Crescimento inicial do melão após aplicação de herbicidas em pós-emergência

The control of weeds in melon crops is hampered by the lack of selective herbicide information for the crop. The objective of this work was to evaluate the effect of post-emergence herbicide application on yellow melon and toad skin culture. Two experiments (one for each cultivar) were carried out in a completely randomized design with four replications. The treatments were composed by the application of the herbicides in post-emergence: fomesafen (250 g a.i. ha-1); flumioxazin (2000 g a.i. ha-1); fenoxaprop (110 g a.i. ha-1); ioxynil (1005 g a.i. ha-1); carfentrazone (20 g a.i. ha-1); oxyfluorfen (960 g a.i. ha-1); oxadiazon (1200 g a.i. ha-1); and control without application. Phytotoxicity evaluations were performed at 7, 14, 21 and 28 days after application (DAA). The leaf number, stem length, leaf area, stem diameter and total dry matter evaluations were performed at 28 DAA. Oxadiazon and oxyfluorfen herbicides negatively influenced the initial growth of yellow melon. Oxadiazon and ioxynil herbicides negatively influenced the initial growth of toad skin melon. The herbicides flumioxazin and fomesafen did not alter the initial growth of yellow melon and frog skin melon presenting great potential for selectivity tests.O controle de plantas daninhas em cultivos do meloeiro é dificultado pela falta de informações de herbicidas seletivos para a cultura. O objetivo deste trabalho foi avaliar o efeito da aplicação de herbicidas em pós-emergência no melão cultivar amarelo e cultivar pele de sapo. Dois experimentos (um para cada cultivar) foram realizados em casa de vegetação no delineamento inteiramente casualizado, com quatro repetições. Os tratamentos foram compostos pela aplicação dos herbicidas em pós-emergência: fomesafen (250 g i.a. ha-1); flumioxazin (2000 g i.a. ha-1); fenoxaprop (110 g i.a. ha-1); ioxynil (1005 g i.a. ha-1); carfentrazone (20 g i.a. ha-1); oxyfluorfen (960 g i.a. ha-1); oxadiazon (1200 g i.a. ha-1); mais uma testemunha sem aplicação. Avaliações de fitotoxidade foram realizadas aos 7, 14, 21 e 28 dias após a aplicação (DAA). As avaliações de número de folhas, comprimento da haste, área foliar, diâmetro do caule e matéria seca total foram realizadas aos 28 DAA. Os herbicidas oxadiazon e oxyfluorfen influenciaram negativamente no crescimento inicial do melão amarelo. Os herbicidas oxadiazon e ioxynil influenciaram negativamente no crescimento inicial do melão pele de sapo. Os herbicidas flumioxazin e fomesafen não alteraram o crescimento inicial do melão amarelo e do melão pele de sapo apresentando grande potencial para testes de seletividade

Sorption and desorption of ametryn in different types of soils

Knowledge of factors related to the dynamics of herbicides in the environment is of fundamental importance to predicting the behavior of herbicides in soils with different attributes, to select appropriate dosages, as well as to avoid harmful effects on the environment and subsequent crops. The objective of this work was to evaluate the sorption and desorption of ametryn in seven soils with different attributes. Initially, the equilibrium time was determined by the "Batch Equilibrium". Then, it was performed the sorption test with different concentrations (0.5; 1; 2; 4; 8; 16; 24 and 32 mg L-1) of ametryn in 0.01 mol L-1 CaCl2. 10 mL of these solutions were added to samples of 2.00 g of each soil, remaining under rotary shaking for 4 hours. After centrifugation and filtration, the ametryn concentration in the supernatant was determined by high-performance liquid chromatography. Desorption was evaluated using the tubes containing 16 mg L-1 prior to sorption testing. The results indicated that the sorption and desorption of ametryn depend on the physicochemical attributes of the soil. Sorption was higher in soils with high organic matter content and high ion exchange capacity, while desorption was inversely proportional to sorption

Questão agrária e políticas públicas em Minas Gerais : conflitos sociais e alternativas populares

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Controle de plantas daninhas no melão com herbicidas de pré-emergência

The objective of this work was to evaluate the effectiveness and selectivity of herbicides applied at preemergence to the melon (Cucumis melo) crop. The experiments were carried out from 2017 to 2018, in a randomized complete block design, with four replicates, in the state of Rio Grande do Norte, Brazil. The treatments consisted of the preemergence application of: 35 g ha-1 a.i. flumioxazin, 25 g ha-1 a.i. flumioxazin, 250 g ha-1 a.i. sulfentrazone, 480 g ha-1 a.i. metribuzin, 240 g ha-1 a.i. oxyfluorfen, 240 g ha-1 a.i. oxyfluorfen + 960 g ha-1 a.i. S-metolachlor, 360 g ha-1 a.i. clomazone, and 360 g ha-1 a.i. clomazone + 240 g ha-1 a.i. oxyfluorfen; in 2018, metribuzin did not show selectivity and was substituted by 480 g ha-1 a.i. ametryn and 1,600 g ha-1 a.i. diuron. Fruit yield and quality, as well as weed control and dry mass, were evaluated. The metribuzin, ametryn, and diuron herbicides caused melon plant death. The best efficiency in weed control was obtained with the mixture clomazone + oxyfluorfen, followed by oxyfluorfen, oxyfluorfen + S-metolachlor, and clomazone. The treatments with oxyfluorfen, oxyfluorfen + S-metolachlor, and clomazone + oxyfluorfen were not considered selective. Clomazone was the only selective herbicide in the two years of evaluation and can be an alternative for weed control in melon crops.O objetivo deste trabalho foi avaliar a eficácia e a seletividade de herbicidas aplicados em pré-emergência no cultivo de melão (Cucumis melo). Os experimentos foram conduzidos de 2017 a 2018, no delineamento de blocos ao acaso, com quatro repetições, no estado do Rio Grande do Norte, Brasil. Os tratamentos consistiram na aplicação pré-emergencial de: 35 g ha-1 i.a. de flumioxazin, 25 g ha-1 i.a. de flumioxazin, 250 g ha-1 i.a. de sulfentrazone, 480 g ha-1 i.a. de metribuzin, 240 g ha-1 i.a. de oxyfluorfen, 240 g ha-1 i.a. de oxyfluorfen + 960 g ha-1 i.a. de S-metolachlor, 360 g ha-1 i.a. de clomazone e 360 g ha-1 i.a. de clomazone + 240 g ha-1 i.a. de oxyfluorfen; em 2018, o metribuzin não apresentou seletividade e foi substituído por 480 g ha-1 i.a. de ametrina and 1.600 g ha-1 i.a. de diuron. Foram avaliados a produtividade e a qualidade dos frutos, bem como o nível de controle e a massa seca das plantas daninhas. Os herbicidas metribuzin, ametrina e diuron causaram a morte das plantas de melão. A melhor eficiência no controle das plantas daninhas foi obtida com a mistura e clomazone + oxyfluorfen, seguida de oxyfluorfen, oxyfluorfen + S-metolachlor e clomazone. Os tratamentos com oxyfluorfen, oxyfluorfen + S-metolachlor e clomazone + oxyfluorfen não foram considerados seletivos. O clomazone foi o único herbicida seletivo nos dois anos de avaliação e pode ser alternativa para o controle de plantas daninhas na cultura do melão

Adsorption mechanisms of atrazine isolated and mixed with glyphosate formulations in soil.

In Brazil, the atrazine has been applied frequently to join with glyphosate to control resistant biotypes and weed tolerant species to glyphosate. However, there are no studies about atrazine's behavior in soil when applied in admixture with glyphosate. Knowledge of atrazine's sorption and desorption mixed with glyphosate is necessary because the lower sorption and higher desorption may increase the leaching and runoff of pesticides, reaching groundwaters and rivers. Thereby, the objective of this study was to evaluate the adsorption mechanisms of atrazine when isolated and mixed with glyphosate formulations in a Red-Yellow Latosol. The maximum adsorbed amount of atrazine in equilibrium (qe) was not altered due to glyphosate formulations. The time to reach equilibrium was shortest when atrazine was mixed with the Roundup Ready® (te = 4.3 hours) due to the higher adsorption velocity (k2 = 2.3 mg min-1) in the soil. The highest sorption of atrazine occurred when mixed with the Roundup WG®, with the Freundlich sorption coefficient (Kf) equal to 2.51 and 2.43 for both formulation concentrations. However, other glyphosate formulations did not affect the sorption of atrazine. The desorption of atrazine was high for all treatments, with values close to 80% of the initial adsorbed amount, without differences among isolated and mixed treatments. The change in the velocity and capacity of sorption for the atrazine mixed with some glyphosate formulations indicates that further studies should be conducted to identify the mechanisms involved in this process