Effects of Nitrogen Application on Soil Nitrification and Denitrification Rates and N۲O Emissions in Greenhouse

Nitrous oxide (N۲O) has significant impact on global warming and leads to the depletion of ozone in the stratosphere. Agricultural soil is regarded as a major source of N۲O emissions. In recent years, greenhouse grown vegetables have rapidly developed in China. Although excessive fertilizer application in greenhouse vegetable production can result in increased N۲O emissions, research data on such emissions from greenhouse vegetables, such as cucumber, remains limited. In this study, four nitrogen (N) fertilizer treatments including ۱,۲۰۰ (N۱۲۰۰, traditional N amount), ۹۰۰ (N۹۰۰), and ۶۰۰ kg N ha-۱ (N۶۰۰) and the control (N۰) were carried out on cucumber in a greenhouse in the North China Plain. Results showed that N۲O emissions mainly occurred in the first five days after topdressing, and accounted for ۷۵.۸%-۹۵.۲% of total N۲O emissions produced in the whole interval (۱۰ days). Significant exponential correlations were observed between N۲O flux and nitrification or denitrification rates (P< ۰.۰۱). The results also indicated that nitrification dominated and played a more important role in N۲O emissions than denitrification under the irrigation conditions of the study (water-filled pore spacewas ۴۰.۰ to ۶۶.۶%). Cumulative N۲O emissions were ۰.۴۸-۵.۰۱ kg N ha-۱ in the cucumber growing season, accounting for ۰.۲۸-۰.۳۸% of nitrogen input. Compared to N۱۲۰۰, treatment N۶۰۰ significantly reduced the rate of N۲O emissions by ۵۳.۴%, and also maintained cucumber yield. Based on this study, ۵۰% of the traditional N fertilizer rate (N۶۰۰) was considered sustainable for greenhouse cucumber production in the North China Plain.

Keywords:

Cucumber , Environmental factor , Nitrogen fertilizer , N۲O flux. Soil NO۳-N