## 4 Discussion
### Influence of Tillage Practices on Herbicide Degradation
#### 4.5.1 Comparative Degradation of Pesticides Under the Same Tillage Treatment  
Differences in pesticide degradation rates are primarily governed by inherent chemical properties such as molecular structure, water solubility, adsorption behavior, and susceptibility to microbial or chemical degradation processes.  
Nicosulfuron's high liability under typical soil conditions is due to its susceptibility to chemical hydrolysis. In contrast, acetochlor and alachlor, both chloroacetamide herbicides, possess stable molecular structures and exhibit high hydrophobicity, which promotes strong sorption to soil organic matter. This reduces their bioavailability and slows down microbial degradation, leading to prolonged persistence in the soil environment [76; 77]. Atrazine and mesotrione displayed intermediate degradation rates, likely due to a combination of moderate sorption and variable susceptibility to biotic and abiotic degradation mechanisms. Microbial degradation plays a key role in the dissipation of many pesticides, particularly those with moderate to low sorption properties. Microbial degradation plays a key role in the dissipation of many pesticides, particularly those with moderate to low sorption properties. Several bacterial genera--including Bacillus, Micrococcus, Arthobacter, Corynebbacterium, Flavobacterium, Pseudomonas, and Rhodococcus--are well known for their high pesticide-degrading capabilities [78].  
The introduction of SS treatment led to enhanced degradation of mesotrione, which can be attributed to the addition of crop straw, which serves as a carbon and energy source for soil microorganisms, thereby promoting the proliferation of specific microbial communities capable of metabolizing mesotrione [79]. However, the same treatment slowed the degradation of other herbicides, which suggests that straw application may have temporarily immobilized these compounds through increased organic matter content or altered microbial community dynamics, thereby delaying their breakdown. Studies have shown that straw incorporation can shift microbial community structure, favoring copiotrophic bacteria that enhance nutrient cycling and pesticide mineralization under certain conditions [80].  
ST treatment demonstrated complex impacts on different herbicides. Atrazine showed accelerated degradation, while alachlor experienced inhibited degradation. For nicosulfuron and acetochlor, degradation rates under ST fell between those observed under CK and SS, indicating a moderate influence of this tillage method on their dissipation. Mesotrione degraded slightly faster under ST than under CK but slower than under SS, reflecting a combined effect of soil physical disturbance and microbial stimulation induced by subsoiling.  
In summary, these findings illustrate that even under the same tillage regime, herbicides exhibit distinct degradation behaviors, largely dictated by their physicochemical properties and interactions with the soil matrix. Furthermore, different tillage practices--byaltering soil structure, microbial habitat, and organic matter dynamics--can either enhance or suppress pesticide degradation, highlighting the importance of integrating soil management strategies into pesticide risk assessment frameworks.