Biochar and Phosphate Application in a Cadmium-Contaminated Soil: a Strategy to Reduce Cadmium Transference to Rice Plants

Biochar is a soil conditioner that has the potential to remediate soil contaminated with cadmium (Cd). However, the effectiveness of biochar in soil remediation depends on a series of physical, chemical, and biological conditions. Similar to the effect of biochar, phosphate may also promote Cd immobilization in soil, and the vital role of phosphorus (P) in supporting plant growth and yield is well known. In this context, we aimed to evaluate rice (Oryza sativa L.) growth and the P and Cd contents in plant tissues under the combined application of biochar and phosphate as a strategy to mitigate the adverse effects of Cd on rice grown in contaminated soil. A pot experiment was carried out in a greenhouse in a completely randomized design, in a 2 x 2 x 2 factorial scheme, where P and Cd were applied in combination and individually to the soil with and without biochar of Eucalyptus. The combined application of biochar and P reduced Cd content in rice shoots. Higher pH was observed in soils treated with biochar, which might explain, together with the adsorptive capacity, the lower extraction of Cd in soils treated with biochar. However, an increase in P content in the tissue, number of tillers, and biomass production in rice was recorded only under P application. Our findings suggest that biochar and P combined application in Cd-contaminated soils can mitigate the adverse effects of Cd in rice tissues.