Effects of Different Remediation Treatments and Rice Intercropping on the Integrated Quality of Paddy Soils Mildly Contaminated by Cadmium and Copper

The issue of soil contamination by heavy metals (HMs) has attracted extensive attention. In the present study, the effects of four remediation measures combined with rice intercropping on the quality of soils were evaluated in a mildly HM-contaminated paddy field. The results showed that better comprehensive remediation effects were found in the intercropping system with high and low Cd-tolerant rice than in the monoculture system. Both foliar spraying of sodium selenite and inoculation with Pseudomonas TCd-1 significantly reduced the Nemerow comprehensive pollution index (NCPI) of the soils. The application of biochar and lime significantly increased the soil fertility index. Among all the treatments, the application of 30 t∙hm−2 biochar and 3600 kg∙hm−2 lime improved soil fertility the most. The lowest single-factor pollution indices (SFPIs) of Cd, Cu, Zn, Ni and Pb and the NCPI of the soils were observed in the treatment with foliar spraying of sodium selenite at 45 mg∙L−1, showing the greatest comprehensive reduction in soil HMs. The application of 1200 kg∙hm−2 lime and 30 t∙hm−2 biochar and foliar spraying of 45 mg∙L−1 sodium selenite effectively improved the soil quality. Overall, the soil quality of paddy fields dramatically influenced the cleaner production of rice and is of great significance to the maintenance of food security.