Document Type : Research Paper
In order to investigate the effect of water deficit on yield and water use efficiency (WUE) of four alfalfa cultivars, an experiment was conducted as a split plot design in randomized complete block with 3 replications in Agriclture and Natural Resources Research Center of Khuzestan during 201l-2012. Main plots were 4 irrigation regimes (a1: traditional irrigation, a2: irrigation in loss of 50%, a3: irrigation in loss of 65% and a4: irrigation in loss of 80% AWC) and subplots were four cultivars of alfalfa (b1: Baghdadi, b2: Mesasirsa, b3: Yazdi and b4: Hamedani). The result showed that alfalfa total fresh and dry forge yield was significantly affect by water deficit, in all of the cultivars the highest of fresh and dry forage yield was in traditional irrigation that decreased with retardation of irrigation. The Baghdadi cultivar had the highest fresh and dry forage yield in all of irrigation regimes (in traditional irrigation: 75. 57 tn ⁄ ha fresh and 17. 5 tn/ha dry forage yield and in a4: irrigation in loss of 80% AWC this cultivar produced 45.86 tn ⁄ ha fresh and 11.15 tn ⁄ ha dry forage yield ).The water use efficiency increased with retardation of irrigation. The highest of WUE in all of cultivars were in a4: (irrigation in loss of 80% AWC) and the WUE in this treatment for Baghdadi cultivar was 1.00 kg/m3/ha , in mesarirsa cu. was 0.820 , in yazdi cu. Was 0.720 and Hamedani cu. Was 0.580 . The lowest rate of leaf/stem in all of cultivars belonged to traditional irrigation and with decreasing of irrigation to a2(irrigation in loss of 50% AWC) the rate of leaf/stem increased about 22% ( mean in all of cultivars).