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Nitrous oxide (N₂O) 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 N₂O emissions. In recent years, greenhouse grown vegetables have rapidly developed in China. Although excessive fertilizer application in greenhouse vegetable production can result in increased N₂O emissions, research data on such emissions from greenhouse vegetables, such as cucumber, remains limited. In this study, four nitrogen (N) fertilizer treatments including 1,200 (N₁₂₀₀, traditional N amount), 900 (N₉₀₀), and 600 kg N ha^-1 (N₆₀₀) and the control (N₀) were carried out on cucumber in a greenhouse in the North China Plain. Results showed that N₂O emissions mainly occurred in the first five days after topdressing, and accounted for 75.8%-95.2% of total N₂O emissions produced in the whole interval (10 days). Significant exponential correlations were observed between N₂O flux and nitrification or denitrification rates (P< 0.01). The results also indicated that nitrification dominated and played a more important role in N₂O emissions than denitrification under the irrigation conditions of the study (water-filled pore spacewas 40.0 to 66.6%). Cumulative N₂O emissions were 0.48-5.01 kg N ha^-1 in the cucumber growing season, accounting for 0.28-0.38% of nitrogen input. Compared to N₁₂₀₀, treatment N₆₀₀ significantly reduced the rate of N₂O emissions by 53.4%, and also maintained cucumber yield. Based on this study, 50% of the traditional N fertilizer rate (N₆₀₀) was considered sustainable for greenhouse cucumber production in the North China Plain.

Keywords: Cucumber, Environmental factor, Nitrogen fertilizer, N2O flux. Soil NO3-N

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