Physicochemical characterisation of soil amendments derived from residual materials and their effects on soil fertility

This study was conducted to characterise physicochemical properties of residual materials (i.e., rice husk, RRH; rice husk biochar, RHB; maple leaf, RML; maple leaf biochar, MLB; red mud, R.M; and steel slag, S.S) to guarantee the right identification for applying them as soil amendments. In addition, the influence of amendments on soil water holding capacity (WHC) and cation exchange capacity (CEC), as critical factors for soil fertility, was examined. Pyrolysis of RRH and RML at 550°C caused an increase in specific surface area (SSA), aromatic carbon rings and pH of the resultant biochars RHB and MLB. Strong negative zeta potential (ZP) values for RRH, RML and biochars were observed. However, R.M and S.S showed both negative and positive values for ZP depending on the pH condition. Applying RHB, MLB, R.M and S.S as soil amendments for a contaminated site showed promising results to increase soil CEC, WHC and metals immobilisation.