ARS | Publication request: Predicting long-term organic carbon dynamics in organically-amended soils using the CQESTR model

Submitted to: Journal of Soils and Sediments
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 14, 2011
Publication Date: April 8, 2012
Citation: Plaza, C., Gollany, H.T., Baldoni, G., Polo, A., Ciavatta, C. 2012. Predicting long-term organic carbon dynamics in organically-amended soils using the CQESTR model. Journal of Soils and Sediments. 12:486-493.

Interpretive Summary: The CQESTR model is a process-based carbon model, which uses readily measurable input parameter, was developed to simulate soil organic matter dynamics. The model has been validated successfully for North America, but needs to be tested in other geographic areas and soils types under diverse organic management systems. In this work, we evaluated the predictive performance of CQESTR to simulate long-term (34 years) organic carbon changes in a soil organic carbon-depleted European soil either unamended or amended with solid manure, liquid manure, or crop residue. Measured soil organic carbon declined over the study period in unamended soil, remained constant in the soil amended with crop residue, and increased with manure, especially with solid manure. The CQESTR model was shown to predict, with a reasonable degree of accuracy, the soil organic carbon dynamics in the soils examined. Measured and CQESTR predicted values were well correlated. Simulated values fell within the 95% confidence interval of the measured soil organic carbon, and predicted errors were mainly associated with data scattering. The CQESTR performance, however, could be improved by adding an additional parameter to differentiate between pre-decomposed organic amendments with varying degrees of stability.

Technical Abstract: A process-based soil C model “CQESTR” was developed to simulate soil organic carbon (SOC) dynamics. The model has been validated successfully for North America, but needs to be tested in other geographic areas. We evaluated the predictive performance of CQESTR in a long-term (34-yr) SOC-depleted European soil either unamended or amended with solid manure, liquid manure, or crop residue. Measured SOC declined over the study period in unamended soil, remained constant in the soil amended with crop residue, and increased with manure, especially with solid manure. The CQESTR model predicted the organic C dynamics, with a reasonable degree of accuracy. Linear regression analysis of measured and CQESTR predicted resulted in a correlation coefficient of 0.626 (P < 0.001) and a slope near 1. The mean squared deviation and root mean square error were relatively small. Simulated values fell within the 95% confidence interval of the measured SOC, and predicted errors were mainly associated with data scattering. The CQESTR performance, however, could be improved by adding an additional parameter to differentiate between pre-decomposed organic amendments with varying degrees of stability.