Simulating changes of organic carbon content in soil following tillage intensity and fertilizer N rate reduction

Economic, environmental, and societal benefits are expected from good practices of soil carbon (C) management (Kimble et al., 2007). However, new tools are required for national and local policymakers to accurately estimate the effects of different agricultural management practices on greenhouse gas emissions and removals. The2006 IPCC Guidelines for National Greenhouse Gas Inventories(IPCC, 2006), which provide methodologies for estimating national inventories of anthropogenic emissions and removals of greenhouse gases, together with theGood Practice Guidance for Land Use, Land-Use Change and Forestry(IPCC, 2003), provide internationally agreed methodologies for this purpose, and include the possibility of using simulation models ashigher ordermethods for gas inventories in the Agriculture, Forestry and Other Land Use (AFOLU) sector. According to theIPCC Guidelines, models should undergo quality-checks, audits, and validations and be thoroughly documented.Tillage intensity reduction is known to increase the soil organic C sink potential (Paustian et al., 1995; Al-Kaisi and Yin, 2005), whereas the effect on C sink of supplying soil with N fertilizer is less understood (Khan et al., 2007). The main objective of this study was to estimate the change of organic C content in the cultivated soil layer as a function of change in tillage intensity, in interaction with different fertilizer N rates. The Daisy model was used for this purpose, in view of its possible future application at regional scale for the estimation of AFOLU-related greenhouse gas emissions.