Determination of evapotranspiration and basal crop coefficient of alfalfa with a weighing lysimeter Bogachan Benli a, * , Suleyman Kodal b , Adem Ilbeyi c , Haluk Ustun c a International Center for Agricultural Research in the Dry Areas (ICARDA), P.O. Box 5466, Aleppo, Syria b Ankara University, Agricultural Faculty, Department of Farm Structures and Irrigation, 06110 Diskapi, Ankara, Turkey c Ankara Research Institute of Rural Services, PK. 253, Bakanliklar, Ankara, Turkey Accepted 10 May 2005 Available online 21 June 2005 Abstract The aim of this study was to determine the evapotranspiration and basal crop coefficient of alfalfa with a weighing lysimeter. Lysimeter experiments were conducted at Ankara Research Institute of Rural Services, Turkey during 1995–1997. Penman–Monteith, Makkink (FAO-radiation (FAO-Rad)) and Penman-FAO methods performed satisfactorily for estimating the reference evapotranspiration of alfalfa in semi-arid climate conditions. Measured evapotranspiration rates were 1470, 1557 and 1161 mm in 1995, 1996 and 1997, respectively. Basal crop coefficients were computed from evapotranspiration measurements and weather data. The estimated values of the basal crop coefficients for alfalfa at the four growth stages of an individual cutting period were 0.71, 1.78 and 1.51 for initial, mid and late season, respectively. # 2005 Elsevier B.V. All rights reserved. Keywords: Alfalfa; Evapotranspiration; Reference evapotranspiration; Basal crop coefficient www.elsevier.com/locate/agwat Agricultural Water Management 81 (2006) 358–370 * Corresponding author. Tel.: +963 21 2213433; fax: +963 21 2213490. E-mail address: b.benli@cgiar.org (B. Benli). 0378-3774/$ – see front matter # 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.agwat.2005.05.003