Competition with weeds is one of the obstacles to achieve high yields in jatropha harvest. The chemical method is an alternative weed control due to its high efficiency, readiness and economy, when compared to other methods. However, products recommended for this crop are scarce. This study aimed at evaluating the effects of pre and post-emergence clomazone formulations at the initial development of jatropha. Two experiments were conducted under a randomized blocks design, in a 2 x 5 factorial arrangement, with four replications, consisting of the combination of two clomazone formulations (encapsulated suspension and emulsifiable concentrate) and five doses (0 g ha-1, 250 g ha-1, 500 g ha-1, 1,000 g ha-1 and 2,000 g ha-1). The dry matter of the plants was reduced both in the pre-emergence and post-emergence applications. Net photosynthesis was not affected by the application of clomazone in both formulations. The encapsulated suspension formulation is less phytotoxic than the emulsifiable concentrate formulation for pre and post-emergence applications. However, both formulations negatively affect the early development of jatropha plants.

Taxa de semeadura de Brachiaria brizantha consorciada com milho na incidência de plantas daninhas RESUMOA cobertura vegetal do solo promovida pela Brachiaria brizantha pode reduzir a incidência de plantas daninhas na área de cultivo. Assim, o presente trabalho objetivou estudar o efeito do consórcio de milho com B. brizantha em diferentes taxas de semeadura sobre a incidência de plantas daninhas. O experimento foi conduzido a campo em solo classificado como Latossolo Vermelho eutroférrico. O delineamento experimental utilizado foi de blocos ao acaso em esquema fatorial 4 x 2, sendo uma testemunha com milho solteiro, três densidades de semeadura de B. brizantha (7,5, 15 e 22,5 kg ha -1 de sementes) em consórcio com a cultura do milho, e dois períodos de avaliação da incidência de plantas daninhas na área, realizados 150 e 180 dias após a colheita do milho e dessecação da B. brizantha. Foi constatada oscilação na população de plantas daninhas entre as duas épocas de avaliação, enquanto as taxas crescentes de semeadura de braquiária proporcionaram redução linear na população de plantas daninhas. Palavras-chave: Braquiária, cobertura do solo, Zea mays.Seeding rate of Brachiaria brizantha intercropped with corn in the incidence of plants ABSTRACT Soil vegetation cover promoted by Brachiaria brizantha can reduce the incidence of weeds in the cropping area. Thus, the objective of the present study was to evaluate the effects of corn intercrop with Brachiaria brizantha in different sowing rates on the incidence of weeds. The experiment was carried out in a field experiment in a soil classified as an Oxisol. The experimental design was made in randomized blocks, with a factorial scheme 4 x 2, with one sole cropped corn as control, three B. brizantha (7.5, 15 and 22.5 kg ha -1 ) sowing rates, intercropped with corn crop, and two evaluation periods of weed incidence in the area, made at 150 and 180 days after the corn harvest and B. brizantha desiccation. The weed population varied in the two evaluation periods, while the increasing sowing rates of B. brizantha provided linear reduction in the weed population.