Leaching and residual activity of imidazolinone herbicides in lowland soils

Abstract

Herbicides used in the Clearfield® rice (Oryza sativa L.) production system have a potential for leaching. This can result in contamination of underground water resources and cause injury to not tolerant crops that are sown in a succession and/or crop rotation. The objective of this study was to determine the leaching potential and the residual activity of the herbicides used in the Clearfield® rice system. The experiment was conducted over a period of two years and consisted of conducting a field test to be followed by two bioassays with a year of difference between their implementation. Initially an experiment was conducted in lowland area where it was planted the cultivar of rice ‘PUITA INTA CL’. Approximately one and two years thereafter, soil samples from each plot were collected at intervals of 5cm to a depth of 30cm (B factor) for the bioassay to evaluate persistence of herbicides. Factor A was composed of mixtures formulated of imazethapyr + imazapic (75 + 25g a.i. L-1), imazapyr + imazapic (525 + 175g a.i. kg-1) in two doses, imazethapyr (100g a.i. L-1) and treatment control without application. Basing on results, it was concluded that the mixtures imazethapyr + imazapic, imazapyr + imazapic and imazethapyr leached into the soil, reaching depths of up to 25cm in lowland soil. Imidazolinone herbicides used today in the irrigated rice Clearfield® system are persistent in soil, and their phytotoxic activity can be observed up to two years after application.

Assessment of Glyphosate Impact on the Agrofood Ecosystem

“…Glyphosate residues are linked to its applications calendar and soil inputs; thus, the need to reduce overspray, but also to focus on its relative mobility/persistence [ 143 ]. Residual levels in sediments and water streams may be diluted with the upper part of the basin devoted to woodland, because it is not used in woodlands, and woodlands themselves help to reduce and prevent diffuse pollution [ 144 ].…”

Introduction of imidazolinone herbicide and Clearfield® rice between weedy rice—control efficiency and environmental concerns

“…Concern should also be given to the interaction and destination of these dangerous chemical particles, which may be adsorbed in different forms, such as minerals and organic compounds, and to their reaction with other compounds, forming complexes. Refatti et al (2017) reported that the extensive use of herbicides close to water sources is considered a risk of contamination to the environment. There is no doubt that the fate of herbicides in the crop fields causes pollution both on the surface and in groundwater, as it is also harmful to human health by affecting the food chain; studies revealed that less than 1% of herbicide components can reach the target in plants, and the rest of the herbicide penetrates and moves through soil pores in surface and groundwater (Gavrilescu 2005).…”

“…Leaching (the vertical movement of herbicide components along the soil matrix) and degradation are both key factors determining the mobility of herbicides downstream. The persistence and leaching of the of IMI herbicides in the soil are due to many factors such as photodegradation, chemical degradation, microbial activity, and the hydrolysis process (Refatti et al 2017). The two mechanisms (microbial and chemical) are correlated with water availability and high temperature (Süzer and Büyük 2010).The photodegradation process has been considered one of the main processes, especially in tropical and subtropical areas, due to the hot temperatures and high solar radiation all day long (Ramezani et al 2009).…”

“…Sondhia et al (2015) reported that IMI-herbicides persisted for a longer period in Romanian soil and demonstrated residual effects on the next crop rotation after two to three years. (Table 7) summarizes the studies exploring the different depths which IMI-herbicides could leach into; here, it is revealed that the translocation and leaching of IMIherbicide components between soil particles and the continuation of IMI-herbicides at diverse depths in the soil may increase their persistence, possibly due to the lower temperature at greater depths, less solar radiation, and the decreased activity of microorganisms in the soil (Refatti et al 2017). Battaglin et al (2000) showed that approximately 2.5% of the applied pesticide was wasted in runoff during rainfall from one to two days after the application of herbicides.…”

“…Recently, Refatti et al (2017) reported that the IMI-herbicides used in the Clearfeld ® rice system could leach up to 25 cm or more. Similarly, IMI-herbicides were found to exceed the method reporting limit (MRL) of 0.01 µg/l in 83% of total water samples in US (Battaglin et al 2000).…”