Simulation study of soil organic matter dynamics as affected by land use and agricultural practices in semiarid Cordoba, Argentina

Soil carbon sequestration has been recognized as an effective, low-cost technology to mitigate climate change. Simulation models, alone or in combination with soil sampling and other techniques, can help monitor changes in soil carbon levels as affected by climate, soil, and management conditions. The objective of this paper is to test the ability of the Environmental Policy Integrated Climate (EPIC) model to simulate total organic carbon (TOC) dynamics in soils of the central region of the Province of Cordoba (Argentina) and evaluate, through modeling, the capacity of Cordoba's agricultural soils to act as sources or sinks of atmospheric CO2. We tested EPIC against measurements made in a spatially distributed 40-year chronosequence of a temperate shrubland forest transitioning to agricultural use with conventional practices and in two long-term tillage (moldboard plow, chisel plow, and no till) and crop rotation (maize [Zea mays L.]-soybean [Glycine max L. Merr.]) field studies. Overall, the EPIC model demonstrated a good capability for simulating TOC dynamics. In the chronosequence, the TOC lost during 40 years of cultivation after deforestation was calculated at 38.4 Mg ha(-1) while that simulated by the model was 44.1 Mg ha(-1). These values represented losses of 44% and 45% of the original TOC content, respectively. In the two long-term field experiments, the TOC simulated over the entire depth was close to the observed values and reflected the trends of the various treatments. For the most common conditions of croplands in Cordoba, crops grown in rotation with conservation tillage, particularly no till, would make soils act as sinks of atmospheric CO2. (C) 2008 Elsevier B.V. All rights reserved.