Degradation dynamics of Trifluralin in Qinghai-Tibet Plateau and screening of its degrading strains

Trifluralin (FLL) is extensively used in rapeseed fields in the Qinghai-Tibet Plateau (QTP) region. However, the degradation kinetics of FLL in this area and its impact on environmental microbial communities are not yet known. To investigate the degradation patterns and ecological benefits of FLL, this study established a comprehensive method for detecting FLL residues and selected efficient degrading bacterial strains. Degradation experiments were conducted in two typical soil types of the QTP, and the dynamic changes in microbial communities were explored. The results indicated that FLL degradation in soils from two different regions of the QTP followed first-order kinetics, with half-lives of 25 and 39 days, respectively. The application of FLL at 173 g/ha significantly increased bacterial richness and diversity in the soils of both regions. Three efficient degrading strains were selected from soil samples: FL-3 (<i>Bacillus velezensis</i>) with a degradation rate of 80.81 %, FL-5 (<i>Bacillus velezensis</i>) at 51.18 %, and FL-6 (<i>Pseudomonas atacamensis</i>) at 49.98 %. Moreover, the optimal degradation conditions for these strains were determined, and it was verified that they had no adverse effects on the germination and seedling growth of rapeseed, wheat, and barley. The findings of this study provide important data for the environmental risk assessment of FLL and suggest potential biological resources for the rational use and environmental remediation of this herbicide. These results are significant for developing safe use and environmental management strategies for FLL in the QTP.