Soil C sequestration potential of exogenous organic matter: an integrated laboratory and modelling approach

The main aim of this thesis was to combine laboratory data and soil C modelling to find a reliable procedure to evaluate soil C sequestration potential of exogenous organic matter (EOM) at site and national scale. For this purpose, the RothC soil C model was either modified by introducing specific EOM pools and calibrated by fitting respiratory curves from laboratory incubations of soils amended with contrasting EOMs and a procedure was devised for spatially explicit SOC modelling after EOM application. The main outputs of the research showed that the modified model is effective in simulating the respiration response of laboratory incubated amended soils. Long term (100 years) model simulations indicated that EOMs greatly differ for their soil C sequestration potential (range: 0.11-0.38 t C ha-1 y-1). The soil C sequestration potential of compost applied for 100 years to all Italian agricultural land corresponded to 4.6% of total annual GHG emissions for Italy. Spatial explicit modelling of amended soil indicated a high variability in the potential of SOC accumulation (range: 0.06-0.62 t C ha-1 y-1) and allowed areas with the largest potential for SOC storage to be identified, therefore suggesting ways for optimizing resources. Findings of the present study highlight the importance of laboratory data to enhance the capability of models to predict soil C sequestration potential of amended soils and assist decision makers to adopt management options favouring soil C accumulation of EOM.