Abstract: In this study, we evaluated the efficiencies of remediation of Cd contaminated soil by bone charcoal (BC) and seaweed fertilizer (SF) simultaneously in pot and field experiments by determining the Cd reduction rates (%) for wheat, maize, sorghum grain and tobacco leaves, the DTPA-extracted fraction of Cd in soil and remediation marginal efficiency (ME). The results indicated that Cd uptake by and translocation in different crops were significantly reduced (P<0.05) by the application of soil amendments. In field experiment, compared with control (CK), the Cd reduction rates for crop grain or tobacco leaves were 16.2%39.8%. Amendment application led to increase of crop productivity by 12.3%38.6%. The amount of increase depended on crop species; in this study wheat yield had the largest increase after BC application. Adding biofertilizer promoted the formation of large aggregates with higher Cd load by mass, and increased soil pH by 0.430.77 units compared with control. We believe the re-distribution of Cd in soil aggregates and increased soil pH due to amendments were responsible for immobilizing soil Cd and alleviating its phytotoxicity. The remediation marginal efficiency for the test soil ranged from 3.99% to 14.74%, with the highest ME observed for BC followed by SF treatments. In pot experiment, different amendments had bigger remediation effects than in field validation experiment, which might be due to larger root system in field soil limiting the remediation efficiency of amendments.

Key words: Cd, bone charcoal, seaweed fertilizer, Cd reduction rate, remediation marginal efficiency