The Effect of Bamboo Charcoal Application on Soil Nutrients and Heavy Metals in Rice

Soil heavy metal pollution is becoming more and more serious. Biomass charcoal application can play an important role in alleviating the toxicity of heavy metals in soils. Compared with other biochar, bamboo charcoal has more unique properties and may have a unique effect on heavy metal pollution. Zhejiang Province of Southeastern China is rich in bamboo resources. However, few studies related to bamboo charcoal application for heavy metal remediation in farmland were reported. In this study, four treatments with different amounts of bamboo charcoal application were set up through a field experiment, namely BC0 (no bamboo charcoal application), BC1 (2500 kg⋅ha⁻¹), BC2 (5000 kg⋅ha⁻¹), and BC3 (10000 kg⋅ha⁻¹), and each treatment was replicated three times. The results showed that (1) The application of bamboo charcoal significantly increased the soil pH and organic matter content. Compared with BC0, the pH and organic content of BC3 increased by 7.4% and 17.4% (P < 0.05) respectively. (2) The HCl-extractable Cd content of paddy soil in the BC1 treatment was significantly lower than other treatments (P < 0.05), and decreased by 15.3%, compared with BC0. The soil HCl-extractable Zn and Cu content did not differ significantly between treatments (P > 0.05). (3) With the increase of bamboo charcoal application, the Cd content in rice gradually decreased, the BC3 treatment significantly decreased by 39.0% (P < 0.05), and the Zn and Cu contents in rice did not differ significantly between treatments (P > 0.05), compared with BC0. (4) Soil pH, organic matter and Cd in rice seeds were significantly negatively correlated (P < 0.01). The heavy metal content in rice does not change with the change of heavy metal content with HCl-extractable state in soil. It means bamboo charcoal does not reduce heavy metal content in rice by simply declining the heavy metal content with HCl-extractable state. The mechanism of action is relatively complicated, and further study is needed.