Abstract

Total cadmium (Cd) concentrations in soils from fallow (A) and rice cultivated field (B) both below detection limit, indicated a plausible ‘pristine’ nature of the sites. The soils were individually spiked with 10 mg/kg CdCl2.H2O and other fractions were amended with oilseed rape biochars (OSR) produced at 550°C and 700°C in triplicates and then incubated for 60 days. During cultivation in soil B, mycorrhical fungi were inoculated in the field and this led to increased levels of phosphates (219.33 mg/kg) compared to the fallow soil A (5.33 mg/kg). The biochars slightly differed in physico-chemical properties and their influence on extraction behaviour of Cd was tested. Following 60 days ageing period, mean values followed the order of HNO3 > EDTA > CaCl2 in the soil samples. However, OSR550 significantly reduced the EDTA (1.48 mg/kg) and CaCl2 (0.86 mg/kg) extractable fractions which represent the potentially mobile and mobile fractions, respectively of Cd in soil A. The phosphate content of soil B ensured the precipitation of Cd to reduce the mobile fractions as well. Nevertheless, biochar showed to reduce mobile fractions much more than the naturally acquired phosphate soils. Biochar production showed to be a valuable tool to mitigate mobility of toxic Cd content in phosphate deficient soil.