Degradation of 5-Dialkylamino-Substituted Chlorsulfuron Derivatives in Alkaline Soil

Abstract

Sulfonylurea herbicides are widely used as acetolactate synthase (ALS) inhibitors due to their super-efficient activity. However, some sulfonylurea herbicides show toxicity under crop rotation due to their long degradation time, for example, chlorsulfuron. Our research goal is to obtain chlorsulfuron-derived herbicides with controllable degradation time, good crop safety and high herbicidal activities. Based on our previously reported results in acidic soil, we studied the degradation behaviors of 5-dialkylamino-substituted chlorsulfuron derivatives (NL101–NL108) in alkaline soil (pH 8.39). The experimental data indicate that addition of the 5-dialkylamino groups on the benzene ring of chlorsulfuron greatly accelerated degradation in alkaline soil. These chlorsulfuron derivatives degrade 10.8 to 51.8 times faster than chlorsulfuron and exhibit excellent crop safety on wheat and corn (through pre-emergence treatment). With a comprehensive consideration of structures, bioassay activities, soil degradation and crop safety, it could be concluded that 5-dialkylamino-substituted chlorsulfuron derivatives are potential green sulfonylurea herbicides for pre-emergence treatment on both wheat and corn. The study also provides valuable information for the discovery of new sulfonylurea herbicides for crop rotation.

Synthesis, Herbicidal Activity, Crop Safety and Soil Degradation of Pyrimidine- and Triazine-Substituted Chlorsulfuron Derivatives

“…The culture method was consistent with our previous reports [ 11 , 12 , 13 , 14 , 15 , 23 ]. The detailed experimental procedure can be found in the Supplementary Materials (SI) .…”

“…In this study, wheat (Xinong 529) and corn (Xindan 66) were used as test crops, and chlorsulfuron was used as control. The culture method was consistent with previous reports [ 15 , 23 , 27 ].…”

“…Nicholls et al reported that the DT 50 of chlorsulfuron could be 18 months in soil with low microbial activity and a high pH [ 10 ]. Li reported that the DT 50 of chlorsulfuron was 158 days at pH 8.39, and DT 50 of diethylamino-substituted chlorsulfuron was 6.39 days [ 15 ].…”

“…In our previous study, we found that the 5th substituted groups on the benzene ring in chlorsulfuron has a great influence on its degradation rate in acidic soils and concluded for the first time that electron-donating substituents could accelerate degradation rates in acidic soil ( Figure 1 ) [ 11 , 12 ]. Li et al found that 5-dialkylamino-substituted groups on the benzene ring of chlorsulfuron could greatly accelerate degradation under alkaline conditions [ 13 , 14 , 15 ]. However, they found that 5-dialkylamino-substituted groups on the benzene ring of chlorsulfuron could endanger the normal growth of wheat and corn through post-emergence treatment [ 15 ].…”

“…Li et al found that 5-dialkylamino-substituted groups on the benzene ring of chlorsulfuron could greatly accelerate degradation under alkaline conditions [ 13 , 14 , 15 ]. However, they found that 5-dialkylamino-substituted groups on the benzene ring of chlorsulfuron could endanger the normal growth of wheat and corn through post-emergence treatment [ 15 ]. At the same time, they found that heterocyclic amines-based 5-dialkylamino-substituted chlorsulfuron derivatives could improve crop safety of wheat [ 14 ], and the crop safety of corn with diethylamino-substituted chlorsulfuron was better than that of dimethylamino-substituted chlorsulfuron through pre-emergence treatment [ 15 ].…”