# Hotspots of N2O accumulation in the soil profile of alternate wetting and drying paddy fields

## TL;DR

This study identifies the top 20 cm of soil as a hotspot for nitrous oxide accumulation in paddy fields using alternate wetting and drying irrigation.

## Contribution

The study reveals that the 10–20 cm soil layer is the main driver of N2O emissions in alternate wetting and drying paddy fields.

## Key findings

- N2O concentrations in 0–30 cm soil profiles increased by 19.6–79.0% under IAWD compared to continuous flooding.
- The 10–20 cm soil layer was identified as the dominant hotspot for N2O accumulation and emissions.
- N2O accumulation in the 0–20 cm soil profile is critical for targeted mitigation strategies in IAWD paddy fields.

## Abstract

Alternate wetting and drying irrigation (IAWD) is a promising practice for water conservation and climate mitigation, yet it inadvertently stimulates substantial nitrous oxide (N2O) emissions. While previous research has largely focused on surface N2O fluxes, the processes governing N2O accumulation and emission across the soil profile–surface continuum remain poorly understood.

Here, we present a comprehensive dataset from a lysimeter study on paddy fields under IAWD and continuously flooded irrigation (ICF), integrating measurements of soil N2O concentrations (0–50 cm depth, at 10-cm intervals) and concurrent surface fluxes.

The results showed that N2O predominantly accumulated in 0–20 cm soilprofiles during the tiller fertilizer period (TF) and panicle fertilizer period (PF) regardless of the irrigation regimes. Compared to ICF, IAWD significantly increased the N2O concentrations in 0–30 cm soil profiles by 19.6–49.3% and 60.0–79.0% during the TF and PF, respectively. Partial least-squares path model further identified the 10–20 cm layer as the dominant hotspot, exerting the strongest direct control on surface N2O emissions.

Altogether, 0–20 cm soil profiles are the hotspots for N2O accumulation in IAWD paddy fields, and the N2O accumulated in 10-20 cm soil profile dominates the N2O emissions. These findings contribute to the adoption of straightforward and targeted N2O mitigation strategies in IAWD paddy fields.