Trade-offs between wheat soil N₂O emissions and C sequestration under straw return, elevated CO₂ concentration, and...

Area of Science:

• Agricultural Science
• Environmental Science
• Climate Science

Background:

• Understanding the interplay between nitrous oxide (N2O) emissions, straw management, and climate change is crucial for wheat ecosystems.
• Future climate scenarios, including elevated carbon dioxide (CO2) and temperature, significantly influence agricultural greenhouse gas dynamics.

Purpose of the Study:

• To investigate the impact of straw return (incorporation and mulching) versus removal on N2O emissions, soil properties, and N-cycling genes under future climate conditions.
• To evaluate the net global warming potential (NGWP) and greenhouse gas intensity (GHGI) of different straw management practices.

Main Methods:

• Experimental manipulation of straw return (incorporation, mulching) and removal under ambient and elevated CO2 and temperature conditions.
• Measurement of N2O emissions, soil physicochemical properties, enzyme activities, and functional genes involved in nitrogen cycling.
• Calculation of NGWP and GHGI based on greenhouse gas emissions, crop yield, and soil organic carbon (C) sequestration.

Main Results:

• Elevated CO2 and temperature individually suppressed N2O emissions by 41-46%.
• Straw return significantly increased N2O emissions (31-109%) by enhancing soil C and N substrates and denitrifying gene abundance, with a greater impact than elevated CO2 or temperature.
• Straw return reduced NGWP and GHGI by increasing soil organic C sequestration and grain yield, with incorporation being more effective than mulching.

Conclusions:

• While straw return stimulates N2O emissions in wheat systems under future climates, it enhances grain yield and soil organic C sequestration more significantly.
• Straw return is a beneficial strategy for climate change mitigation in agriculture, particularly through straw incorporation.
• Management practices need to balance N2O mitigation with the benefits of soil carbon enhancement and yield increases.