This paper is the result of agricultural geochemical survey engineering.

Objective As a heavy metal, cadmium (Cd) mainly enters the food chain through the "soil=plant" system and affects human health. It is great significant to study the accumulation of cadmium in crops to ensure human health and safety.

Methods Soil and rice samples from Nanchong, Bazhong and Guang'an in the northeast Sichuan were collected. The cadmium content in soil and rice was analyzed by ICP=MS, and the data were statistically analyzed by CART decision tree and correlation coefficient methods.

Results The research shows that the cadmium content of the soil in the northeast Sichuan is relatively low, ranging from the safety threshold. In contrast, the cadmium content of the rice (brown rice) varies from 0.002 to 0.803 mg/kg and with an average value of 0.076 mg/kg, 14.0% of which is above the safety threshold. The daily cadmium intake of adults reaches 90.4 μg/d in the region with excessive cadmium in rice, exceeding the permissible cadmium intake of 60 μg/d.

Conclusions The phenomenon that cadmium content does not exceed the safety threshold in soil but it does in rice may be related to the characteristics of low pH, low CaO and high SiO₂ of the soil. This recognition is great significance for guiding grain production in this region. 0.071 to 0.92 mg/kg and with an average value of 0.254 mg/kg. The cadmium content of almost all (99.9%) soil samples is below