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Impact of root exudates on long-term soil carbon sequestration in agroecosystems

Secondary Supervisor(s): Dr Andrew Beacham

University of Registration: Harper Adams University

BBSRC Research Themes:

• Sustainable Agriculture and Food (Plant and Crop Science)
• Understanding the Rules of Life (Plant Science,Soil Science)

Project Outline

In recent times, regenerative agriculture (RA) especially minimising mechanical soil disturbance, increasing plant diversity and maintaining living roots in soils, is being promoted to address the negative impacts of conventional agriculture. One key mechanism through which the transition to RA will impact climate change is by changing the amount and composition of root exudates. These are carbon-rich compounds such as sugars and organic acids secreted by plant roots and play a critical role in regulating soil organic carbon (SOC) stabilization which is important for climate change mitigation. However, the long-term contribution of root exudates to stable carbon pools in managed agricultural systems remains poorly quantified.

The aim of the study is to investigate how root exudates influence the stabilization of SOC in agroecosystems. The findings will support sustainable land use and climate change mitigation policies by providing a mechanistic basis for root zone-focused interventions. Specific objectives are to:

1. Characterize root exudate profiles across major crop species and management systems (e.g., cover crops, tillage);

2. Trace the fate of exudate-derived carbon into labile and stable SOC pools;

3. Evaluate management strategies that enhance exudate-mediated carbon stabilization while minimizing carbon loss.

Existing well-replicated field crop and grass trials involving different plant species and management strategies will be used to achieve the objectives of the study. Exudates will be collected in-situ and profiled using liquid chromatography - mass spectrometry. Selected plant species will be labelled using stable isotopes

e.g. ¹³CO₂ to track carbon flow from root exudates into the particulate organic matter and mineral-associated organic matter soil fractions which represent the labile and stable carbon pools. Incorporated ¹³C, and CO2 and CH4 emissions will be quantified using isotope-ratio mass spectrometry and static gas chamber techniques.