Surface Energy Balance and Surface Coefficients of a Corn Field during Non-Growing Periods

摘要

Efficient use of water in agroecosystems requires accurate quantification ofevapotranspiration (ET) during growing and non-growing (dormant) periods.Prediction of ET during the growing season has been well researched, but relativelylittle information exists on evaporative losses during non-growing periods. Theobjective of this research was to evaluate ET in relation to available energy,precipitation, and reference ET for a corn field during the non-growing period(October 15 through April 30). Three consecutive non-growing periods were studied:2004-2005 (season I), 2005-2006 (season II), and 2006-2007 (season III). Bowenratio energy balance system-measured ET was approximately 50% of availableenergy during average and wet seasons (seasons I and III) and 41% of availableenergy during a dry season (season II). Cumulative ET ranged from 133 to 167 mmand exceeded precipitation by 21% during the dry season. Mean surface (crop)coefficients were 0.63 and 0.48 for grass and alfalfa-reference crops, respectively.Regression equations were developed that yielded reasonable estimates of ET for theaverage and wet seasons. Considering non-growing period evaporative losses in waterbudget calculations would enable water regulatory agencies to better account forwater use over the entire year rather than only for the growing season.