Evapotranspiration rates over a crop of sunflower of the giant variety as estimated by the energy balance method

Abstract

In this study the energy balance approach is applied to determine the evapotranspiration rates over a crop of sunflower of the giant variety. Three series of measurements were taken when the crop was 1 meter high, 1! meters high and 3 meters high. The technique used is that of the Bowen ratio method which consisted of hourly values of dry bulb temperature, wet bulb temperature and wind speed at two levels above the crop from 8 a.m. to 5 p.m. local time. Furthermore flux measurements were made and these consisted of net radiation and soil heat flux. The instruments were mounted on an aluminium mast which permitted the alteration of the positions of the·instruments with plant growth.