Soil pH Determines Nitrogen Effects on Methane Emissions From Rice Paddies

Area of Science:

• Agricultural Science
• Environmental Science
• Soil Science

Background:

• Rice paddies contribute significantly to global methane (CH4) emissions, accounting for about 9% of human-induced sources.
• Nitrogen (N) fertilization practices in paddy soils have complex and often contradictory effects on CH4 emissions, with underlying mechanisms and global impact remaining unclear.
• This uncertainty complicates accurate global CH4 emission projections and the development of effective mitigation strategies.

Purpose of the Study:

• To elucidate the primary drivers of N fertilization's impact on CH4 emissions from rice paddies.
• To quantify the global contribution of N fertilization to CH4 emissions across rice paddy areas.
• To establish a predictive relationship between soil properties, N fertilization, and CH4 emissions.

Main Methods:

• Conducted a comprehensive meta-analysis integrating data from various field experiments.
• Performed targeted experiments to investigate the interactions between soil pH, N fertilization, and CH4 production.
• Utilized statistical modeling to quantify the impact of N fertilization on area-scaled and yield-scaled CH4 emissions globally.

Main Results:

• The effect of N fertilization on CH4 emissions from rice paddies is strongly correlated with soil pH.
• N fertilization most significantly enhances CH4 emissions in acidic soils, attributed to accelerated organic matter decomposition and increased methanogen activity.
• Global CH4 emissions from rice paddies are estimated to have increased by 52% (area-scaled) and 8.2% (yield-scaled) due to N fertilization.

Conclusions:

• Soil pH is a critical factor mediating the impact of N fertilization on rice paddy CH4 emissions.
• Alleviating soil acidification and implementing sound N management practices are essential for reducing greenhouse gas emissions from agriculture.
• This research provides a quantitative basis for refining global methane budgets and developing targeted mitigation strategies in rice cultivation.