A laboratory experiment was carried out to evaluate the hexavalent chromium reduction as affected by organic carbon amendment, Mn2+ and microbial activity. Samples of a Hapludult soil (50 g) were placed in plastic bags (50 g) and incubated during 42 days with lime (2.0 Mg ha-1), Cr6+, cattle manure(organic carbon) and Mn2+ in the doses of 20, 50 and 40 mg kg-1, respectively. Half the samples were sterilized by autoclaving to eliminate biological activity. Cattle manure and Mn sulfate amendment promoted a total soil hexavalent chromium reduction (Cr6+ → Cr3+), during the 42-day period. The quadratic and exponential models were the best to describe the Cr6+ reduction with time. The microbial activity increased this reduction in 16%, in the cattle manure treatment without sterilization. The soil Cr6+ contamination may be eliminated by simple organic matter amendment and by maintaining biologic activity.
cattle manure; pH; manganese