum maximum genotypes in the Brazilian savannah

“…Hybrids PM46 and PM47 did not repeat the same score in Year 2, but they presented similar DMY in both years. They yielded close to 17 t ha -1 per year, comparable to the highest yielding Guinea grass cultivars as reported in the literature (Muir and Jank, 2004;Da Silva et al, 2009). Mombaça pastures in a rotational stocking and fertilized system (195 kg ha -1 of N) produced 20 and 26 t ha -1 in a 411-day period, managed with 30 and 50 cm of post-graze sward height, respectively (Carnevalli et al, 2006).…”

“…Mombaça is usually recognized as more productive than Tanzania (20.5 vs. 14.4 t ha -1 per year; Cecato et al, 2000). Both need intensive grazing management, due to excessive growth of stems when there is no control of sward height (Da Silva et al, 2009).…”

“…Forage production of the highest yielding Guinea grasses fertilized with 150 to 200 kg ha -1 of nitrogen is approximately 18 to 21 t ha -1 per year (Da Silva et al, 2009;Muir and Jank, 2004). Frequently, inadequate grazing management of these species results in excessive stem growth that decreases intake rate and cattle performance (Benvenutti et al, 2008).…”

“…Hybridization efforts are possible for Guinea grass due to the existence of sexual and apomictic plants (Resende et al, 2004). Although polyploid species could display a great amount of meiotic abnormalities that affect pollen viability (Singh, 1993), recent analysis has demonstrated that certain intraspecifi c Panicum hybrids present a low level amount of meiotic abnormalities and high pollen viability can be expected (Pessim et al, 2010).Forage production of the highest yielding Guinea grasses fertilized with 150 to 200 kg ha -1 of nitrogen is approximately 18 to 21 t ha -1 per year (Da Silva et al, 2009;Muir and Jank, 2004). Frequently, inadequate grazing management of these species results in excessive stem growth that decreases intake rate and cattle performance (Benvenutti et al, 2008).…”

Fontes e doses de nitrogênio e alterações nos atributos químicos de um latossolo cultivado com capim-mombaça

“…A coleta da forrageira para cada corte foi realizada com auxílio de um quadrado de ferro de 0,50 × 0,50 m (0,25 m 2 ) e cortada com tesoura de aço a 30 cm da superfície do solo, simulando a altura ideal de rebaixamento dessa forrageira (Silva et al, 2009). Após cada corte de avaliação, foi realizado o corte de uniformização de toda a área experimental, na mesma altura de corte das plantas avaliadas, sendo retirado da área o material vegetal resultante da uniformização.…”