Optimizing rice yields while minimizing yield-scaled global warming potential.

Area of Science:

• Agricultural Science
• Environmental Science
• Climate Change Research

Background:

• Growing global food demand necessitates increased agricultural productivity with reduced environmental impact.
• Greenhouse gas (GHG) emissions from agriculture are increasingly assessed on a yield-scaled basis to account for crop productivity.
• Rice production is a major contributor to agricultural GHG emissions, particularly methane (CH4) and nitrous oxide (N2O).

Purpose of the Study:

• To test the hypothesis that yield-scaled global warming potential (GWP) is minimized at optimal nitrogen (N) fertilizer rates that maximize rice yields.
• To evaluate the impact of N fertilizer application on CH4 and N2O emissions and their contribution to GWP in rice systems.
• To compare GHG emission scaling in rice systems with aerobic cropping systems.

Main Methods:

• Compiled field data on CH4 and N2O emissions from rice production systems.
• Calculated yield N surplus to estimate N application rates relative to optimal N rates.
• Applied linear and nonlinear mixed-effects models to assess relationships between yield N surplus and GHG emissions.

Main Results:

• Rice yields increased with N surplus up to optimal N rates.
• N2O emissions and yield-scaled N2O emissions increased exponentially at N rates above optimal.
• CH4 emissions were unaffected by N inputs, leading to decreased yield-scaled CH4 emissions with N addition.
• Overall yield-scaled GWP was minimized at optimal N rates, showing a 21% reduction compared to unfertilized treatments.

Conclusions:

• Optimal N application rates in rice production minimize yield-scaled GWP while maximizing yields.
• This strategy supports sustainable intensification by balancing agricultural productivity and climate change mitigation.
• Improvements in nitrogen use efficiency can further reduce yield-scaled GWP in rice systems.