Persistence of Imidazolinones in Soils Under a Clearfield System of Rice Cultivation

Abstract

-The commercial mixture of imazethapyr and imazapic herbicides has been used for the control of red rice and several other species of weeds found in rice crops; this system called Clearfield. However, its use may limit the succession of non-tolerant crops for long residual activity. The research objective with this work was to determine the persistence of imazethapyr, imazapic and their mixture in three soils in the Brazilian state of Tocantins. Three experiments were conducted in a completely randomized design with four replications, each corresponding to the evaluated soil (Haplic Plinthosol (FX), red-yellow Latosol (LVA) and Haplic Gleysol (GX)). The treatments were arranged in a split plot design, with the allocated plots herbicides (imazethapyr and imazapic alone and commercial mixture) and the plots allocated the 11 evaluation times (1, 15, 30, 45, 60, 75, 90, 105, 120, 135, 150 days after treatment (DAT)), and a control without application. Contacted up long residual effect of imazethapyr and commercial mixture of imazethapyr and imazapic, regardless of assessed soil. After 150 days of applying herbicides or the commercial mixture, their residues in the soil also inhibited approximately 94% of the mass of the dry matter accumulation of the indicator plants. When imazapic was applied alone, there was a higher dry matter accumulation of the indicator plants, indicating less residual effect of this herbicide in the soil and this was attributed to the lower dose of this herbicide applied. The attributes of the soil pH, texture and iron oxides were what most affected the persistence of the herbicides. It can be concluded that the persistence of imazethapyr and imazapic is too long in the Brazilian state of Tocantins soils and the use of these herbicides in the region should be avoided due to the high risk of the occurrence of carryover,or be well planned, as land use in rotation for susceptible crops. (1, 15, 30, 45, 60, 75, 90, 105, 120, 135 Keywords

Degradation of Imazapyr and Imazapic in Aqueous Solutions and Soil Under Direct Sunlight

“…Once the herbicides penetrated underneath the soil surface, the photodegradation activity became low [27] and this might contribute to their persistency in the environment. Since imazapyr and imazapic were able to remain longer in the soil, these herbicides also had a higher probability to leach into groundwater as reported previously [14,29]. Conclusion Photodegradation of imidazolinone herbicides could be an important factor for their breakdown in the environment as demonstrated in the tabulated results.…”

“…There are many factors affecting the persistency of herbicides molecule in the environment and these may include sorption, volatilisation, leaching and degradation (abiotic and biotic) [3,14]. Photodegradation may play an important role for the breakdown of herbicides in environment because all pesticides are susceptible to this process to a certain degree [3].…”

Estimation of sulfentrazone sorption in isolated application and mixed with glyphosate

“…From the toxicological point of view, herbicide retention reduces the available concentration in the soil solution for microbial degradation, uptake by plants, and leaching into the soil profile (SOUZA et al, 2016). The physical and chemical characteristics of the herbicide molecule and the soil define the capacity and intensity of the sorption and desorption of an herbicide to the soil, and consequently the ability of these compounds to contaminate the environment (ČADKOVÁ et al, 2013;SOUZA et al, 2016). When applied in a mixture, interactions between these molecules can occur, altering the sorption processes and consequently the behaviour of one or both molecules.…”

Espécies indicadoras de resíduos de saflufenacil em solos

“…Para se compreender a dinâmica do herbicida no ambiente são necessários diversos estudos referentes a sorção, a lixiviação e a persistência de suas moléculas nos diferentes tipos de solo. Conhecendo-se estas variáveis, é possível fazer uma estimativa do possível destino dos herbicidas no ambiente (SOUZA et al, 2016;KERMINEN et al, 2018;MENDES et al, 2018). Os estudos mencionados acima podem ser realizados por métodos biológico e químico ou pela associação dos dois métodos (ANDRADE et al, 2010;BRAGA et al, 2016;FARIA et al, 2018).…”