This study was conducted to estimate the water requirements and determine the single and basal crop coefficients (K_c and K_cb) of Moringa oleifera during various growth stages over the cropping years 2023 and 2024. To this end, six drainage lysimeters were employed; three were used to measure the actual evapotranspiration (ET_c) of the crop, and three were used to measure the reference evapotranspiration (ET_o) in a field environment. ET_owas calculated using meteorological data and the Penman-Monteith method. The crop coefficients (K_c) were evaluated for three primary growth stages: initial, development, and mid-season. Subsequently, the single and dual crop coefficients for Moringa oleifera were calculated using the appropriate mathematical formulations.

The results indicated that in the semi-arid region of Kermanshah, the maximum and minimum daily evapotranspiration for the crop was 11.11and 0.45mm, respectively, while for the reference plant, it was 5.63and 2.08mm. In 2023, the K_cvalues for the initial, development, and mid-season stages were 0.71, 1.59, and 1.70, respectively, and in 2024, they were 0.69, 1.32, and 1.76. The average single crop coefficients across the two years were 0.75, 1.71, and 1.715for the initial, development, and mid-season stages, respectively. Similarly, the average basal crop coefficients (K_cb) for the initial, development, and mid-season stages were 0.485, 0.92, and 0.805. These findings provide a scientific basis for the efficient irrigation management of Moringa in regions with similar climatic, soil, and water conditions. Furthermore, the obtained crop coefficients (K_c and K_cb) offer critical insights into the precise water requirements of Moringa in semi-arid climates, serving as a key tool for optimal water resource management. By providing accurate water consumption patterns, these results establish a foundation for enhancing irrigation efficiency in the expansion of this medicinal-industrial crop in water-limited regions.