Denitrification contributes to N₂O emission in paddy soils

Area of Science:

• Environmental Microbiology
• Biogeochemistry
• Soil Science

Background:

• Denitrification is crucial for nitrogen cycling and greenhouse gas emissions.
• Paddy soils are significant contributors to denitrification.
• The mechanisms of nitrous oxide (N₂O) emission from paddy soil denitrification remain unclear.

Purpose of the Study:

• Investigate the N₂O emission potential from paddy soil denitrification.
• Analyze the enzymatic activities related to N₂O production and reduction.
• Determine the microbial community composition and gene abundance involved in denitrification.

Main Methods:

• Utilized the ¹⁵N isotope tracer technique.
• Conducted slurry incubation experiments.
• Measured enzymatic activities, quantitative polymerase chain reaction (qPCR), and metagenomic sequencing.

Main Results:

• Identified average potential N₂O emission rates of 0.51 ± 0.20 μmol⋅N⋅kg^-1⋅h^-1 (2.16 ± 0.85% of denitrification).
• Observed higher N₂O production enzymatic activity (2.77–8.94 times) than reduction activity, indicating an imbalance.
• Metagenomic analysis revealed specific microbial phyla, like Gammaproteobacteria, contributing to N₂O emission.

Conclusions:

• Paddy soil denitrification exhibits an imbalance favoring N₂O production, leading to significant emissions.
• Denitrification is a modular process involving diverse microbial communities.
• Estimated annual N₂O emissions from surface paddy soils are 13.67 ± 5.44 g N₂O⋅m^-2⋅yr^-1.