Abstract
Soil health is essential for sustainable agriculture but is increasingly threatened by the co-occurrence of pesticides and heavy metals from agricultural and other anthropogenic activities. Although individual contaminants are well studied, their interactions in arable soils remain insufficiently understood. This review synthesises evidence on metal–pesticide interactions, focusing on complexation, adsorption, sorption competition, degradation, speciation, and toxicity, and examines how contaminant properties and soil physicochemical conditions regulate these processes. The evidence shows that interactions can be additive, synergistic, or antagonistic, depending on factors such as contaminant combinations, soil pH, organic matter, mineral composition, and microbial activity. Metals may modify pesticide degradation, while pesticides can alter metal partitioning, speciation, and availability through complexation and changes in soil chemical processes. These interactions can consequently influence microbial communities, soil enzyme activities, nutrient cycling, and plant responses. However, substantial variability in experimental conditions and limited long-term field evidence restrict the prediction of interaction outcomes under realistic agricultural conditions. From a soil-management perspective, assessment of co-contaminated soils should therefore consider contaminant mixtures, soil properties, chemical speciation, and bioavailable fractions rather than total concentrations alone. Future research should prioritise environmentally realistic mixtures, long-term field studies, transformation products, and integrated microbial, plant, and ecotoxicological endpoints to strengthen risk assessment and management of co-contaminated arable soils.