Effects of Two Kinds of Biochars on Soil Cu Availability in Contaminated Soil

This paper is aimed to research the impacts of different biochars(0,1%,2%,4%), including maize biochar and phytolacca root biochar, on rape growth and the soil Cu availability in the Cu-contaminated red soil via a series of pot experiments. The results showed that, compared with the control, the addition of two kinds of biochars could increase the biomass of the rape. In low Cu-contaminated red soil, added 4% maize biochar and phytolacca root biochar increased the biomass by 21.2 times and 67.9 times; however, the biomass were increased by 8.6 times and 109.6 times under high Cu-contaminated soil. The addition of phytolacca root biochar could increase the soil pH significantly, which has been increased by 0.4~1.6 units with the addition of phytolacca root biochar in low Cu-contaminated red soil, and it had 0.25~1.35 units more than that with maize biochar; In high Cu-contaminated red soil, with the addition of phytolacca root biochar, soil pH was increased by 0.33~1.52 units, which was 0.3~1.25 units higher than maize biochar. There was a significant effect on reducing the soil Cu availability with the addition of the two biochars. Among them, 4% addition of maize biochar and phytolacca root biochar could reduce soil available Cu content by 21.9% and 45.2% in low Cu-contaminated soil, however, it was decreased by 41.9% and 53.8% in high Cu-contaminated soil. Both of the two biochars were able to reduce the Cu accumulation in rape, where there was a decrease by 21.2% and 67.8% with he addition of 4% maize biochar and phytolacca root biochar under low Cu-contaminated soil, and it was decreased by 19.9% and 66.8% in high Cu-contaminated soil respectively. Both of the biochars could ameliorate the acidity and Cu availability in the red soil, enhance the biomass of the rape and reduce the Cu accumulation in rape, but phytolacca root biochar had more effective influence than maize biochar.