Impacts of rapeseed dregs on Cd availability in contaminated acid soil and Cd translocation and accumulation in rice plants

The objective of the present study was to investigate the effects of rapeseed dregs (RSD, a commonly organic fertilizer in rural China) at application rates of 0, 0.75, 1.5, and 3.0 % on Cd availability in soil and its accumulation in rice plants (Oryza sativa L., Xiangwanxian 12#, and Weiyou 46#) by means of a pot experiment. The results showed that application of RSD resulted in a sharp decrease in the soil TCLP-extractable Cd content. However, the soil TCLP-extractable Cd content in amended soil gradually increased during the rice growing period. Application of RSD significantly increased Cd transport from root to shoot and the amount of Cd accumulated in the aerial part. RSD was an effective organic additive for increasing rice grain yield, but total Cd content in rice grain was also increased. At an application rate of 1.5–3.0 % RSD, the total Cd content in Weiyou 46# brown rice was 0.27–0.31 mg kg−1, which exceeded the standard safe limit (0.2 mg kg−1) and was also higher than that of Xiangwanxian 12# (0.04–0.14 mg kg−1). Therefore, Weiyou 46# had a higher dietary risk than Xiangwanxian 12# with RSD application. We do not recommend planting Weiyou 46# and applying more than 0.75 % RSD in Cd-contaminated paddy fields.