Nitrous oxide emissions in nonflooding period from fallow paddy fields

Area of Science:

• Agricultural Science
• Environmental Science
• Soil Science

Background:

• Non-flooded, fallow paddy fields can be a source of nitrous oxide (N2O) emissions.
• Understanding N2O dynamics in these periods is crucial for mitigating greenhouse gas release.

Purpose of the Study:

• To investigate N2O emissions and dissolved N2O in leachate during the non-flooding period in fallow paddy fields.
• To determine the impact of soil cracking on N2O flux and leachate N2O concentrations.

Main Methods:

• Soil columns of three different textures (silty clay-loam and silty loam) were incubated in a greenhouse.
• Columns were initially supersaturated with water and then gradually dried.
• N2O emissions flux and dissolved N2O in leachate were measured during the incubation period.

Main Results:

• Soils that developed cracks (silty clay-loam) exhibited significantly higher N2O emissions (1,280.9 and 1,133.3 µg/(m²·h)) compared to non-cracked soil (silty loam; 426.3 µg/(m²·h)).
• Cracked soils showed two daily peaks in N2O emissions (14:00 and 2:00), while non-cracked soil had only one peak (2:00).
• Dissolved N2O concentrations in leachate were higher in non-cracked soil, suggesting preferential flow may not significantly impact dissolved N2O during cracking.

Conclusions:

• Fallow paddy fields pose a substantial risk for N2O emissions during non-flooding periods.
• Soil cracking is a key factor influencing the magnitude and diurnal patterns of N2O emissions.
• Supersaturated dissolved N2O in leachate represents a potential source for N2O emissions.