Year-to-year climate variability affects methane emission from paddy fields under irrigated conditions

Area of Science:

• Agricultural Science
• Environmental Science
• Soil Science

Background:

• Methane (CH4) emissions from rice paddies are a significant source of greenhouse gases.
• Climate change, characterized by rising temperatures and altered precipitation patterns, can influence CH4 emissions.
• Agricultural practices, including fertilization and straw management, play a crucial role in regulating CH4 emissions and crop productivity.

Purpose of the Study:

• To investigate the impact of different fertilizer treatments (conventional chemical fertilizers (CF), CF with wheat straw (CF-WS), slow-release urea fertilizer with wheat straw (SCF-WS), and no fertilizer (Non-F)) on methane emissions, rice grain yield, and straw biomass.
• To assess these effects across three growing seasons, including a notably warm-and-dry season (2013) and two normal seasons (2014, 2015).
• To determine the relationship between environmental conditions, agricultural practices, and greenhouse gas emissions in rice cultivation.

Main Methods:

• A three-year field experiment was conducted in the Yangtze River delta, China.
• Four distinct soil management treatments were applied: CF, CF-WS, SCF-WS, and Non-F.
• Measurements included seasonal total methane emissions, rice grain yield, and straw biomass, alongside monitoring of air temperature and precipitation.

Main Results:

• Seasonal methane emissions were substantially higher (58-294%) in the warm-and-dry season (2013) compared to normal seasons (2014, 2015), indicating temperature's significant role.
• Treatments involving wheat straw incorporation (CF-WS and SCF-WS) increased methane emissions before mid-season drainage and overall, particularly in the warmer season.
• The combination of slow-release urea fertilizer and wheat straw (SCF-WS) significantly enhanced above-ground biomass yield and nitrogen use efficiency in both normal and warm-and-dry conditions, despite variable grain yields in the dry year.

Conclusions:

• Elevated air temperatures are a primary driver of increased methane emissions from paddy fields, especially during mid-to-late growth stages.
• Incorporating wheat straw, particularly with slow-release urea fertilizer, offers a promising strategy to improve crop biomass and nitrogen utilization efficiency.
• Sustainable agricultural practices that integrate organic matter and optimized fertilization are crucial for mitigating greenhouse gas emissions while maintaining crop productivity under changing climatic conditions.