## 4 Discussion
### Influence of Tillage Practices on Herbicide Degradation
#### 4.5.3 Cross-Pesticide Comparison of Degradation Efficiency at the Mid-Incubation Period  
The mid-incubation phase serves as a critical time point for evaluating relative differences in degradation rates among various pesticides under uniform tillage conditions. This study reveals that mesotrione consistently exhibited the highest degradation efficiency across all tillage treatments at this stage, highlighting its intrinsic rapid dissipation characteristics and distinct responsiveness to soil management practices. Under CK conditions, mesotrione showed superior degradation efficiency compared to atrazine, acetochlor, and alachlor. Nicosulfuron also demonstrated high degradability, though its rate at this stage was not significantly different from that of mesotrione under CK. Under SS conditions, however, mesotrione's degradation advantage became even more evident, surpassing all other herbicides, including nicosulfuron. This observation suggests a potential synergistic interaction between mesotrione and straw incorporation. Crop straw incorporation can alter soil microbial community composition by introducing abundant labile organic carbon. This change may promote the growth of specific microbial populations capable of degrading mesotrione, potentially accelerating its breakdown [85]. Under ST conditions, mesotrione maintained significantly higher degradation efficiency compared to the strongly adsorbed and slowly degrading chloroacetamide herbicides--acetochlor and alachlor. However, its performance did not differ significantly from that of atrazine or nicosulfuron at this stage. This outcome reflects the complex interactions induced by mechanical soil disturbance. On one hand, ST may have improved soil structure, aeration, and the spatial distribution of straw, which could favor aerobic microbial activity and enhance pesticide degradation. On the other hand, the initial physical disruption caused by rotary tillage might have transiently suppressed or dispersed certain microbial populations, delaying the onset of active degradation. The observed reduction in degradation efficiency differences between mesotrione and some herbicides under ST may be attributed to treatment-specific changes in soil-pesticide-microbe interactions. Similarly, nicosulfuron's consistent degradation pattern suggests a high degree of stability in its dissipation process, even under altered soil conditions imposed by tillage practices. This study demonstrates that the combined effects of tillage regimes and straw management strategies exert profound and differential influences on pesticide degradation dynamics in agricultural soils. These effects are highly dependent on the physicochemical properties of each compound and its dominant degradation pathways. Straw incorporation generally retarded the degradation of hydrophobic compounds such as acetochlor and alachlor, likely due to increased soil organic matter content, enhanced sorption capacity, and reduced bioavailability. In contrast, for compounds that are readily metabolized by soil microorganisms--such as mesotrione--straw acted as a valuable carbon and energy source, promoting the growth of specialized or co-metabolizing microbial communities and thereby accelerating degradation. These findings highlight how different tillage methods can substantially alter the environmental fate of herbicides, influencing their persistence and potential ecological risks [86]. Different tillage methods can substantially impact the degradation of herbicides in soil, affecting their persistence and potential environmental risks [31]. To effectively mitigate pesticide residues in agroecosystems, this study recommends integrating straw incorporation with either ST or SS for atrazine and mesoftrone, given their positive responses to these practices. For persistent herbicides like acetochlor and alachlor, alternative compounds or enhanced degradation strategies should be considered to reduce residual contamination risks.