Effects of Harvest Intensities on Tragacanth Gum Production and Health of Astragalus Verus

In recent decades, tragacanth gum extraction from Astragalus verus has dramatically increased across Iranian rangelands. However, little information is available about the best method of gum harvest, which is economically efficient and maintains the health of the plant. This research was conducted as a factorial combination and in a completely randomized design, during spring and summer of 2018-2019, at Baraghban rangeland. Three levels of stem cuts (i.e. 1, 2, and 3 cuts on the main stem of each plant) and four frequencies of gum removals (1 to 4 times) with 10 replications were applied on 120 individual plants. Results indicated that all cut and gum removal levels significantly reduced the vigor of A. verus, but no significant relationship was detected between gum removal levels and plant vigor. There was an increase in the gum yield by increasing the number of gum harvests, but no increase was found by increasing cut numbers. Based on the ecological and economic comparisons (estimating costs and benefits), we suggest one cut and four times of gum removal as the most suitable method.