Changes in the Ratio Between Sugar Beet Evapotranspiration and Pan Evaporation During the Growing Season

Abstract Evapotranspiration by sugar beets and evaporation from a Class A pan were measured at 4‐ and 6‐day intervals during the period November‐May. Plant development and the progressive coverage of the ground by foliage were also followed. The ratio between evapotranspiration and evaporation, which might be used as an indicator of how much irrigation water to apply, changed during the course of the growing season. This change was found to be independent of plant development or ground cover, but was related to evaporative conditions, and even more so to the moisture content of the upper soil layer. The effect of these two factors on the change in the ratio was linear.