Health Assessment of Natural Selenium-Rich Soil in Yuanzhou District Based on Selenium–Cadmium Principal Factors and the Accumulation of Selenium and Cadmium in the Area Crops

Selenium (Se) is essential for human health, but it interacts with cadmium (Cd). However, there has been little focus on developing soil health evaluation models based on the interaction between Se and heavy metals, or the transport of Se and Cd in oilseed rape. Through detection, it was found that the soil in Yuanzhou District is mostly Se-rich (average 0.62 mg kg−1). Correlation analysis of the soil showed a positive correlation between Se content with Cd (r = 0.62, p < 0.01) and organic matter (r = 0.60, p < 0.01). A soil health score model was developed and performed well, indicating that the model can be used to estimate relevant soil health scores. Furthermore, the natural Se content of rice ranges from 0.07 to 0.28 mg kg−1, and the overall enrichment ability of Se and Cd in oilseed rape is stronger than it is in rice. According to the correlation analysis, the Cd content in the soil was significantly correlated with the stems of oilseed rape (r = 0.49, p < 0.01) and rice (r = 0.37, p < 0.05). As a result, this study suggests using the rice/oilseed rape intercropping model of farming to transfer Cd into oilseed rape to reduce the Cd content in rice.