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Title:   Author  item
                                            Wienhold, Brianitem
                                            Schmer, Martyitem
                                            Jin, Virginiaitem
                                            VARVEL, GARY - Retired ARS Employeeitem
                                            Gollany, Hero
  Submitted to: BioEnergy Research
                                    Publication Type: Peer Reviewed Journal
                                    Publication Acceptance Date: 6/30/2015
                                    Publication  Date: 7/23/2015
                                    Citation: Wienhold, B.J., Schmer, M.R., Jin, V.L., Varvel, G.E., Gollany, H.T. 2015. CQESTR simulated changes in soil organic carbon under residue management practices in continuous corn systems. BioEnergy Research. doi:10.1007/S12155-015-9654-6.Interpretive Summary: Crop residues are being used as livestock feed and may be used for biofuel production in the future. Removal of residue from fields has the potential to negatively affect soil quality. These negative effects may be difficult to measure as they often occur slowly over long time periods. Models may help with assessing management effects on soils but they must be validated using available long-term data. CQESTR is a model that uses management practices and site weather to estimate changes in soil carbon. We compared CQESTR estimated changes in soil carbon to measured changes in soil carbon in two studies in eastern NE. These studies included rainfed vs. irrigated continuous corn under various tillage, N fertilizer rates, and residue removal rates. Changes in soil carbon estimated with the model agreed very well with changes measured in these studies after ten years.
                                Technical Abstract: Soil organic carbon (SOC) is an important soil property and strongly influenced by management. Changes in SOC stocks are difficult to measure through direct sampling, requiring both long time periods and intensive sampling to detect small changes in the large, highly variable pool. Models have the potential to predict management-induced changes in SOC stocks but require long-term data sets for validation. CQESTR is a processed-based C model that uses site weather, management, and crop data to estimate changes in SOC stocks. Crop residue removal for livestock feed or future biofuel feedstock use is a current management practice potentially affecting SOC stocks.  Simulated changes in SOC using CQESTR were compared to measured SOC changes over 10 years for two contrasting residue removal studies in eastern NE. The rainfed study compared SOC changes in no-tillage continuous corn grown under two N fertilizer rates (120 or 180 kg N ha-1) and two residue removal rates (0 or 50%). The irrigated study compared SOC changes in continuous corn grown under no-tillage or disk tillage and three residue removal rates (0, 35 or 70%). After 10 years under these management scenarios, CQESTR-estimated SOC stocks agreed well with measured SOC stocks at both sites (r2 = 0.93 at the rainfed site, r2 = 0.82 at the irrigated site). These results are consistent with other CQESTR validation studies and demonstrate that this process-based model can be a suitable tool for supporting current management and long-term planning decisions.


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