Effect of Temperature on the Dissipation of Seven Herbicides in a Biobed Matrix

Abstract

Cold winters and short, warm summers in the Canadian prairies pose a challenge for the effectiveness of onfarm biobeds for degrading agricultural pesticides. A thermo-gradient plate was used to evaluate the effect of temperature on the dissipation kinetics of seven commonly used herbicides applied to a biobed matrix composed of materials typically available on a farm. The dissipation of all seven herbicides increased with increasing incubation temperature and duration. 2,4-D, bromoxynil, and thifensulfuron-methyl dissipated completely during the 35 d incubation at 13 and (or) 20°C. Tribenuron-methyl, pyrasulfotole, thiencarbazone-methyl, and metsulfuron-methyl dissipated 93%, 70%, 64%, and 34%, respectively, at 20°C. The order of decreasing dissipation in the biobed matrix reflected the relative soil half-lives and soil sorption coefficients of the herbicides. Metsulfuron-methyl and thiencarbazone-methyl had the lowest activation energies and temperature quotients and were the least sensitive to increases in incubation temperature. At 20°C, the half-lives of all herbicides were <70 d. However, 10 yr average soil temperatures to 1 m depth from a site in Saskatoon, SK, were considerably <20°C for much of the growing season. Assuming soil temperatures to be a proxy for expected temperatures of on-farm biobeds, biobed temperatures would not be high enough for a long enough period of time to achieve complete dissipation of some herbicides. Consequently, biobeds in the Canadian prairie provinces may require supplemental heating, especially in spring and late fall, to maintain incubation temperatures of approximately 20°C to optimize the degradation of herbicides used in prairie crop production.

Simulated rainfall following the preplant application of 2,4-D and dicamba in soybean

“…The polynomial model indicated a lower accumulation of dry matter with 54 mm of rainfall, similarly to the untreated control ( Figure 2C). It is important to note that the irrigation conditions after the soybean planting presumably favored a maximum herbicide dissipation, since 2,4-D is easily degraded via hydrolysis and oxidation in wet conditions (Cessna et al 2017).…”

“…The soil residue of dicamba has more severe detrimental effects on soybean than 2,4-D, what may be related to the slow dissipation of dicamba in the environment (Kah et al 2007), whereas the 2,4-D dissipation occurs easily via hydrolysis and oxidation in wet conditions (Cessna et al 2017). Similar observations have been made for soybean, cotton and sesame (Prostko et al 2003, Thompson et al 2007, Sperry et al 2017.…”

Herbicide Residues in Agroecosystems: Fate, Detection, and Effect on Non-Target Plants

“…Generally, increasing soil temperature is also associated with the increased biological activity of the soil and degradation. Cessna et al [31] showed that degradation of metsulfuron-methyl and thiencarbazonemethyl in cold seasons was lower than in warm seasons with higher temperatures.…”

Fall-applied residual herbicides improve broadleaf weed management in ultra-early wheat (Triticum aestivum L.) production systems on the northern Great Plains

“…Weed control with fall applications can be more consistent than with spring applications, which are dependent on precipitation after application. Fall applications of these herbicides on the northern Great Plains made after soil temperatures, and subsequently microbial activity, have decreased, do not result in significant degradation of active ingredient in the soil prior to weed emergence the following spring (Cessna et al 2017, Anonymous 2020).…”