Nitrifier denitrification can contribute to N2O emissions substantially in wet agricultural soil

Abstract

Nitrifier denitrification (ND) is recognized as an important pathway for N₂O production in agricultural soils, yet its contributions under different moisture contents are poorly quantified. Using an enriched dual isotope (¹⁵N − ¹⁸O) approach, we estimated N₂O production from ND across eight moisture levels (40–120% water-filled pore space, WFPS) in a typical agricultural soil from the North China Plain. Total N₂O flux began to increase when WFPS exceeded 70%, peaking at 100% WFPS, indicating substantial N₂O emission potential in wet soils. In contrast, the N₂O production from ND increased gradually from 40–70% WFPS, rose sharply from 70–90% WFPS, stabilized between 90–100% WFPS, and declined rapidly from 100–120% WFPS. ND contributed approximately 20%, 80%, and 30% of N₂O emissions under low (40–50% WFPS), intermediate (60–70% WFPS), and high (80–120% WFPS) moisture conditions, respectively. Future contributions from ND may increase as irrigation and extreme rainfall events become more frequent under changing climates.