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１９９４～１９９７年在艾俄瓦中部地区进行了长期的试验研究，用博恩比法测定黑麦、燕麦覆盖地及裸地土壤的净辐射、土壤显热及潜热。研究的目的是评价非生长季节黑麦、燕麦覆盖地及裸地土壤的表面能的分布，并研究此阶段蒸发蒸腾作用的显著性及各地块中蒸发蒸腾作用的不同之处。结果表明：在非生长季节各地块的蒸发量是相当大的，其是年度水文平衡中重要的组成部分，而且１９９４～１９９５年各地块蒸发量差别不大，但１９９６～１９９７年各地块蒸发量差别则很大。
Long-term experimental studies were conducted in Central Iowa during 1994-1997. The net radiation, soil sensible heat and latent heat of rye, oat covered and bare soil were determined by the Bourbon method. The purpose of this study was to evaluate the distribution of surface energy of rye, oat and bare soil in the non-growing season, and to study the significance of evapotranspiration and the differences of evapotranspiration in different plots. The results show that the evaporation of all plots in the non-growing seasons is quite large, which is an important part of the annual hydrological balance, and there is not much difference in evapotranspiration between 1994 and 1995. However, from 1996 to 1997, The difference between block evaporation is great.