Modelling crop management effects on soil organic C stocks and pools dynamics using CENTURY

Abstract

International audienceSoils constitute the major reservoir of organic carbon storing around 2500 Pg C in the top two meters which correspond to approximately more than three times the amount of C stored in the atmosphere (Jobbágy and Jackson, 2000; Tarnocai et al., 2009) and six times the amount of C stored in terrestrial vegetation (Prentice et al., 2001). Consequently, small changes in soil organic carbon (SOC) stocks will greatly affect the global ecosystem carbon cycling and potentially the global climate (Davidson and Janssens, 2006; Heimann and Reichstein, 2008). Beside its importance in the global terrestrial C cycle, SOC is also a key component for sustainable productivity in agro-ecosystems. Improving agricultural practices represents a win-win strategy that has the potential to enhance soil fertility and sequester C (Lal, 2004). However, there still uncertainties about agricultural practices impacts on SOC stocks dynamics and controversial and contradictory results in the literature are common (Luo et al., 2010; Virto et al., 2011). These uncertainties are mainly attributed to the lack of continuous SOC monitoring in long-term experiments, the diversity of climatic conditions (Powlson et al., 2014), and the antagonistic effects of some practices such as fertilization or irrigation. Modeling represents a valuable tool to simulate the spatial and temporal SOC stocks dynamics in response to the fast changes in policies, agriculture practices and their complex interaction with current and projected future climatic conditions. The main objectives of this work were: to analyze the interaction between crop management and climatic conditions in the long-term on SOC dynamics as simulated by theCentury model (Parton et al., 1987) across France and to quantify GHG emissions and SOC stocks at different scales in order to apply the Tier 3 methodology for the GHG inventories. We examined more than 20 sites with different Long-term experiments, ranging from 10 to 40 years, across the France. Different agricultural practices were studied such as tillage treatments, crop rotation, organic amendment, mineral fertilization, etc. We used the well-validated Century model which has been widely used all over the world to simulate SOC dynamics in agricultural systems. Model parameters calibration through inverse modeling using PEST (Doherty, 2010) was applied to estimate some of the parameter values. First results showed that the model gave satisfactory results for the SOC stocks dynamics over the layer 0-20 cm. Model parameters calibration improved the fit for to crop productivity and SOC. An important result emerged from this work emphasis that agricultural practices that maximize C input are more effective strategies for SOC sequestration than those that limit SOC mineralization. Further results will be given in the poster