The study was conducted in a representative native pasture area in the transition between the Serra do Sudeste and Depressão Central of RS. The main undesirable species were represented by: carqueja (Baccharis trimera (Less.) DC.), caraguatá (Eryngium horridum (Spreng.) Less.) and alecrim (Vernonia nudiflora Less). It was evaluated the initial effect (until 60 days after application) of two methods of controlling undesirable plants on forage production, vegetation dynamics, and control efficiency: T1 - without control (control, SC), T2 - mechanical control (mechanic control, CM) and T3 - chemical control (commercial herbicide composed by Picloram (64 g/L) + 2.4-D (240 g/L), in the dosage of 5 L commercial product/ha, CQ). The treatments were organized in a complete block design, with four replications. There were no differences among treatments for the green dry matter of grasses and total DM. The forage legume biomass differed among treatments, with values of 587.9, 472.0 and 0 kg/ha of DM in the CM, CQ and SQ, respectively. The control efficiency of undesirable species in this study was 76.2% for CQ and 27.9% for CM when compared to SC. The species control efficiency, in terms of frequency of pasture components, showed that the CM treatment was not efficient at 60 days after treatment application in the control of Vernonia nudiflora (Alecrim) in the second touch (-27.7%) and Eryngium horridum (Caraguatá) in the first touch (-30.0%).
control efficiency; mowing; native grassland; weed control
