New Modeling Approach to Describe and Predict Carbon Sequestration Dynamics in Agricultural Soils

The contribution of agro-ecosystems to carbon sequestration in the form of soil organic matter (SOM) is increasingly considered as a mitigating factor for climate change. The ecosystem carbon storage depends on the balance between C inputs and outflows due to SOM breakdown. SOM decomposition has been reported as mostly affected by temperature and water availability, at global and regional scale, and by C quality at local scale, where climate can be considered relatively uniform. In this work, a new model of SOM decomposition is presented. The SOMDY model is based on an advanced description of SOM chemical quality by 13C-CPMAS NMR instead of traditional C/N ratio. The model includes also the effects of physical aggregation of organic matter. SOMDY was calibrated on CO2 emission data from extensive field experimental measurements. The simulation results showed the model capability to predict SOM changes during decomposition processes, including the effects of addition of organic amendments (e.g. compost applications, crop residual burial), as well as the impact of different tillage practices on the physical structure of soil aggregation.