TRUESOIL Project: Understanding Trade-offs and Dynamic Interactions between SOC Stocks and GHG Emissions for Climate Smart Agrisoil Management

According to the Paris Agreement 2015, increased carbon sequestration by soils is a vital option for climate change mitigation and, simultaneously, improves soil health and food security. Agricultural soils are globally depleted in soil organic carbon and, therefore, exhibit a high potential for carbon sequestration. Various agroecological practices aim to increase or maintain soil organic carbon through increasing carbon inputs in the soil (e.g., amendments, plant residues, cover crops) and/or through reducing carbon losses (e.g., reduced or no tillage, adapted grazing). However, these practices have the potential to increase greenhouse gas emissions, which limits their effectiveness in terms of climate change mitigation.

The EJP-SOIL project TRUESOIL (2022-2025) studies trade-offs between agricultural management practices aiming at increasing carbon sequestration and reducing greenhouse gas emissions from agroecosystems across crops, soil properties and climates. TRUESOIL investigates biotic and abiotic drivers of soil organic carbon dynamics and greenhouse gas emissions under field conditions in experimental croplands and grasslands in 13 countries and five continents, covering broad environmental and pedogenic gradients. Further, TRUESOIL investigates the impact of experimental droughts under rainout shelters on crop yields, soil organic carbon pools and greenhouse gas emissions. The project will improve the mechanistic understanding of soil organic matter and greenhouse gas interactions and predict trade-offs between management-induced soil organic carbon changes and greenhouse gas emissions under future climatic conditions. Finally, laboratory incubations will address the role of microbial community composition as shaped by agricultural management in soil organic matter stabilization and nutrients turnover.

TRUESOIL moves beyond bulk soil organic carbon stocks and studies the operational carbon pools of particulate and mineral-associated organic matter. While multiple greenhouse gases are targeted, a focus is given on N₂O due to its high warming potential and its relative uncertainty in flux calculations compared to CH₄ and CO₂ gases. Spanning from boreal to tropical climates, TRUESOIL sites cover a mean annual temperature range from 6 to 27°C and a precipitation range from 300 to 1150 mm. Similarly, soil organic carbon concentrations ranged from 1% to 10% with some sites greatly depleted in soil organic carbon, while others not and without signs of carbon saturation. Based on its wide geographical coverage, the TRUESOIL project will provide recommendations on management measures relevant to multiple stakeholders, from farmers to policy makers.