## 4 Discussion  
### Implications of Pesticide Residue Variability  
For atrazine, compared to previous studies conducted in similar agroecosystems, the observed atrazine levels were significantly lower than those reported in agricultural soils from Liaoning Province (18.38 \(\upmu\)g/kg), riverbank soils of the Songhua River Basin (11.28 \(\upmu\)g/kg), and soils surrounding Xingkai Lake (26.09 \(\upmu\)g/kg) [4,48]. These differences may be attributed to variations in application history, climatic conditions, or soil physicochemical properties that influence herbicide persistence.  
For acetochlor, the corresponding CV of 1.06 suggests substantial spatial heterogeneity in its residual distribution. This level is notably higher than the previously reported acetochlor residues in agricultural soils from Huangdao (10.70 \(\upmu\)g/kg) [49], which could reflect differences in pesticide usage patterns or environmental fate characteristics under varying management practices.  
For alachlor, the high CV of 3.95 indicates highly uneven distribution, possibly due to localized application or differential degradation rates influenced by microsite-specific factors. Neither incosulfuron nor mesotrione was detected in any of the soil samples analyzed, suggesting either limited use, rapid degradation, or low persistence under the prevailing environmental conditions.  
Under CK conditions, the relatively high CV for atrazine under CK suggests significant spatial variability, which may be related to uneven application or limited mixing in no-till systems. Acetochlor showed low CV, indicating a more uniform distribution, possibly due to consistent application practices or stable environmental behavior under CK conditions. The absence of alachlor, nicosulfuron, and mesotrione under CK may reflect rapid degradation, low application rates, or both.  
Under SS treatment, the moderate variability in acetochlor suggests uneven application or localized environmental effects. The detection of alachlor in some samples, along with its high CV, indicates inconsistent presence, possibly linked to differential degradation or application patterns.  
Under ST conditions, higher atrazine residues may reflect increased soil retention or slower degradation under more intensive mixing. Acetochlor showed the greatest variability among all treatments, likely due to higher adsorption or microsite-specific degradation rates. The absence of alachlor, nicosulfuron, and mesotrione under ST suggests either rapid dissipation or limited use under this management system.  
Collectively, these findings indicate that different tillage practices can exert distinct influences on the distribution and persistence of herbicide residues in agricultural soils. The observed variability across treatments highlights the complex interplay among soil physicochemical properties, microbial activity, and tillage-induced alterations in soil structure and moisture dynamics. A deeper understanding of these processes is essential not only for assessing the environmental fate of herbicides but also for evaluating their potential implications for human health and ecosystem safety. Given the detected presence of several herbicides at varying concentrations, it becomes increasingly important to conduct a comprehensive human health risk assessment to determine whether these residues pose unacceptable risks through direct exposure or food chain transfer. Furthermore, elucidating the underlying degradation mechanisms under different tillage regimes is crucial for predicting herbicide persistence and developing effective mitigation strategies. These investigations will provide a scientific basis for optimizing pesticide use and tillage practices, ultimately supporting the design of more sustainable and environmentally responsible agricultural systems.