Assessment of Different Water Use Efficiency Calculations for Dominant Forage Crops in the Great Lakes Basin

Kevin De Haan, Myroslava Khomik, Adam Green, Warren Helgason, Merrin L. Macrae, Mazda Kompanizare and Richard M. Petrone
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Kevin De Haan: Hydrometeorology Research Group, Department of Geography and Environmental Management, University of Waterloo, Waterloo, ON N2L 3G1, Canada
Myroslava Khomik: Hydrometeorology Research Group, Department of Geography and Environmental Management, University of Waterloo, Waterloo, ON N2L 3G1, Canada
Adam Green: Hydrometeorology Research Group, Department of Geography and Environmental Management, University of Waterloo, Waterloo, ON N2L 3G1, Canada
Warren Helgason: Department of Civil, Geological and Environmental Engineering, University of Saskatchewan, Saskatoon, SK S7N 5A9, Canada
Merrin L. Macrae: Biogeochemisty Lab, Department of Geography and Environmental Management, University of Waterloo, Waterloo, ON N2L 3G1, Canada
Mazda Kompanizare: Hydrometeorology Research Group, Department of Geography and Environmental Management, University of Waterloo, Waterloo, ON N2L 3G1, Canada
Richard M. Petrone: Hydrometeorology Research Group, Department of Geography and Environmental Management, University of Waterloo, Waterloo, ON N2L 3G1, Canada

Agriculture, 2021, vol. 11, issue 8, 1-19

Abstract: Water use efficiency (WUE) can be calculated using a range of methods differing in carbon uptake and water use variable selection. Consequently, inconsistencies arise between WUE calculations due to complex physical and physiological interactions. The purpose of this study was to quantify and compare WUE estimates (harvest or flux-based) for alfalfa (C 3 plant) and maize (C 4 plant) and determine effects of input variables, plant physiology and farming practices on estimates. Four WUE calculations were investigated: two “harvest-based” methods, using above ground carbon content and either precipitation or evapotranspiration (ET), and two “flux-based” methods, using gross primary productivity (GPP) and either ET or transpiration. WUE estimates differed based on method used at both half-hourly and seasonal scales. Input variables used in calculations affected WUE estimates, and plant physiology led to different responses in carbon assimilation and water use variables. WUE estimates were also impacted by different plant physiological responses and processing methods, even when the same carbon assimilation and water use variables were considered. This study highlights a need to develop a metric of measuring cropland carbon-water coupling that accounts for all water use components, plant carbon responses, and biomass production.

Keywords: ecosystem water use efficiency; harvest water use efficiency; alfalfa ( Medicago sativa ); maize ( Zea mays ); fluxpart (flux variance similarity partitioning); eddy covariance (search for similar items in EconPapers)
JEL-codes: Q1 Q10 Q11 Q12 Q13 Q14 Q15 Q16 Q17 Q18 (search for similar items in EconPapers)
Date: 2021
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