Objective The aim was to explore the remediated materials for cadmium (Cd)-contaminated soil-rice and shrimp breeding system.

Methods The rice and shrimp fields in Southern China were selected, and 6 different treatment types of foliar fertilizer and bamboo charcoal organic fertilizer and their combinations were designed, including CK (check), T1 (foliar spray with selenium fertilizer) and T2 (foliar spray with selenium fertilizer + L-cysteine), T3 (bamboo charcoal organic fertilizer), T4 (bamboo charcoal organic fertilizer + selenium fertilizer) and T5 (bamboo charcoal organic fertilizer + L-cysteine). Soil pH value, soil organic matter (SOM), Cd forms in soil, Cd content in different parts of rice and crayfish were determined. The Cd pollution risk values of soil, rice and crayfish were evaluated by the integration index, mobility index, potential ecological risk index and dietary risk index, respectively.

Results Soil pH value and SOM in T3 - T5 treatments were significantly increased compared with the CK, and the increase rates were 5.71% - 6.12% and 3.28% - 4.23%, respectively. The contents of DTPA-extracted Cd decreased significantly, and the decreasing rates were 18.46%, 19.81% and 17.59%, respectively. The Cd distribution proportion in acid extraction in soil decreased significantly, and the distribution proportion in residual forms increased significantly, which effectively reduced the bioavailability and migration of Cd in soil. In addition, the contents of Cd in roots, stalks, leaves and seeds under T1-T5 treatments decreased significantly compared with CK treatment, by 18.28% - 84.68%, 26.92% - 93.08%, 21.79% - 88.46% and 27.76% - 96.84%, respectively. The order of dietary risk index and potential ecological risk index was CK > T3 > T1 > T2 > T5 > T4.

Conclusion The application of bamboo charcoal organic fertilizer plus leaf surface inhibitor has better Cd reduction effect, which is more conducive to ensure the safety of rice.