Biochar combined with phosphate fertilizer application reduces soil cadmium availability and cadmium uptake of maize in Cd-contaminated soils

Cadmium (Cd) has become the primary pollution factor in farmland, which seriously threatens crop growth and food safety. A pot experiment was conducted to investigate the effect of combined application with biochar and P fertilizer on soil Cd availability and translocation, in which biochar was 0 (C0) and 20 g kg−1 (C20), P fertilizer was 0 (P0), 20 (P20), and 40 mg P kg−1 (P40). Results showed that, compared with C0 level, the content of DTPA-Cd in soil was significantly decreased with biochar addition after 60 days of cultivation, under C20 level, soil DTPA-Cd in C20P40 treatment were significantly increased. Under both C levels, the percentage of exchangeable Cd fraction at P40 rate was significantly lower than that at P20 rate, because the excess P in soil could precipitate Cd. The percentage of residual-Cd fraction was significantly increased with the combined addition of biochar and P fertilizer, particularly in C20P40 treatment, which was 75.95%, while it was only 61.65% in C0P0 treatment. The Cd translocation factor (TF) and bioconcentration factor (BCF) were also significantly reduced in C20P20 and C20P40 treatments compared with C0P0 treatment. Therefore, the combined high P and biochar application was a good choice in inhibiting soil Cd availability and plant Cd uptake, which benefited to the safe utility of the Cd contaminated soil.