Control of Brachiaria decumbens and Panicum maximum by S-metolachlor as influenced by the occurrence of rain and amount of sugarcane straw on the soil

Abstract

ABSTRACT.With the objective to study the control of Brachiaria decumbens and Panicum maximum by herbicide S-metolachlor as influenced by the time interval between the herbicide application the occurrence of rain and the amount of sugarcane straw on the soil, two experiments were conducted in pots under greenhouse conditions. In the first, the factors were the amount of sugarcane straw left on the soil surface (0, 3, 6, 10, or 15 ton. ha -1 ) and the S-metolachlor applied at doses of 0, 0.96, 1.44, 1.92, or 2.40 kg ha -1 . In the second, the factors were the amount of sugarcane straw left on the soil surface (0 or 10 ton. ha -1 ), the interval of time elapsed between the application of S-metolachlor and simulated rain, which took place 1 day before and 0, 4, 8, 12, 16, or 20 days after the application. The herbicide doses were not affected by the amounts of straw left on the soil surface. When straw was not left on the soil surface, the control of the weeds by the herbicide was not influenced by the time interval up to 20 days after herbicide application. With 10 ton. ha -1 of straw, the control exerted by S-metolachlor was equally efficient whether it rained up to 12 days after the herbicide application. P. maximum was controlled even when the rain fell one day before the herbicide application.Keywords: signal grass, buffalo grass, crop residues, herbicide leaching. Controle deBrachiaria decumbens e Panicum maximum pelo herbicida S-metolachlor em função da ocorrência de chuva e da quantidade de palha sobre o solo RESUMO. Com o objetivo de estudar o controle em pré-emergência de Brachiaria decumbens e Panicum maximum pelo herbicida S-metolachlor em função do intervalo de tempo entre a aplicação e a ocorrência de chuva e da quantidade de palha de cana-de-açúcar na superfície do solo, dois experimentos foram desenvolvidos em vasos mantidos em casa de vegetação. No primeiro, foram estudadas cinco quantidades de palha sobre o solo (0, 3, 6, 10 e 15 t ha ) e sete intervalos de tempo entre a aplicação de Smetolachlor e a simulação de chuva (1 dia antes; logo após; 4, 8, 12, 16 e 20 dias após a aplicação). As dosagens de S-metolachlor não foram afetadas pelos níveis de palha na superfície do solo. Além disso, sem a manutenção de palha sobre o solo, o controle das plantas daninhas pelo herbicida S-metolachlor não foi influenciado pelos intervalos de tempo entre a aplicação e a simulação de chuva, até 20 dias. Com 10 t ha -1 de palha, o controle de B. decumbens e P. maximum pelo S-metolachlor não foi prejudicado quando choveu até 12 dias da sua aplicação ou um dia antes, mas, nesse caso apenas para P. maximum.Palavras-chave: capim-braquiária, capim-colonião, resíduos vegetais, lixiviação de herbicida.

Efficacy of S-metolachlor + glyphosate for Weed Control in Different Levels of Eucalyptus Straw

“…By reducing fatty acid levels, S-metolachlor inhibits growth and causes embryonic mortality [47,50]. In grasses, the product acts on the epicotyl, which generates reductions in the aerial part and biomass accumulation [32]. In addition, grasses subjected to the herbicide produced less biomass using the same amount of water, which suggests that water use efficiency decreased as a function of the amount of herbicide applied [51,52].…”

“…This is because herbicides, mainly pre-emergent, have to cross this barrier and reach the soil to control the seed bank [28,29]. However, straw also reduces exposure to light, the performance of photosynthesis, and the emergence of weeds [30,31], in addition to benefiting the soil with moisture, nutrients, and an environment favorable for the microbiota [32].…”

Sensitivities of Urochloa decumbens Plants to Glufosinate

“…In the literature, there are few works on the sensitivity of plants of the genus Brachiaria to herbicide application (Petter et al, 2011;Correia et al, 2012), especially to glufosinate herbicide, considering the low genetic variability of species of this genus. For this reason, studies that seek to understand the sensitivity of plant populations to herbicides, as well as their effect over time, are important for the development of weed management strategies, and also for predicting the impact of adopting such weed management practices on the infesting population.…”