Effects of Soil Amendment Calcium Carbonate and Chiral Pesticide Tetraconazole on the Residues of Pesticide and Cadmium in Rice

Calcium carbonate (CaCO3) is a common soil amendment to alleviate cadmium (Cd) transformation and accumulation in brown rice, and tetraconazole is a widely used chiral pesticide to control rice sheath blight. This study investigated the effects of soil amendment CaCO3 and chiral pesticide tetraconazole on pesticide residues, Cd accumulation, and soil microorganisms in two rice cultivars (ZG 96 with low Cd accumulation and ZY 18 with high Cd accumulation) in Cd-contaminated paddy fields. Results showed that CaCO3 significantly reduced Cd concentrations in brown rice by 60.0–82.9%. It altered tetraconazole degradation half-lives in rice plants, increased residues in ZG 96 rice husk, and decreased enantioselectivity in soil. Tetraconazole residues in brown rice were lower in ZY 18 than in ZG 96. Both CaCO3 and tetraconazole reshaped soil microbial diversity, community structure, and metabolic functions, with distinct responses between the two rice cultivars. All residues of tetraconazole and Cd in brown rice were below maximum residue limits. The rice cultivar differences should be considered under the application of amendments and chiral pesticides, and this study would provide valuable data and theoretical basis for their combined treatments.