土壤学报2019，Vol.56Issue(1)：114-123,10.DOI:10.11766/trxb201803120102
碳源和氧对设施菜田土壤N2O排放的影响
Effects of Oxygen Levels and Carbon Inputes on N2O Emission in Greenhouse Vegetable Soil
摘要
Abstract
[Objective] In order to explore effects of oxygen level (0％, 1％, 3％, 10％ and 21％) and carbon input on major sources of N2 O emission in greenhouse vegetable soil, an on-line robotized monitoring and incubation system was used to automatically monitor real-time dynamics of O2, N2 O and N2 in greenhouse vegetable soil after a crop of tomato was harvested. In addition, dicyandiamide (DCD) , a kind of nitrification inhibitor, was added to investigate contribution of nitrification to N2 O emission from the soil relative to carbon source and oxygen level.[Method] A certain amount of soil sample collected from a vegetable field under greenhouse after a crop of tomato was harvested, was washed with deionized water and divided into two groups, labeled as T1 and T2, separately. T2 was spiked with glutamate, whereas T1 was not. NH4 NO3 was added as nitrogen source for both groups. Then the pretreated soil samples were put into 120 mL vials, 10.0 g in dry soil weight in each. Deionized water or solution containing NH4 NO3, C.H8 NO.Na·H2 O or DCD was sprayed onto the soil surface to adjust moisture content of the soil up to 250 g·kg-1 in line with the requirement of the treatment, T1 or T2. Then the soils in the sealed vials were placed in a thermostatic (20℃) waterbath trough for incubation. Concentrations of O2, N2 O, N2 and CO2 in the headspace of a vial were monitored online at intervals of 6 h, and pure O2 was supplemented with a hermetic syringe in the light of the monitoring results of the gases in the headspace to maintain an approximately constant oxygen concentration (1％, 3％, 10％ or 21％ (v/v)) in the sealed vials. [Result]Results show that N2 O emission declined exponentially with rising soil oxygen partial pressure (OPP) (R2=0.82, P＜0.001) .It peaked when OPP was 0％ or 1％, and fell below 30％ of the peak when OPP got equal to or higher than3％. Addition of available carbon into the vial reduced N2 O and N2 production in the soil under aerobic conditions, while significantly increasing the contribution of the process of heterotrophic denitrification in the soil to N2 O emission under near-anaerobic conditions (P＜0.01) , which suggests that this kind of soil is highly capable of triggering heterotrophic denitrification, and anaerobicity and near-anaerobicity is more favorable to N2 O emission. Compared with Group T1, Group T2 was 64.4％ and 88.8％ lower in N2 O emission, 23.4％ and 18.6％ lower in N2 emission, and 14.5％ and 62.3％ lower in N2 O/ (N2 O+N2) index (IN2 O) , respectively, when OPP was 1％ and 3％ and no carbon supplemented. However, when carbon was supplemented, the two groups did not vary much in N2 O and N2 emissions and IN2 O, which suggests that strong nitrification occurs in the soil with no carbon supplemented and N2 O comes mainly from heterotrophic denitrification process (HD) under aerobic conditions in the soil with sufficint carbon supply.DCD would lower the accumulation of NO2-, a substrate of nitrification-coupled denitrification (NCD) , which is considered to be an important contributor to N2 O emission under aerobic conditions; nevertheless, the process of NCD is still a heterotrophic one in nature. That is to say, DCD would reduce N2 O emission from nitrification processes, and from heterotrophic denitrification processes, too. With OPP rising from1％ to 3％, N2 O emission from nitrifier-induced denitrification (ND) increased from 17.2％ to 42.6％, however, the contribution of ND to N2 O emission in the vegetable soil was still quite low due to the drastic reduction in total N2 O emission. Moreover, the commonly used dual isotopic labeling method would lead to overestimation of the contribution of ND to N2 O emission because this method may rule partial NCD or HD processes into ND. As the soil in this study was quite high in pH and remained almost unchanged in nitrate content after the treatment with DCD, simultaneous heterotrophic nitrification-denitrification processes might be very weak. [Conclusion]Soil N2 O emission mainly occurs under anaerobic and near-anaerobic conditions (OPP=1％) . Heterotrophic denitrifiers make the biggest direct contribution to soil N2 O emissions, especially when carbon sources are abundant. NO2-is an important substrate of the process of nitrificationcoupled denitrification.关键词
氧分压/碳源/N2O/与硝化相耦合的反硝化/异养反硝化/硝化细菌反硝化Key words
Oxygen partial pressure (OPP)/Carbon source/Nitrious oxide (N2O)/Nitrification-coupled denitrification (NCD)/Heterotrophic denitrification (HD)/Nitrifier-denitrification (ND)分类
资源环境引用本文复制引用
陈吉吉,王乙然,曹文超,宋贺,王敬国..碳源和氧对设施菜田土壤N2O排放的影响[J].土壤学报,2019,56(1):114-123,10.基金项目
国家自然科学基金项目(41230856)资助 （41230856）
Supported by the National Natural Science Foundation of China( No.41230856) （ No.41230856）
