Sustainable Biochar Effects on the Bioavailability of Heavy Metals: A 2-Crop Season Site Practice Near a Lead-Zinc Smelter in Feng County, China

Abstract

It is of great significance to explore the remediation pattern in heavy metal (HM) contaminated soil under the actual farming mode. This field trial was carried out under the rotation condition s (soybean-rape, corn-wheat) lasting for a 2-crop season near a lead-zinc smelter, exploring the effect of biochar on the physical and chemical properties of rhizosphere soil, crop yield, total and different forms of HMs in soil, and the HM accumulation by crops. No significant change in pH in soil was observed, as did the EC values with a low dose of biochar added. The contents of TK increased by 0.87% ~ 28.2% with the biochar addition compared with the controls. The effect of high-dose biochar on increasing the nutrient elements in soil was obvious. Additionally, the contents of soil total humic carbon(THC) increased significantly ( P < 0.05) by 3.7% ~ 72.7%. The yield of first season crops (soybean and corn) increased by 30% ~ 42% and 34% ~ 61% respectively, as did the second season crops of rape (25% ~ 41%) and wheat (9% ~ 29%). Furthermore, the reduction in the availability form (F1+F2) of Cd and Pb was 1.07-10.0% and 2.92-8.35%, respectively, while there was a tendency of Zn to increase. The biochar addition led to significant differences in the soil total contents of HMs. The contents of HMs accumulated by crops increased, although biochar significantly ( P < 0.05) decreased the total contents of Pb and Zn in soil.The Cd, Pb and Zn accumulation in stems and leaves of crops was higher than that in roots. This study helped clarify the sustainable effect of biochar on the bioavailability of HMs under rotation conditionsand could be used to guide the remediation of contaminated soil in actual mining areas.