Soil Persistence of Thiameturon (Dpx M6316) and Phytotoxicity of the Major Degradation Product

Abstract

. 1990. Soil persistence of thiameturon (DPX M6316) and phytotoxicity of the major degradation product. Can. J. Soil Sci.70: [485][486][487][488][489][490][491].The persistence of the herbicidal ester 1r4C)thiameturon was studied at different temperature and moisture conditions in three Saskatchewan soils. [n all soils at 20"C and 85% field capacity, the (raC)ester underwent rapid hydrolysis to 1r4C;thiameturon acid. The hydrolysis was over 85% complete in 1 week, and more than 95% complete after 2 wk. The soil degradation of 1r4C;thiameturon acid was considerably slower than that of the parent eiter. Transformation of 1r4C;thiameturon to acid in all soils at85% freld capacity was temperature dependent, being slowest at 10oC, and fastest at 30oC. Conversion to the acid was also moisture dependent. There was no hydrolysis in air-dry soils after 10 wk. At 5O% freld capacity 22% of the ester remained after I wk, and at held capacity less than 27o of the applied ester was recoverable after I wk.Soils treated with thiameturon acid at rates up to 500 pg g -' exhibited no phytotoxicity to canola, lentil, or sugarbeet seedlings. [(a-methoxy-6-methyl-1,3,5-trol of a wide range of broadleaf weeds in triazin-2-yl)amino I carbonyl I amino I cereal crops. sulfonyl l-2-thiophenecarboxylic acid) Thiameturon is non-volatile, possesses a Cissociation constant (pK") of 4.0 in water at 25"C, and at the same temperature has 485 Can.

Degradation of Thifensulfuron Methyl in Soil: Role of Microbial Carboxyesterase Activity

“…In these fresh, nonsterile soils which include a wide range of pH, organic matter, and textural classes, DT 50 s for thifensulfuron range from 0.75-3.5 days. These results are consistent with those of Smith et al (1990) who showed that thifensulfuron methyl degraded with a DT 50 of considerably less than 1 week in three different soils under constant temperature conditions of 10, 20, and 30°C. Cambon and Bastide (1992) found that thifensulfuron methyl degraded with a DT 50 of 1.6 and 1.7 days at 28°C in two soils of pH 6.3 and 7.8, respectively.…”

Leaching of Three Sulfonylurea Herbicides during Sprinkler Irrigation

“…The susceptibility of thifensulfuron‐methyl, tribenuron‐methyl, and rimsulfuron to leach to ground water depends, in part, on their persistence in soil. Thifensulfuron‐methyl has been shown to have a half‐life of <1 wk in laboratory studies involving several nonsterile soil types under various conditions of soil moisture and temperature (Beyer et al, 1987; Smith et al, 1990; Cambon and Bastide, 1992; McDowell et al, 1997; Brown et al, 1997) and in a field study (McDowell et al, 1997). In a laboratory study, the half‐lives of rimsulfuron in soil were 24.5 and 22.2 d under aerobic and anaerobic conditions, respectively, but a shorter half‐life (5.6 d) was observed under field conditions (Schneiders et al, 1993).…”

Microbial hydrolysis of methyl aromatic esters by Burkholderia cepacia isolated from soil

“…For pesticides carrying a methyl ester group, degradation pathways in soil can involve hydrolysis of the methyl ester bond, and lead to formation of the corresponding acids [1–4].…”