Cd胁迫下城郊农业土壤微生物活性对生物炭输入的响应

为了探究Cd胁迫下生物炭输入对城郊农业土壤微生物活性的影响,通过室内培养试验,分析CK处理(风干土壤)、Cd处理(风干土壤+外源Cd)、CdBC处理〔风干土壤+外源Cd+2%生物炭,即生物炭与土壤(以湿质量计)质量比为2%〕、BC处理(风干土壤+2%生物炭)对土壤呼吸、土壤微生物数量及土壤酶活性的影响. 结果表明:整个培养期(0~60 d)内,各处理下土壤CO₂累积释放量表现为CK处理＜Cd处理＜CdBC处理＜BC处理. 与CK处理相比,CdBC处理下生物炭输入能显著增加土壤CO₂累积释放量(P＜0.05),增幅为43.6%,并且土壤中细菌、放线菌、真菌数量也有显著增加(P＜0.05),增幅分别达到12.7%、62.7%、18.7%. Cd胁迫对土壤酶活性的抑制表现为蔗糖酶＜脲酶＜中性磷酸酶,抑制率分别为3.5%、6.8%、18.0%. 生物炭输入可使受Cd胁迫的土壤脲酶、蔗糖酶的活性有所增强,增幅分别为15.0%、18.4%. 可见,生物炭输入可在不同程度上缓解Cd胁迫对蔗糖酶、脲酶活性及土壤微生物数量的影响. 

Responses of Agricultural Soil Microbial Activity to Biochar under Cadmium Stress

Due to its special physiochemical properties, biochar plays an important role in many aspects of soil, because biochar has an impact on both plant growth and soil microorganisms. This study mainly focuses on the responsive changes of soil microbial activity under the condition of the interaction between biochar and heavy metals. By using the indoor incubation method, a single treatment of 2% biochar and Cd (6.55 mg/kg), as well as their combined treatment, was investigated to determine their influence on the activity of soil microorganisms, including soil respiration, amount of soil microbes (bacteria, actinomycetes and fungi), urease, neutral phosphatase and invertase. The results demonstrated that when the incubation finished, the total CO₂ emission among all treatments showed the following sequence:control soil＜soil+Cd＜soil+Cd+biochar＜soil+biochar. Compared with the CK treatment, when the content of Cd in soil was 6.55 mg/kg, the input of biochar significantly enhanced CO₂ emission of the soil by 43.6% (P＜0.05). In particular, after the biochar was amended, a significant increase (P＜0.05) in number of bacteria, actinomycetes and fungi in the soil was observed, with the maximum amplitudes reaching 12.7%, 62.7% and 18.7%, respectively. Cd exhibited a varying level of inhibiting effect on the activity of soil enzymes; the sequence of inhibition degree from low to high was invertase, urease and neutral phosphatase, with the inhibition rates reaching 3.5%, 6.8%, and 18.0%, respectively. While the input of biochar positively affected the activity of soil urease and invertase, the increase amplitudes were 15.0% and 18.4%, respectively, compared to the Cd treatment. In conclusion, the amended biochar could alleviate the stress caused by Cd on numbers of soil microbes and enzymatic activities except for neutral phosphatase to different degrees.