Tillering of piatã grass subject intermittent cutting

ABSTRACT The aim of this study was to evaluate the tillering of Brachiaria brizantha cv. Piatã, as a basis for identifying the frequencies and post-cutting heights most suitable for this grass. In a 2 x 2 factorial scheme, combinations between two cut frequencies (95% and maximum light interception, IL max ) and two post-cut heights (15 and 20cm) were studied. The experimental design was in randomized blocks with 3 replicates, totaling 12 experimental units of 14m 2 each. Rates of appearance (TAR) and mortality (TMR) of tillers, the stability index and the population density of tillers were evaluated. The highest TAR in the canopy under 95% IL occurred in Summer 1, in comparison to the other seasons. In the canopies managed with IL max , TAR was higher in summer 1 and in autumn, when compared to other seasons. In summer 1 and at the end of spring and summer 2, there were the highest TMR for the two cutoff frequencies evaluated. In autumn, TMR was also high in the canopy cut with IL max . IE was lower during summer 1 in the canopy under IL max and 15cm of residue (0.995). However, at other times, stability index values were greater than one unit and were not influenced by post-cut frequency and height. The population density of tillers was lower in Summer 1, when compared to the other seasons. The piata grass may be defoliated with any combination of light intercepts, 95% and ILmax, and post-cut heights, 15 or 20cm, without impairing the persistence of pasture.

摘要 本研究旨在评估毕坦臂形草（Brachiaria brizantha cv. Piatã）的分蘖特性，为确定该牧草最适宜的刈割频率及刈后留茬高度提供依据。本试验采用2×2因子设计，设置2个刈割频率（95%光截留量与最大光截留量，ILmax）以及2个刈后留茬高度（15cm与20cm）进行组合处理。试验采用随机区组设计，设置3次重复，共包含12个试验单元，每个单元面积为14m²。测定指标包括分蘖出现速率（TAR）、分蘖死亡率（TMR）、稳定性指数以及分蘖种群密度。与其他季节相比，95%光截留量处理的冠层在第1夏季的分蘖出现速率最高。在采用最大光截留量（ILmax）管理的冠层中，第1夏季与秋季的分蘖出现速率高于其余季节。在第1夏季、春季末及第2夏季，两种刈割频率处理下的分蘖死亡率均达到最高值；秋季时，采用ILmax处理的冠层分蘖死亡率同样较高。在ILmax与15cm留茬处理的冠层中，第1夏季的稳定性指数（IE）最低（0.995），其余时段的稳定性指数值均大于1，且不受刈割频率与留茬高度的影响。与其他季节相比，第1夏季的分蘖种群密度最低。毕坦臂形草可采用95%光截留量、ILmax任意刈割频率组合，搭配15cm或20cm刈后留茬高度进行刈割，不会降低草地持久性。