ESTIMATION OF EVAPOTRANSPIRATION FROM A MILLET CROP IN THE SAHEL COMBINING SAP FLOW, LEAF-AREA INDEX AND EDDY-CORRELATION TECHNIQUE

Within the framework of HAPEX-II-Sahel, evapotranspiration from a millet crop has been measured during a 2 month period from the middle of the rainy season to the beginning of the dry season. The measurements comprise continuous recording of sap flow from a number of millet plants and of evapotranspiration using the eddy correlation technique. It is shown how the leaf area index may be used for transferring the sapflow rates into areal estimates of transpiration. Emphasis is put on the analysis of the sapflow measurements. The diurnal and seasonal variations are analysed in relation to leaf area, leaf temperature and stomatal resistance.