Cultivation and production of some thyme species in different dryland farms of the country

Cultivation and establishment of perennial medicinal plants in the low-yield dryland farms and degraded rangelands can prevent the erosion caused by annual repeated plowing, and create changes in the conservation and restoration of dryland agricultural ecosystems. To prove this hypothesis, several experiments were conducted in the form of a national plan in seven key dryland areas in North Khorasan, Guilan, East Azarbaijan, Kurdistan, Kermanshah, Isfahan, and Tehran during 2007-2011. Field experiments were carried out in a split-plot design, containing species as main plot at 10 levels (10 Thymus species) in different areas, and density as subplot at three levels (4, 6 and 8 plants per square meter). The results of field experiments in different years and different provinces revealed the establishment of all species studied under rainfed conditions. The highest dry matter yield in Thymus daenensis (2994 kg ha-1) and T. kotschyanus (2884 kg ha-1) was recorded for Kurdistan, Kermanshah, and Tehran at a density of eight plants per square meter. The oil yield varied from 0.69-3.11% in different treatments. The highest oil percentage was obtained for T. daenensis in Kermanshah and Kurdistan. According to the results, the increased dry matter yield at high density under rainfed conditions of Kermanshah, Kurdistan, and Tehran indicates the high production capacity of thyme under rainfed conditions with an annual rainfall up to 400 mm and in cold semi-steppe regions.  The highest amount of thymol (80.33%) and carvacrol (71.9%) was recorded for T. daenensis and T. kotschyanus in Damavand. Results indicate the appropriate establishment and yield of local thyme species under rainfed conditions that could be introduced as perennial medicinal plants for dryland farming.