Comparison of evapotranspiration and biomass simulation in winter wheat under conventional and conservation tillage systems using APEX model

Authors: TADESSE, HAILE - Environmental Protection Agency (EPA); Moriasi, Daniel; Gowda, Prasanna; Wagle, Pradeep; Starks, Patrick; STEINER, JEAN - Kansas State University; TALEBIZADEH, MANSOUR - Non ARS Employee; Neel, James; Nelson, Amanda

Submitted to: Ecohydrology & Hydrobiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/12/2020
Publication Date: 8/20/2020
Citation: Tadesse, H.K., Moriasi, D.N., Gowda, P.H., Wagle, P., Starks, P.J., Steiner, J.L., Talebizadeh, M., Neel, J.P., Nelson, A.M. 2020. Comparison of evapotranspiration and biomass simulation in winter wheat under conventional and conservation tillage systems using APEX model. Ecohydrology & Hydrobiology. https://doi.org/10.1016/j.ecohyd.2020.08.003.
DOI: https://doi.org/10.1016/j.ecohyd.2020.08.003

Interpretive Summary: The Agricultural Policy/Environmental eXtender (APEX) is one of the hydrologic and water quality models used to evaluate the effect of agricultural production management practices on the environment. Tillage practices used affect agricultural production, soil erosion, and evapotranspiration (ET), which is a major component of the water cycle. However, there is limited reported research related to the impact of tillage practices on parameterization and performance of APEX to simulate ET. Therefore, this study sought to 1) determine model parameters that affect ET simulation in APEX model for winter wheat fields managed under conservation and conventional tillage systems, and 2) evaluate the ability of APEX to simulate ET for each of these tillage systems. Tillage system used had an impact on the number and type of APEX parameters that affect simulation of ET. The total number of parameters affecting ET in conservation and conventional tillage fields were 10 and 8, respectively, with only six parameters common in both tillage systems. However, using the identified parameters corresponding to each tillage system, the calibrated APEX model simulated daily, biweekly and monthly ET relatively well in both tillage systems. Average daily and monthly ET computed by the calibrated APEX model were within 3% of average measured ET in both the conservation and conventional tillage fields located in central Oklahoma. The results of this study contribute to the USDA Agricultural Research Service Long-Term Agroecosystem Research (LTAR) network that seeks to evaluate current and develop sustainable evaluate current and develop sustainable agricultural production systems.

Technical Abstract: The Agricultural Policy/Environmental eXtender (APEX) is one of the hydrologic and water quality models being used in the USDA-ARS Long-Term Agroecosystem Research (LTAR) to evaluate current and develop sustainable agricultural production systems throughout the United States. Tillage practices used affect agricultural production, soil erosion, and evapotranspiration (ET), which is a major component of the hydrologic cycle. However, there is limited literature on the impact of tillage practices on parameterization and performance of APEX to simulate ET. The goals of this study were to 1) determine model parameters that affect ET simulation in APEX model for winter wheat (Triticum aestivum L.) fields managed under conservation and conventional tillage systems, and 2) evaluate the ability of APEX to simulate ET for each of these tillage systems. Tillage system used had an impact on the number and type of APEX parameters sensitive for simulation of ET. Therefore, it is essential to perform a sensitivity analysis for study areas with different tillage management practices to determine appropriate parameters for inclusion in the calibration process. Overall, APEX simulated daily, biweekly, and monthly ET relatively well for both tillage systems. The Nash-Sutcliffe efficiency (NSE) for the simulated monthly ET of the calibrated model was 0.98 and 0.96 for conservation and conventional tillage fields, respectively. The percent bias (PBIAS) values for the ET simulation were within 3%, which indicates that the average simulated ET values were within 3% of the average measured ET in both conservation and conventional tillage fields. This result indicates that a well-calibrated APEX model using appropriate sensitive parameters can simulate ET satisfactorily for both tillage systems in central Oklahoma.