Biotemas (Sep 2008)
Regrowth morphophysiology of Baccharis trimera (Less) DC., Asteraceae): Subsidies for control in natural pastures.
Abstract
This experiment was carried out on native grassland in Rio Grande do Sul. The purpose was to compare the vigor of the regrowth of Baccharis trimera after cutting at different heights (7 and 15cm) and phenological stages (V= vegetative; beginning of spring; FE= end of flowering; end of summer). The design was ompletely randomized with ten replications, composed by plants. The cuts were on 09/26/02 (V) and 03/14/03 (FE); the regrowth evaluation was made after the plants had achieved thermal sums of 1,525 degree-days (12/12/02) and 1,749 degree-days (06/26/03) for V-stage and FE-stage cuts respectively, by harvesting the plant shoots. The lowest regrowth was observed in the plants cut in the V-stage (22.9g DM/plant), in which the cutting height had no effect. In the FE-stage there was a significant effect of the cutting height: 21.7g DM/plant was obtained under 7cm and 75.6g DM/plant was obtained under 15cm. It was concluded that it is better to cut B. trimera in the vegetative stage (beginning of spring) at a height of 15cm to minimize possible damage to valuable forage plants. Mowing realized at the end of the summer, when the plants are in the flowering stage, needs to be severe (7cm) in order to reduce the basal stem growth. The horizontal underground system of B. trimera is formed by budding roots, and new shoots can be produced from the activation of their dormant buds.
