The grazing behavior practice by bovines can be positive or negatively influenced by the pasture structure where the animal is inserted. Several factors determine the pasture structure and the presence of weeds is considered one of the most important. This study aimed to assess the effect of species with and without stiff structures over the grazing behavior of bovines in pasture areas. The experimental design was a split block design with four replications, in which treatments were arranged in a 4 x 3 factorial design: four weed species (Zanthoxylum rhoifolium, Cnidoscolus urens, Dasyphyllum brasiliensis, and Luehea divaricata) associated with three proximity strips of weeds: 0-50, 50-100, and 100-150 cm in relation to the main stem of the studied weed. Forage intake by animals was measured by determining the real forage offers at 0, 3, 6, 9, and 15 days after the beginning of animal grazing (DAP). The presence of noxious shrubs influenced bovine grazing behavior. The influence on the intake is most evident in the presence of plants that promote animal discomfort. The species Z. rhoifolium, C. urens, and D. brasiliensis were the weeds with the greatest influence on feed access among the species that have stiff structures. The negative influence on grazing behavior is higher in the proximity strip closest to the plant, i.e. 0-50 cm from the main stem of the weed.

Resumo -A dificuldade de controle das plantas daninhas tem sido considerada como um dos principais entraves ao sucesso dos projetos de recuperação da vegetação em áreas degradadas. O presente trabalho teve o objetivo de avaliar o efeito de diferentes herbicidas pré-emergentes sobre a emergência, sobrevivência e desenvolvimento inicial de plantas das espécies nativas amendoim bravo (Platypodium elegans), mutamba (Guazuma ulmifolia), carobinha (Jacaranda micrantha) e angico cuiabano (Anadenanthera colubrina). O experimento foi desenvolvido em casa de vegetação no delineamento experimental inteiramente casualizado, com cinco repetições. Os tratamentos foram constituídos pela aplicação em pré-emergência dos seguintes herbicidas e doses: isoxaflutole (75, 150 e 300 g i.a. ha -1 ), pendimenthalin (500, 1000 e 2000 g i.a. ha -1 ), trifluralin (600, 1200 e 2400 g i.a. ha -1 ) e uma testemunha padrão sem a aplicação de herbicidas. O efeito dos herbicidas foi avaliado quanto ao número de plântulas emergidas, número de folhas por plântula, altura de plântulas, diâmetro de plântulas na altura do coleto e matéria seca de raiz e folhas aos 35 dias após a germinação. Com os resultados obtidos foi possível afirmar que todos os herbicidas e doses utilizadas não prejudicaram a emergência e o desenvolvimento inicial das espécies P. elegans e J. micrantha. As doses de 150 e 300 g i.a. ha -1 do herbicida isoxaflutole foram não seletivas para a espécie arbórea G. ulmifolia. Apenas a dose de 600 g i.a. ha -1 do herbicida trifluralin apresentou seletividade para a espécie A. colubrina.Abstract -The weed control difficulties has been considered one of the most obstacles to success of forest recovery projects at degraded areas. This experiment aimed to evaluate the different pre-emergent herbicides effect on seed emergence, seedling survival and initial development of Brazilian native tree species Platypodium elegans, Guazuma ulmifolia, Anadenanthera colubrine and Jacaranda micrantha. The experiment was conducted under greenhouse conditions in a completely randomized design with five replications. The treatments were constituted by the pre-emergence application of the following herbicides and doses: isoxaflutole (75, 150 and 300 g a.i. ha -1 ), pendimenthalin (500, 1000 and 2000 g a.i. ha -1 ), trifluralin (600, 1200 and 2400 g a.i. ha -1 ) and untreated herbicide as a check control. The effect of the herbicides was evaluated for the number of seedlings emerged, number of leaves per seedlings, height of seedlings, diameter of stem and dry matter of root and leaves at 35 days after germination. With the results obtained it was possible to affirm that all herbicides and their respective rates were safe to P. elegans and G. ulmifolia trees. Isoxaflutol at 150 and 300 g a.i. ha -1 was not selective to G. ulmifolia specie. Only trifluralin at 600 and 1200 g a.i. ha -1 sowed selectivity to A. colubrina specie.

This research aimed to study weed interference relationship on morphogenesis, yield, and greenhouse gas production potential of Urochloa ruziziensis under pasture renovation conditions. The experimental design was a randomized block design with four replications. Treatments consisted of seven coexistence periods: 0, 15, 30, 45, 60, 75, and 90 days after emergence (DAE). The following morphological parameters were analyzed: number of tillers, number of leaves, photosynthetically active leaf blade biomass, fresh stem biomass, dead material biomass, and total dry biomass. In vitro analyses of methane (CH4) and carbon dioxide (CO2) production were also carried out. The results were submitted to analysis of variance by the F-test, and the test of means was carried out by the Scott-Knott test at 5%. Biomass, CH4, and CO2 production of U. ruziziensis were modified with only 15 days of weed coexistence, with an effect even higher from 45 DAE. Therefore, weeds interfere with all morphological parameters, yield, and greenhouse gas production in the pasture establishment with the forage grass U. ruziziensis.

The occurrence of weeds has been the main obstacle to vegetation recovery in Cerrado areas unduly occupied by agricultural and livestock activities. This study evaluates the effect of different pre-emergent herbicides on the emergence, survival, and early development of seedlings of the native species jatobá (Hymenaea stigonocarpa), urucum (Bixa orellana), dry flour (Albizia hasslerii), and white jurema (Mimosa interrupta). The experiment was carried out under greenhouse conditions in a completely randomized experimental design with five replicates, where the treatments were constituted by herbicides: isoxaflutole, applied at the doses of 100, 200, and 300 g ai ha-1 ; pendimethalin, at 500, 1000, and 4000 g ai ha-1 ; and trifluralin, at 600, 1200, and 2400 g ai ha-1 ; in addition to a control treatment, without the application of herbicides. Herbicide phytotoxicity was evaluated at 35 days after emergence for the number of emerged seedlings, number of leaves per seedling, seedling height and diameter, and root and shoot dry weight. With the results obtained, it is possible to affirm that under the conditions of the experiment, all the herbicides and doses used did not affect the emergence and early development of seedlings of species H. stigonocarpa and B. orellana. For species A. hasslerii, the dose of 300 g ai ha-1 of herbicide isoxaflutole was not selective. All doses of the herbicide trifluralin showed selectivity for species M. interrupta.