Supported by the National Science & Technology Program of China (No. 2013BAD11B01) and the Outstanding Scientific and Technological Innovation Team Projectof Jiangsu Higher Education Institutions (No. CXLX13_385)
高氮投入的设施蔬菜地土壤易发生次生盐渍化、酸化、板结化等土壤退化现象，也会引起地下水污染、N2O大量排放等环境后果，严重影响了蔬菜农业的可持续发展。强还原土壤灭菌（Reductive Soil Disinfestation, RSD）作为新兴的退化设施蔬菜地土壤修复方法，能够有效缓解土壤退化，但也导致N2O大量排放。本研究选用生物炭作为调节剂，评估不同生物炭施加量对退化设施蔬菜地土壤及其强还原修复过程中N2O排放的影响，并测定反硝化功能基因（一氧化氮还原酶基因norB和氧化亚氮还原酶基因nosZ）丰度来反映反硝化微生物活性。结果显示：RSD法显著降低了土壤硝酸盐含量、提高了土壤pH，缓解了土壤退化，但其N2O累计排放量是非修复土壤的950倍以上；施加生物炭具有减排效果，其中施加5%的生物炭显著降低了退化设施蔬菜地土壤及其强还原修复过程中的N2O排放，其减排量分别为68.7%和16.0%；Pearson相关分析显示，非强还原修复过程和强还原修复过程中土壤N2O排放速率均与pH显著负相关，而在强还原修复过程中土壤N2O排放速率还与NO3--N含量显著正相关；施加生物炭显著改变了土壤norB和nosZ基因，线性回归分析表明，非强还原修复过程和强还原修复过程中土壤N2O排放的微生物机理不同，前者显著受nosZ基因丰度影响，而后者显著受norB基因丰度影响。在退化设施蔬菜地土壤中施加5%生物炭可有效减低退化设施蔬菜地土壤及其强还原修复过程中的N2O排放。
Excessive application of nitrogen fertilizers in facilitated vegetable fields may easily lead to soil degradation (such as soil salinization，acidification，hardening, etc.), and even further to some serious environmental consequences like pollution of groundwater and emission of large volumes of N2O, thus seriously affecting sustainable development of the vegetable industry. Recently, a novel soil remediation technology, called RSD(reductive soil disinfestation) has been developed of adding organic substances (e.g., crop straw, molasses, manure, etc.) in flooding water. The RSD method can effectively alleviate the risk of soil degradation, such as removing the nitrate accumulated in the soil, increasing pH, lowering soil electrical conductivity and improving soil structure. However, in strong reducing environments the high amount of nitrate accumulated in the degraded facilitated vegetable fields was rapidly reduced by denitrification, and high nitrous oxide (N2O) emission was observed in RSD process. N2O is the third major greenhouse gas, and is 296~310 times as high as CO2 in global warming potential. It is estimated that N2O emitted from agricultural soil accounts for 60% of the annual anthropogenic emission into the atmosphere, and the facilitated vegetable soil with high N input is one of the most important agricultural N2O sources, contributing about 20% to the emission from agricultural soil. Therefore, it is essential to investigate how to mitigate N2O emission from degraded facilitated vegetable soil, especially in its strong reductive remediation process. In this study, Biochar was selected as soil regulator in evaluating effects of the use of biochar on N2O emission in degraded vegetable soil and its RSD process relative to rate of its use. Six treatments were designed and conducted, Treatment CK (16% in soil moisture content and no biochar used), Treatment 1% BC(16% in soil moisture content and 1% biochar applied, w/w), Treatment 5% BC (16% in soil moisture content and 5% biochar applied), Treatment RSD (flooded, rice straw incorporated and no biochar used), Treatment RSD + 1% BC (RSD and 1% biochar applied) and Treatment RSD + 5% BC (RSD and 5% biochar applied). By determining the abundance of nitrifying functional genes (norB gene andnosZ gene encoding nitric oxide reductase and nitrous oxide reductase, respectively), activities of denitrifying microorganisms were characterized. Soil samples were collected from the treatments and incubated at 30 ºC in dark for 14 days,and N2O emission rate was measured during the incubation using the accumulative method. Besides, soil samples were also collected for analysis of inorganic nitrogen contents, soil pH and abundance of denitrifying functional genes. Each sampling had four replicates. Results show that RSD significantly lowered soil nitrate content, raising soil pH and retarded soil degradation, but the cumulative N2O emission from the RSD-treated soils was over 950 times as high as that from their non-RSD treated counterparts. Application of 5% Biochar reduced the N2O emission in degraded vegetable soil and its RSD process by 68.7% and 16.0%, respectively. Pearson correlation analysis reveals a negative relationship between N2O emission rate and soil pH in both degraded vegetable soil and its RSD process, and a positive relationship between N2O emission rate and soil ammonium content in RSD process. The abundance of norB and nosZ genes was also significantly changed after biochar application. Linear regression analysis shows that soil N2O emission was mainly related to nosZ gene abundance in degraded vegetable soil, but to norB gene abundance in RSD process. To sum up, the application of 5% biochar in degraded vegetable soil and its RSD process can elevate soil pH and alter abundances of the critical denitrifying functional genes, thus efficiently mitigating N2O emission. All the findings in this study may serve as experimental evidence for N2O mitigation in degraded vegetable soil, and also can be regarded as important indices for assessment of environmental effects of the remediation of degraded vegetable soil.
王 军,施 雨,李子媛,韩 成,谢祖彬,钟文辉.生物炭对退化蔬菜地土壤及其修复过程中N2O产排的影响[J].土壤学报,2016,53(3):713-723. DOI:10.11766/trxb201509170443 WANG Jun, SHI Yu, LI Ziyuan, HAN Cheng, XIE Zubin, ZHONG Wenhui. Effects of Biochar Application on N2O Emission in Degraded Vegetable Soil and in Remediation Process of the Soil[J]. Acta Pedologica Sinica,2016,53(3):713-723.复制