Effects of different cadmium sources and biochar application on the cadmium uptake of tobacco plant

Biochar amendment improves the physical and chemical properties of soil as well as functions as a protection mechanism for heavy metal pollution of soil. The purpose of this thesis is to investigate the effect of biochar on cadmium (Cd) uptake of tobacco plant under different Cd forms and application rates. Three different cadmium forms {3(CdSO4).8H2O, Cd(NO3)2.4H2O and CdCl2} and 4 different cadmium doses (0, 2.5, 5.0 and 10 mg Cd kg-1 soil) were applied together with two different mahalep biochar treatments (BC0-%0 and BC1-%1 w/w). Soil DTPA-extractable Cd concentrations and shoot Cd concentrations (P<0.01) were significantly increased with biochar doses, but shoot dry matter yield (P<0.01) was significantly reduced. Soil and plant Cd concentrations were reduced by biochar treatments in all Cd forms and doses. The greatest average reduction in Cd uptake was observed in CdCl2 (170% reduction) and the least reduction was in CdNO3 (27% reduction) forms. Biochar treatments resulted in higher shoot dry matter yields in all Cd forms and doses. The average shoot dry matter yield of 3(CdSO4).8H2O form was 4.85 g plant-1 at BC0 treatment and the value increased to 5.86 g plant-1 at BC1 treatment. Such a case was also valid for the other Cd forms. Average dry matter yield of Cd(NO3)2.4H2O form increased from 4.77 to 5.40 g plant-1 and the value of CdCl2 form increased from 5.15 to 5.54 g plant-1. Regardless of Cd forms, it was concluded that biochar reduced Cd uptake of tobacco plants.