## 4 Discussion
### Influence of Tillage Practices on Herbicide Degradation
#### 4.5.2 Degradation Responses of Individual Pesticides to Different Tillage Treatments  
The interaction between tillage practices and straw management strategies exerted highly differentiated effects on the degradation dynamics of individual herbicides, reflecting both pesticide-specific physicochemical properties and tillage-induced alterations in soil environmental conditions. For atrazine, significant differences were observed across the three tillage regimes. The SS treatment notably delayed degradation, whereas the ST treatment maintained or slightly accelerated it. These findings suggest that ridge-based straw mulching may reduce atrazine bioavailability through enhanced adsorption or altered microbial activity, while rotary tillage under ST likely promotes degradation via improved soil aeration and mixing [81]. Degradation kinetics revealed distinct temporal patterns under different tillage treatments. Under ST, atrazine degradation began more rapidly compared to CK and SS, indicating enhanced early-stage dissipation. A marked increase in degradation rate was also observed during the mid-to-late incubation phase, resulting in high final degradation efficiency. In contrast, CK showed slower initial degradation but still achieved near-complete breakdown by the end of the observation period, highlighting the resilience of atrazine biodegradation under conventional management practices. Both acetochlor and alachlor, classified as chloroacetamide herbicides, exhibited similar responses to the tested tillage treatments. Straw incorporation prolonged their degradation times under both SS and ST regimes, indicating increased persistence in the soil environment. Degradation patterns revealed that acetochlor was relatively stable over time, with minimal variation across treatments, suggesting that tillage had limited impact on its overall dissipation. In contrast, alachlor showed distinct differences in early-stage degradation, with the ST treatment promoting faster initial breakdown. However, degradation rates tended to converge in later stages, resulting in generally low final degradation efficiencies. These observations suggest that while certain tillage practices may temporarily enhance alachlor degradation, long-term suppression occurs, potentially due to straw-induced adsorption or microbial inhibition. For nicosulfuron, the SS treatment significantly delayed degradation, while the ST treatment resulted in an intermediate effect. Kinetic analysis revealed a consistent and gradual increase in degradation over time across all treatments, with no statistically significant differences among them. By the end of the observation period, degradation exceeded 95% in all cases, indicating that although straw incorporation, particularly under SS, may initially slow down degradation through adsorption or microenvironmental changes, nicosulfuron's high susceptibility to hydrolysis and microbial degradation [82] ensures near-complete dissipation regardless of the tillage method. Mesotrione exhibited the most distinctive response to tillage practices among the five herbicides. Degradation was markedly accelerated under SS, while ST also promoted a faster degradation rate compared to CK. Degradation kinetics demonstrated rapid breakdown under both CK and SS during the early stage, whereas degradation started more slowly under ST. This trend persisted throughout the incubation period. The slower initial degradation under ST could be attributed to mechanical disturbance affecting microbial community structure or altering the spatial distribution of straw, which might have temporarily hindered microbial access to mesotrione [83; 84]. Nonetheless, high final degradation efficiency was eventually achieved, underscoring the adaptability of microbial populations to changing soil conditions induced by subsoiling. In summary, the degradation behavior of each herbicide responded uniquely to the applied tillage and straw management strategies.