Precise and differentiated solutions for safe usage of Cd-polluted paddy fields at regional scale in southern China: Technical methods and field validation.

Cadmium (Cd) contamination in rice grains has become a severe issue worldwide. This study aims to explore feasible technologies applicable to different risk lands and develop a practical solution for safe rice production at a regional scale. Despite inconsistent field conditions in the whole region, various foliar fertilizers could effectively decrease grain Cd content by 20.4-41.6 % and were capable of producing safe grains in low/medium-risk areas. At high-risk sites, foliage dressing coupled with alkaline fertilizers significantly reduced Cd accumulation and increased grain compliance rate to 95.0 %. The cost analysis and questionnaire survey showed the above technologies are low-cost, eco-friendly, and highly acceptable in real-world scenarios. The classification results by conditional inference tree (CIT) for CK and FS scenarios indicated grain Cd content is closely related to the interaction effects of soil Cd and pH. On these bases, the whole area was divided spatially into three different risk zones, and each zone matched a feasible method for safe production, subsequently developing a precise and differentiated solution. The estimation results demonstrate it can effectively improve the precision level of safe utilization of regional polluted lands and save more than half of the total cost, providing a new idea for regional Cd-polluted paddy fields management strategies.