N2O emissions have increased significantly over the last decades, with much of the increase being ascribed to the expansion in agricultural land. Agricultural water management has significant influence on N2O emissions, hence the investigation of N2O emissions and the underlying production mechanisms under different irrigation managements would provide insights for N2O emission reduction and rational water usage. Here, we used the stable isotope method to evaluate the N2O isotopic signatures and the site preference, to clarify the N2O emission dynamics and the N2O source partitioning under different irrigation managements. We applied a furrow irrigation system and a drip irrigation system to maintain two different soil water conditions, allowance of dry-wet cycles and relatively stable water conditions, respectively. We found that the N2O emission was significantly decreased under drip irrigation compared to furrow irrigation with cumulated N2O flux of 526.3 mg m-2 and 571.0 mg m-2, respectively. In general, furrow irrigation with its dry-wet alternations promoted N2O emissions, while drip irrigation created a relatively stable environment that reduced N2O emissions. The intramolecular 15N isotopic composition of N2O was used to partition the relative contribution of denitrification and nitrification. Nitrification dominated the processes driving N2O production under both treatments, nearly accounting for 76% up to 100% during the initial N2O peaks. Effective measure for mitigating N2O emissions from the investigated vegetable field could be obtained by replacing the traditional furrow irrigation with drip irrigation.
Keywords: Denitrification; Irrigation; N(2)O emissions; Nitrification; Stable isotopes; Water-filled pore space (WFPS).
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