Er-Raki S. auteur aut IRD Chehbouni Abdelghani auteur aut IRD Guemouria N. auteur aut IRD Ezzahar J. auteur aut IRD Khabba S. auteur aut IRD Boulet Gilles auteur aut IRD Hanich L. auteur aut IRD text journalArticle eng The aim of this study was to use the FAO-56 single and dual crop coefficient approaches to estimate actual evapotranspiration (ETa) over an irrigated citrus orchard under drip and flood irrigations in Marrakech, Morocco. The results showed that, by using crop coefficients suggested in the FAO-56 paper, the performance of both approaches was poor for two irrigation treatments. The Root Mean Squared Error (RMSE) between measured and simulated ETa values over the citrus orchard under drip irrigation was about 1.43 and 1.27mm/day for the single and dual approaches, respectively, while the corresponding statistics for the orchard irrigated by the flooding technique was 1.87 and 2.48mm/day. After determination of the appropriate values of the crop coefficient (Kc) based on eddy covariance measurements of ETa, the performance of both approaches greatly improved. The obtained Kc values were lower than the FAO-56 values by about 20%. The low Kc values obtained reflect the practice of drip irrigation for one field and the low value of cover fraction for the other field. Additionally, the efficiency of the irrigation practices was investigated by comparing the measured Kc for two fields. The results showed that a considerable amount of water was lost by direct soil evaporation from the citrus orchard irrigated by flooding technique. specialized Crop coefficient drip and flood irrigation citrus orchard semi-arid region 072 143 1 201-208 2009 1126-3504 https://www.documentation.ird.fr/hor/PAR00003520 10.1080/11263500802709897 1126-3504 https://www.documentation.ird.fr/hor/PAR00003520 IRD - Base Horizon / Pleins textes 2009-06-08 2017-08-23 PAR00003520 fre