The crop coefficient (Kc) values decreased by an average of 35% due to use drip irrigation with plastic mulch which reduced soil evaporation compared with non-mulched treatments (DI and SI), as shown in ( Fig. 3). These results are in agreement with those of Safadi (1991), Vickers (2001) and Mata et al. (2002). Also when we compared it with cucumber crop coefficient values given in Allen et al. (1998), we noted that the Kc values almost similar to ones which were calculated in SI treatment.