Resumo -O controle químico de plantas daninhas na cultura do sorgo é limitado pela baixa quantidade de herbicidas registrados para a cultura. Estudos sobre os efeitos e eficácia dos herbicidas na cultura do sorgo são fundamentais para aumento de alternativas para o controle da comunidade infestante. A partir deste contexto, o presente trabalho teve como objetivo avaliar o efeito de intoxicação provocado pelos herbicidas na cultura do sorgo, bem como a eficácia destes para o controle de plantas daninhas. O experimento foi realizado a campo no delineamento em blocos casualizados, avaliando-se oito tratamentos com quatro repetições. Os tratamentos foram constituídos por três herbicidas aplicados em pré-emergência (g ha -1 ): trifluralin (1200), Smetolachlor (768) e clomazone (1000); quatro tratamentos com herbicidas aplicados em pós-emergência: bentazon (720), bentazon + atrazine (480 + 880), atrazine (2200) e bentazon + pendimethalin (720 + 1000); além de uma testemunha sem herbicida (com plantas daninhas). Os herbicidas aplicados em pré-emergência (clomazone, trifluralin e S-metolachlor) causaram elevada intoxicação às plantas de sorgo. Não foram constatadas injúrias nas plantas de sorgo pela utilização dos herbicidas em pós-emergência. Os herbicidas clomazone e trifluralin apresentaram controle para todas as plantas daninhas monocotiledôneas avaliadas, entretanto o S-metolachlor somente não obteve controle para C. echinatus. O uso de atrazine ou a sua mistura com bentazon se mostrou promissores para controle de plantas daninhas dicotiledôneas. Palavras-chaves: controle químico; dicotiledôneas; monocotiledôneas; intoxicação Abstract -Chemical weed control in sorghum crop is limited by the low quantity of herbicides registered for the crop. Studies on the effects and effectiveness of herbicides in sorghum crop are essential to increase alternatives for the control of weeds. In this context, the present study was to evaluate the effect of intoxication caused by herbicides in sorghum, as well as the effectiveness of these for weed control. The experiment was conducted the field in a randomized block design, evaluating eight treatments with four replications. The treatments consisted of three herbicides 1 Recebido para publicação em 27/05/2016 e aceito em 24/09/2016. 2 Mestre em Produção Vegetal pela Universidade de Rio Verde, Rio Verde, GO, Brasil.
-Because of its intrinsic characteristics, sicklepod (Senna obtusifolia) has gained importance in sugarcane, especially where there is a predominance of straw after mechanical harvest. The objective of this study was to evaluate the efficacy of preemergence herbicides used in sugarcane to control sicklepod in different soil textures and application timings. Two experiments were carried out for each application season (dry and wet), and one experiment for each soil textural class (clay and sandy clay loam), totaling four experiments. The treatments consisted in 17 herbicides in the wet season and 11 herbicides in the dry season (all herbicides were applied at 50 and 100% of the recommended dose) and a check without application for each season and soil, and the design was completely randomized. Soil texture and application timing have altered the herbicide efficacy. For the wet season, initially, all herbicides, except trifluralin and smetolachlor, resulted in satisfactory control of sicklepod. Tebuthiuron was the herbicide that provided the longest period of residual control. For the dry season, amicarbazone, flumioxazin, hexazinone, imazapic, [diuron + hexazinone] F1 and isoxaflutole were efficient in both soils, but only in initial evaluations; [diuron + hexazinone] F1 and amicarbazone were the herbicides that provided the longest period of residual control. Keywords: residual control; preemergence; sicklepod; herbicides Resumo -Devido às suas características intrínsecas, o fedegoso (Senna obtusifolia) tem ganhado importância em canaviais, principalmente onde há predomínio de palhada após a colheita mecânica. O objetivo deste trabalho foi avaliar a eficácia de herbicidas pré-emergentes utilizados na cultura da cana-de-açúcar no controle de fedegoso em solos de diferentes texturas e épocas de aplicação. Foram realizados dois experimentos para cada época de aplicação (seca e úmida), sendo um para cada classe textural de solo (muito-argiloso e franco-argilo-arenoso), totalizando quatro experimentos. Os tratamentos foram constituídos por 17 herbicidas na época úmida e 11 herbicidas na época seca (todos os herbicidas foram aplicados em 50 e 100% da dose recomendada), além da testemunha sem aplicação para cada época e solo, sendo o delineamento inteiramente ao acaso. O
Sweet sorghum (Sorghum bicolor (L.) Moench) is an interesting alternativefor biomass and ethanol production, however, so far there is very limited knowledge regarding selective herbicide options for weed control in this crop. The objective of this study was to evaluate the selectivity of preemergence herbicides for sweet sorghum. This research was composed by two steps: in the first one, a greenhouse screening was carried out with several herbicide treatments and in the following step the most selective treatments were evaluated on field conditions. In sandy clay loam texture soil, the treatments involving atrazine (1000 and 2000 g ha-1), amicarbazone (210 g ha-1), trifluralin (500 g ha-1) and flumioxazin (25 g ha-1) provided the greatest levels of selectivity to sweet sorghum. In clay soil (64.7% clay), the treatments with atrazine (1000, 1500 and 2000 g ha-1), amicarbazone (280 g ha-1), S-metolachlor (480 g ha-1), [atrazine + S-metolachlor] ([601+471,2 g ha-1), pendimethalin (500 g ha-1) and imazethapyr (42.4 and 63.6 g ha-1) provided the lowest levels of crop injury, and were considered as the most selective for sweet sorghum. Herbicide treatments applied to sandy clay loam soil provided more injuries to sweet sorghum than those applied to clay soil.
The small number of herbicides registered for sorghum (Sorghum bicolor (L.) Moench) restricts its cultivation. The aim of this study was to evaluate the selectivity of herbicides applied alone or in tank mixtures to sweet sorghum in post-emergence. Two experiments were conducted in greenhouse, the first with herbicides applied alone and the second with herbicide mixtures. Based on the results of greenhouse experiments, treatments were selected to evaluate selectivity in the field. In the field experiment, the herbicides applied alone and herbicide mixtures did not differentiate from the control without herbicide application regarding to phytotoxicity, fresh mass of the aerial part, percentage of dry mass of the aerial part and Brix of sweet sorghum at 28 days after application. The treatments considered selective were: atrazine (1000 to 2000), bentazon (360 to 720), S-metolachlor (576 to 864), mesotrione (48 to 150), carfentrazone (4 to 8), 2,4-D amine (335 to 670), besides mixtures with [atrazine + S-metolachlor] [601 + 471.2] and [901.5+ 706.8], atrazine + 2,4-D amine (1000 to 2000 + 100.5 to 268), atrazine + tembotrione (1000 + 42 to 63) and atrazine + mesotrione (1000 + 48 to 72) (doses in g a.i. ha -1 ).
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