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In order to find relative high yielding alfalfa cultivars for conditions of limited irrigation water and also to find high efficiency cultivars for favorable conditions, 77 alfalfa cultivars were studied in two years and four experiments called No.1, No.2, No.3 and No.4. The trails re conducted at the Experimental Station, College of Agriculture, University of Tehran, Karaj, Iran, in 1986 and 1987. The two irrigation treatments for Exps. No.1 and 2 were once every 10 days and every 20 days. Eleven high yielding alfalfa cultivars were marked in the 1986 experiments. The effects of four irrigation treatments including every 10 days, W2= every 20 days, every 30 days and without irrigation were evaluated on 11 selected cultivars in experiment No.3 .The characters studied were yield, plant height, and flowering date.
In experiment No.4 which was conducted in greenhouse, the effects of 50 and 100 percent soil moisture field capacity were studied on two selected high yielding and two selected low yielding cultivars. In this trail, number of internodes, plant height, and length of the first three internodes of primary stems were measured.
Stress Susceptibility Index (SSI) for total yields of cultivars in experiments No.1 and 2S calculated. Among seven alfalfa cultivars, the Bahar-Hamedan and Ahar cultivars had the highest yeild in their second cutting in 1987 in experiments, No.1&2. The Maragheh, Mohadjeran, Ahar, Ardabil, Ardakani-Shahreza, Hamedan and Marandi cultivars had lower SSI, compared to others. In the third experiment, Bami and polycross Bam-lO had the highest yield in and W treatments, in the first cutting. The 2198- Ghasaghestan cultivar had the lowest yield in all irrigation treatments.
The combined analysis of variance for all the four cuttings in experiment No.3 showed that mean square values were significant for cultivars, irrigation, cuttings and irrigation X cutting interaction. The highest yield obtained from treatment. The polycross Yazd-8 cultivar had the highest yield in this experiment.
Irrigation treatments and cultivars had no significant effects on internode numbers in experiment No.4. In 100 percent field capacity, Bami cultivar had higher internode numbers and the length of the first three internodes on this cultivar was also the highest.
The overall results in these studies showed that, in experiment No.1 a total of 10092 Kg/ha drymatter, 3780 Kg/ha for 3 cuttings in 1986 and 6312 Kg/ha for 4 cuttings in 1987, was produced. In experiment No.2 a total yield of 8260 Kg/ha including 3636 Kg/ha in 1986 and 4624 Kg/ha in 1987, was obtained. In experiment No.3, the dry yields in W1,W2,W3 and treatments were 3867 Kh/ha, 2930 Kg/ha, 2094.7 Kg/ha and 956.7 Kg/ha, repectively.