Quantitative Relationship Between Paddy Soil Properties and Cadmium Content in Rice Grains

Abstract

Rice is a crop with the potential for high accumulation of Cd, which can be affected by many factors. Sixty pairs of soil and rice samples from different plots were collected and analyzed, in order to understand the quantitative relationships between the Cd content in soil and the properties of soil and the Cd content in rice grains under field conditions, by simple and multiple regression analyses. The results showed that the Cd contents in soil and rice grains ranged from 0.15-2.54 mg·kg-1 and 0.02-2.00 mg·kg-1, respectively. According to the result of simple regression analysis, there were significantly positive correlations (P<0.01) between the Cd contents in soil and rice grains (r=0.392); the pH, SOM, and CEC in soil also had certain effects on Cd accumulation in rice grains, which were not significant, however. When the soil pH was<6.5, the Cd content in rice grains increased with increasing soil pH, but decreased with increasing soil pH when the soil pH was>6.5. The Cd content, pH, SOM, and CEC in the soil and the Cd content in rice grains were analyzed by multiple regression analysis, and five equations, which all reached extremely significant levels (P<0.01), were obtained. The equation that included the four variables (Cd content, pH, SOM, and CEC in soil) had the most r, and it could predict the Cd content in rice grains better, given the conditions of the present study.