Simulating Soil Fertility Restoration Using the CAST Model

The CAST model was used to simulate soil fertility restoration due to soil organic carbon (SOC) depletion in cultivated Mediterranean soils using organic amendments (compost and manure) under different tilling practices. Two cropland fields (35 years of cultivation) in the Koiliaris CZO (Chania, Crete, Greece) were simulated to reach SOC at such levels that soil functions are maintained. Two soil function indicators were used to evaluate restoration of fertility: the SOC/silt+clay ratio with a threshold value of 4.5 and the water stable aggregate (WSA) fraction (>250 μm) to exceed 60% for the soil to be “agronomically valuable”. A mixture of 70% municipal solid waste compost to 30% manure was used as organic amendment and different tilling practices (light and intense tilling) were considered to investigate the fertility restoration design as well as the impact of tilling and organic amendments on soil structure.