This research was conducted to determine water-yield functions of Cuore (Lactuva Sativa L. var. Longifolia) lettuce cultivars under open field conditions at research station of Konya Soil, Water and Deserting Control Research Institute during 2017-2018 growing season. In the study, four different irrigation treatments were constituted as 60 % (I60), 80% (I80), 100% (I100) and 120% (I120) of the cumilative evaporation measured from the Class A Pan within 4 days period. The experiment was conducted according to randomized block design with three replications.
According to research results, maximum evaportanspration rate was measured in I120 treatment as 441.9 mm while minimum evapotranspiration was measured in I60 treatment as 317.8 mm. The highest average marketable head weight was obtained at I120 treatment with 865.85 g and the lowest average marketable head weight was obtained at I60 treatment with 475.68 g. Irrigation water use efficiency and water use efficiency varied between 14.6-18.3 kg m-3 and 12.5-17.0 kg m-3, respectively, depending on the treatments. The yield response factor (ky) was found as 1.38 100 % of the cumilative evaporation of the Class A Pan is recommended as a optimal irrigation program for drip irrigated lettuce crop under field condition to get higher and quality lettuce yield for the Konya Region.