Substituting Synthetic Fertilizers with Organic Options May Have Large Climate Benefits

Strategic Insights -

A new report from a team of researchers at Peking University reveals that substituting synthetic fertilizers with solid organic fertilizers can contribute to mitigating climate change by increasing soil organic carbon stocks. However, the long-term benefits of this approach are not yet fully understood, and more research is needed to determine the net climate benefits of organic substitution. The study, which was supported by the Peking University Boya Postdoctoral projects, Agence Nationale de la Recherche (ANR), and the European project MRV4SOC, suggests that organic substitution can have a significant impact on reducing greenhouse gas emissions in China.

Key Takeaways:

  • The study found that organic substitution can increase soil organic carbon stocks by 4 Mg carbon dioxide equivalent (CO2-eq) ha-1 yr-1 on dryland soils.
  • However, organic substitution on paddy soils has limited net climate benefits due to increased methane emissions that offset the annual soil carbon benefits.
  • The net climate benefits of organic substitution are mostly determined by the duration of the substitution (-25% contributions), with limited long-term benefits.
  • Optimal substitution ratios of organic N and types of organic fertilizers can improve the long-term climate benefits.
  • The study estimates that organic substitution has the technical potential to shift China's croplands from a net carbon source of -300 Tg CO2-eq yr-1 to a small sink of 6 Tg CO2-eq yr-1, with a reduction potential of 2-3% of total national emissions on a 20-year time span.
  • Over 80% of the mitigation potential lies in arable lands with neutral to alkaline pH, low soil organic carbon, and temperate climate.

Statistics:

  • 1666 field paired observations were used in the meta-analysis.
  • 4 Mg CO2-equivalent ha-1 yr-1 is the amount of soil organic carbon increased by organic substitution on dryland soils.
  • 6 Tg CO2-eq yr-1 is the estimated amount of carbon emissions reduced by organic substitution in China's croplands.
  • -300 Tg CO2-eq yr-1 is the current net carbon source of China's croplands.
  • 20-year time span is the period over which the reduction potential of 2-3% of total national emissions was calculated.
  • 80% of the mitigation potential lies in arable lands with specific pH, soil organic carbon, and climate conditions.

Sources:

  • VerticalNews
  • China Weekly News
  • Journal of Cleaner Production, 2025;525
  • A Meta-analysis Reveals Large Potential of Substituting Synthetic Nitrogen Fertilizer With Solid Organic Fertilizer for Climate Mitigation In China
  • Peking University Boya Postdoctoral projects
  • Agence Nationale de la Recherche (ANR)
  • European project MRV4SOC
  • Feng Zhou, Peking University, Inst Carbon Neutral, College of Urban and Environmental Sciences, Laboratory for Earth Surface Processes, Beijing, People's Republic of China
  • Shuaixiang Zhao, Susanne Schmidt, Philippe Ciais, Bertrand Guenet, Benoit Gabrielle, Pete Smith, Yunting Fang, Xiaoyuan Yan, and Weifeng Zhang.