O manejo de desfolhação em estações prévias e o corte de uniformização modificam o desenvolvimento do capim-marandu?

Abstract

The residual effects of the defoliation management of tropical forage grasses are cause for concern, both for farm pasture managers and for researchers in forage science. Some management techniques, such as the uniformization cut, through mowing, have been used in both cases to suppress or remove such effects. In this sense, an experiment was conducted with marandu palisadegrass (Brachiaria brizantha cv. Marandu syn. Urochloa brizantha cv. Marandu) aiming to understand the efficiency of the uniformization cut in forage canopies to remove the residual effects from previous managements in subsequent seasons, and if the cut itself promotes such effects. The treatments were defined as the following defoliation strategies: (i) canopy with 30 cm throughout the experimental period; (ii) 15 cm canopy in summer, autumn and winter; and, after the cut (C), 30 cm from spring onwards (15-C-30); and (iii) 60 cm canopy in summer, autumn and winter; and, after the cut, 30 cm from spring onwards (60-C-30). It was analyzed the leaf elongation rate (LElR), stem elongation rate (SElR) and leaf senescence rate (LSeR) of individual tillers, and the leaf growth rate (LGR), stem growth rate (SGR), leaf senescence rate (LSR) and tiller population density (TPD) of forage canopies. It was found that, compared to the canopy under 30 cm, the growth rates of individual tillers and forage canopies were higher in those submitted to the uniformization cut at the end of winter only in the first two months of evaluation. In the cut forage canopies (15-C-30 and 60-C-30), the development pattern was similar after the uniformization cut. The tillers population was lower in the 30 cm canopies in the last four months of the evaluation, because of the death of old tillers that were not cut at the end of winter, causing a decrease in the TCF in the months of March and April. Thus, it was concluded that the uniformization cut was effective in suppressing the residual effects of the managements used in the previous seasons and also caused different patterns of canopy development, compared to the canopy that was always kept at the same height throughout the experimental period.