Pyroxasulfone is a new herbicidal molecule with residual activity to be used in Brazilian agricultural areas, it is necessary to gather information about its behavior in the soil, as well as its persistence in the environment and the risk of environmental contamination. The objective of this work was to evaluate the sensitivity of species to pyroxasulfone in order to select potential plants to be used as bioindicators in herbicide soil activity experiments. Greenhouse experiments were conducted with four species as potential bioindicators including lettuce (Lactuca sativa), cucumber (Cucumis sativus), sorghum (Sorghum bicolor), and tomato (Solanum lycopersicum). The preemergence pyroxasulfone treatments at 0, 3.125, 6.25, 12.5, 25, 50, and 100 g a.i. ha -1 . The percentage of injury of the treated species was evaluated by a visual scale of 0-100% at 7 and 14 days after treatment (DAT). We also evaluated the effect of the herbicide on plant height, root length, shoot fresh biomass, root fresh biomass, and total fresh biomass. Using the non-linear regression models was possible to estimate the dose of pyroxasulfone required to obtain 50% of the response for the analyzed variable (I 50 ). I 50 values were used to determine the susceptibility of the species evaluated. The pyroxasulfone dose-response experiments revealed three species with potential for bioassay studies. Overall, Lettuce was the most sensitive to herbicide. Sorghum may be useful species to detect pyroxasulfone soil activity based on plant height measurements (I 50 = 9.7 g a.i. ha -1 ). Cucumber also showed to be a potential candidate as bioindicators. Tomato was considered tolerant of pyroxasulfone doses evaluated.

Knowledge on weed biology and ecology is fundamental to provide suitable control practices in weed management systems. The objective of this research was to understand the effect of light and temperature on germination of Chamaesyce hirta, as well as to evaluate the effect of depth of seed placement in the soil in the emergence of the plant. Two experiments were conducted. In the first one, in the laboratory, the seeds were placed to germinate in plastic boxes and kept in a B.O.D. germination chamber, under constant temperatures of 20, 25, 30 and 35 ºC, either in the dark or under continuous light. Daily germination assessments were performed. The percentage of germinated seeds in the 10-day period and the germination speed index (GSI) were calculated. In the second trial, carried out in greenhouse conditions, 100 seeds were planted, under six levels of seeding depth (0, 1, 2, 3, 4 and 5 cm) and three soil cover conditions: no straw, under black oats (Avena strigosa) straw and under corn (Zea mays) straw. Daily plant emergence was counted along 30 days and total emergence and GSI were calculated. Germination of C. hirta seeds occurs both in the presence and absence of light. For the highest temperature, both increased germination and GSI were reported in the presence of light. The highest levels of emergence were obtained with the absence of plant cover and under corn straw at 0 cm depth. The presence of black oat straw on the soil reduced the emergence of C. hirta.

As integrações de métodos de controle, visando o manejo de buva (Conyza spp.) passaram a ser práticas fundamentais nos sistemas integrados de produção, tais como milho (Zea mays) em consórcio com capim-ruziziensis (Urochloa ruziziensis). Os objetivos deste trabalho foram avaliar a eficácia da cobertura do capim-ruziziensis sobre a supressão da buva e avaliar opções de controle químico de buva em capim-ruziziensis. O primeiro experimento foi realizado após a colheita de milho consorciado com capim-ruziziensis, realizando avaliações da infestação de buva e sua correlação com a massa seca do capim. O segundo experimento consistiu na aplicação em mistura dos seguintes tratamentos, em esquema fatorial 3 x 7: 2,4-D (1209 g ha-1 e.a.), [halauxifen-methyl + 2,4-D] (5,76 + 780 g ha-1 i.a.) e dicamba (960 g ha-1 i.a.) compondo o primeiro fator; e metsulfuron-methyl (2,4 g ha-1 i.a.), chlorimuron-ehtyl (20 g ha-1 i.a.), diclosulam (25,2 g ha-1 i.a.), saflufenacil (35 g ha-1 i.a.), bentazon (576 g ha-1 i.a.), atrazine (1000 g ha-1 i.a.) e testemunha sem aplicação de herbicidas compondo o segundo fator. O cultivo do milho safrinha consorciado com capim-ruziziensis, reduziu respectivamente, em 80, 60 e 96% a emergência, o crescimento e a massa seca das plantas de buva durante o período de entressafra. Todos os tratamentos proporcionaram controle de buva com até 8 cm, exceto 2,4-D isolado. Para plantas de 8 a 16 cm, todos os tratamentos com associação de herbicidas foram satisfatórios. Em plantas maiores que 16 cm, houve morte total das plantas com a aplicação de saflufenacil em associação com todos os herbicidas auxínicos. Os tratamentos seletivos para o capim-ruziziensis foram 2,4-D e dicamba isolados e as associações com bentazon.

O sistema de rotação de culturas tem trazidos vários benefícios tanto para o produtor quanto para o solo. Entretanto o sistema de rotação de cultura da canola com a soja pode causar danos na germinação e no desenvolvimento de plantas de soja, devido à liberação de compostos alelopáticos liberados pela palhada da canola. Diante disso, esse trabalho tem como objetivo realizar uma revisão bibliográfica apresentado alguns resultados encontrados na literatura para diminuir os efeitos negativos causados pela alelopatia da cultura da canola sobre a cultura da soja. Essas informações serão de suma importância para os produtores, auxiliando na redução do efeito alelopático e na diversificação de renda do produtor. O trabalho teve como conclusão de que a mistura de inoculantes Bradyrhizobium japonicum associado ao cobalto e molibdênio tem maior capacidade de reduzir os efeitos alelopáticos. Além disso, algumas cultivares de soja são mais suscetíveis a esses compostos comparadas a outras.

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.