Activity, adsorption, mobility, and field persistence of pyrithiobac in three soils

Abstract

Petri dish bioassays, based on root response of corn grown in soil and perlite, were used to study the activity, adsorption, and leaching of pyrithiobac in a clay, loam, and a clay loam soils containing 2.3, 1.4, and 1.3% organic matter, respectively. Both bioassays indicated that activity of pyrithiobac (reduction of corn root length) increased with increasing herbicide concentration, but in a nonlinear manner, particularly at higher concentrations. Activity of pyrithiobac was similar in clay loam and loam soils, but was lower in clay soil. Adsorption distribution coefficients (K d) for the clay, loam, and clay loam soils were 0.56, 0.10, and 0.24, respectively. Pyrithiobac leached through all three soils, and biologically available herbicide was detected below 30 cm in all soils; however, the amount leached through the clay soil was lower than that leached through the other two soils. Field persistence of pyrithiobac applied preplant incorporated (PPI), preemergence (PRE), or postemergence (POST) at 68, 102, or 136 g ha−1 was similar in loam and clay loam soils, but was more persistent in clay soil. Pyrithiobac applied POST in clay and loam soils was more persistent than that applied PPI or PRE; however, in clay soil field persistence of POST pyrithiobac was similar with that applied PPI or PRE. Biologically available residues were not detected in 0- to 10-cm soil depth 120 d after any herbicide treatment applied either PPI or PRE in all soils, but this was not the case for pyrithiobac applied POST in the loam soil. Adsorption of pyrithiobac was very low in all three soils, and this was the reason for its increased mobility even below 30-cm depth in all soils. The field persistence of pyrithiobac was generally less than one growing season. However, some pyrithiobac may have moved deeper in the soil and could be harmful to rotational crops after plowing or through capillary movement upward.

Prickly Sida (Sida spinosa L.) and Cotton Response to Pre- and Early Post-Emergence Herbicides

“…This lowered the efficacy of these treatments as reflected in our results one week later (4 WAT). Our observation is in line with previous studies on the relatively high leaching potential and persistence of pyrithiobac in the soil [30,31]. Pyrithiobac is a weak acid; therefore, the slightly acidic soil (pH 5.88) of our experimental field is expected to have aggravated its leaching capacity.…”

“…The increase in efficacy using these treatments between 4 and 8 WAT in 2022 was probably due to subsequent capillary movement upward of pyrithiobac in the weeks after the heavy rainfall that year. The potential of pyrithiobac capillary upward movement is also mentioned in previous studies [30]. As the season progressed, the rise in temperature and subsequent evaporation of the surface soil water probably increased the capillary upward flow of deeper-level soil water containing pyrithiobac.…”

Seleção de espécies bioindicadoras para os herbicidas trifloxysulfuron-sodium e pyrithiobac-sodium

“…As plantas suscetíveis acabam morrendo, devido à incapacidade de produzir os aminoácidos essenciais para o seu ciclo vital (Oliveira Jr., 2001). Embora sejam predominantemente utilizados em pós-emergência, estes herbicidas também possuem atividade no solo (Veletza et al, 2005;Minton et al, 2008). Este fato pode acrescentar atividade residual à ação pós-emergente destes herbicidas, mas, por outro lado, pode também representar risco potencial para espécies cultivadas em sucessão.…”

“…Esse fato pode limitar sua utilização em áreas onde o agricultor cultiva, por exemplo, feijão no inverno (Procópio et al, 2004), milho e sorgo (Minton et al, 2008). O pyrithiobacsodium apresenta atividade biológica superior a 120 dias, o que também pode causar injúrias em culturas de sucessão como sorgo, milho, trigo e arroz (Veletza et al, 2005). No Brasil, estudos sobre o comportamento destes herbicidas no solo são escassos.…”

Persistência de trifloxysulfuron-sodium e pyrithiobac-sodium em diferentes tipos de solo

“…% inibição da matéria fresca % inibição da matéria fresca dose utilizada), ainda foi possível detectar sua atividade no solo. No entanto, em campo, a persistência desse herbicida não é observada por períodos tão longos, o que pode ser resultado da sua mobilidade no perfil do solo (Matocha & Hossner, 1998Veletza et al, 2005).…”