Application of Soil Remediation Techniques: A Case Study of Rice in a High-Selenium and High-Cadmium Soil Background Area in the Enshi Area

Seeking effective measures for the improvement of high-selenium and high-cadmium soils holds significant theoretical and practical importance for sustainable agricultural development. This paper focuses on conducting a site-specific soil survey in the characteristic agricultural product production area of Hefeng County, Enshi Prefecture, Hubei Province. Through field experiments, we compared 14 soil improvement methods across three techniques: chemical passivation remediation, agronomic regulation, and microbial remediation. The study investigated their impacts on rice Cd content, rice Se content, yield, and quality and conducted a comprehensive evaluation of the remediation effects of the different treatments. The experimental results indicate that (1) increasing the content of soil conditioners can enhance rice yields, with Treatment 14 showing the most significant increase, yielding an additional 257.3 kg per mu, representing a 55.62% increase. Treatment 12 also demonstrated a notable yield increase of 95.1 kg per mu, or a 20.55% increase. Lime, sepiolite, and shell powder can effectively reduce rice’s absorption of Cd. Treatment 9 resulted in the lowest Cd content in the rice, at 0.03 mg/kg, with a Cd reduction rate of 92%. The optimal application rates for this Cd reduction were 200 kg/mu of lime, 125 mL/mu of foliar inhibitor, and 50 kg/mu of carbon-silicon fertilizer. Treatment 12 achieved a rice Cd content of 0.11 mg/kg, with a 70% reduction in Cd, bringing the rice Cd content down to below 0.2 mg/kg, which meets the requirements of the National Food Safety Standard: Maximum Levels of Contaminants in Foods. In the comprehensive scoring of all treatments, considering four evaluation indicators—rice Cd content, rice yield, rice quality, and cost—Treatment 12 (300 kg/mu of soil conditioner + 50 kg/mu of carbon-silicon fertilizer) was found to be the optimal treatment through comparative scoring. It demonstrates good potential for ensuring safe rice production and can serve as a reference standard for repairing Cd-contaminated rice paddies in the local area, with promotional value.