Determination of Water Requirement and Crop Coefficient for Sugarcane Using Lysimeter Experiment under Semiarid Climatic Conditions of Ethiopia

Sugarcane is one of the most important industrial crops grown throughout tropical areas. Sugarcane production is greatly expanding in developing countries like Ethiopia due to increasing demand for sugar. However, sugarcane is characterized by a long growing period and high crop water demand. Effective management of sugarcane requires accurate determination of its water requirements throughout the growing period. The aim of this study was to determine sugarcane water requirements and establish its crop coefficient. Sugarcane was grown on two non-weighable lysimeters to quantify the field water balance components from which actual crop evapotranspiration was calculated. A neutron probe was used to monitor change in moisture content per unit of time. The soil moisture in the lysimeters was managed such that optimum conditions were maintained to ensure unrestricted crop evapotranspiration. Reference evapotranspiration was estimated using climate data from a nearby station and the CROPWAT model. Sugarcane evapotranspiration ranged from 1.63 to $7.13\mathrm{mm}/\mathrm{day}$ during the early and peak growth stages, respectively. The growth stage-based crop coefficients were estimated as 0.42, 0.93, 1.26, and 1.05 during the emergence, tillering, grand formation, and ripening stages, respectively. When compared to Food and Agricultural Organization (FAO) of the United Nations references, the sugarcane crop coefficients in this study were 2%, 1%, and 30% greater during emergence, grand formation, and ripening, respectively, but 33% lower at tillering. Although these results were obtained from a single experiment, they can be useful as field measurement-based data are lacking in many areas of the region.