Evaluation of direct and indirect methods used to determine crop coefficient and crop evapotranspiration of sugar beet plants grown under fayoum conditions

With increasing water scarcity, the determination of reference evapotranspiration ETo and crop coefficient (Kc) is a critical factor in determining the crop water demand ETc. Therefore, the current investigation aimed to evaluate and compare the estimated sugar beet crop evapotranspiration (ETc) values computed by different empirical methods (e.g. Hargreaves, Penmen-Monteith and Class-A pan) with the measured actual sugar beet evapotranspiration (ETa). To determine the ETa for sugar beet crop field experiment was conducted during two growing seasons (2019/2020 and 2020/2021) in Demo farm, Faculty of Agriculture, Fayoum University, Egypt. Sugar beet seeds (Beta vulgaris L., Baraca) was planted in 1st October and harvested in April during two successive winter seasons. Irrigation water was applied when the soil moisture content was depleted by 30% of available water. All the obtained results were statistically analyzed to evaluate the best method for estimating the reference evapotranspiration and suitable for optimizing the irrigation management practices for sugar beet plants grown under arid and semi-arid conditions. The obtained results concluded that among the used methods (Hargreaves, Penmen-Monteith and Class A pan) for estimating sugar beet crop evapotranspiration (ETc) in comparison with ETa measured values, the Penmen-Monteith performed well in describing the ETc and Kc for sugar beet plants grown in Fayoum Governorate, Egypt.