the effect of different irrigation treatments on resin yield, essential oil content, morphological traits and survival of bitter asafetida (ferula assa-foetida l.)

bitter asafetida (ferula assafoetida l.) is one of the medicinal-rangeland plants belonging to apiaceae family. the resin which is through incision secreted of the root has medicinal properties. the effect of rain on resin yield of this plant is one of problem of natural resources offices. the main aim of this study was to find out the effects of the irrigation on the resin yield, plants survival and some morphological traits of asafetida plants. five irrigation treatments consisting of two times at week, one time at week, one time at two week, one time at three week, one time at month and without irrigation (control) were employed. the statistical design was a randomized complete block design, with four replications. the results show that irrigation increased resin yield, leaf length, vegetative growth period, survival plants at during of exploitation and next year significantly. but irrigation decrease essential oil percentage of resin significantly. one time irrigation in each week was the best treatment for increasing resin as it had produced 81.4 g resin yield per plant. the lowest resin yield was obtained in control and one time irrigation per month. these treatments had no effect on number of plant leafs. so plants irrigation before exploitation from this plant is recommended.