Century simulated organic carbon content in soils of south central Chile with diverse ratios of 1500 kPa water to measured clay

Modeling of the content of soil organic carbon (SOC) is necessary in order to assess whether different land uses are sustainable over the long term, and to evaluate potential changes of carbon storage in soils. In this study, the Century model was used to estimate SOC in volcanic and non volcanic soils of the VIII Region of Chile, and compared with actual SOC of the official Series descriptions. The predicted values were not significantly different from measured SOC of the Entisol, Inceptisol, Mollisol, Alfisol, and Ultisol soil Orders, but were significantly lower for Andisol soils probably because of the presence of additional clay that was not measured in particle size analysis. The respective mean values of Century predicted and actual SOC (g m−2) were 2709 and 3801 for the Entisol soils (11); 5507 and 4940 for Inceptisol soils (24); 4556 and 5263 for Mollisol soils (24); 5015 and 5595 for Alfisol soils (15); 9706 and 6533 for Ultisol soils (6); and 5502 and 9081 for Andisol soils (13). The Century model also underestimated SOC in soils with increasing ratios (>1.2) of 1500 kPa water to measured clay at 50 cm soil depth, an indicator of isotic (volcaniclastic) mineralogy that likewise is associated with additional unmeasured clay in soil. Consequently, in regions with volcanic and non volcanic parent materials across the landscape the ratio can serve as an indicator of soils that have elevated values of SOC relative to the measured clay and subsequently require parameter adjustments, such as using the % calculated clay, for model calibration.