Determination of optimum planting density for forage alfalfa (Medicago sativa L. var:Yazdi) under saline condition

This experiment was carried out with two levels of salinity of irrigation water of 2 and 8 dS/m in a randomized compelete block design with 3 replicationsand for two years. Tretments in each level of salinity were 6 seed rates including: 10, 15, 20, 25, 30 and 35 Kg.ha-1 of Yazdi alfalfa variety. Number of cuts was 5 times annually at 10% of flowering in experimental plots. Results showed that, seed rate affected total fresh matter yield (TFMY) at 1% level of probability in each level of salinity of irrigation water for two years, annually. The effect of seed rate on total dry matter yield (TDMY) was significant at 5% and at 1% level of probability in the 1st and 2nd year of experiment, respectively. TFMY obtained with 8dS/m irrigation water was 11.67% and 17.37?% less than that of 2dS/m in 1st and 2nd year of experiment, respectively. For TDMY of salinity of 8dS/m was 7.06% and 12.53% less than 2dS/m for 1st and 2nd year, respectively. Upon combined analysis of the experiment, the effect of seed rate on TFMY and TDMY was significant at 1% level of probability in both 2 and 8 dS/m irrigation waters. Maximum TFMY with 2dS/m irrigation water was obtained in the seed rate of 30Kg/ha-1 with the yield of 88516 kg.ha-1 and other seed rates of 10, 15, 20, 25 and 35 kg.ha-1 produced 27.18%, 22.09%, 5.72%, 5.82% and 2.53% less, respectively. In 2dS/m irrigation water, DMY of 20, 25, 30 and 35 kg.ha-1 of seed rate were placed in same statistical group. Maximum FMY wuth irrigation water of 8dS/m was obtained in the seed rate of 35 kg.ha-1 with the rate of 76949 kg.ha-1 and other seed rates of 10, 15, 20, 25 and 35 kg.ha-1 produced 29.21%, 20.68%, 14.35%, 5.80% and 3.32% less, respectively. In 8dS/m irrigation water, maximum of TDMY obtained in 35 kg.ha-1 of seed rate which were not significantly different with seed rate of 25 and 30 kg.ha-1. Based on the above it could be concluded that to obtain higher yields under saline condition seeding rates should be increased.