Effects of plant density on some quantitative and qualitative characteristics of Thymus pubescens Boiss. & Kotschy ex Celak under rainfed conditions in three provinces of Iran

In order to study the effect of plant density on some quantitative and qualitative characteristics of Thymus pubescens Boiss. & Kotschy ex Celak under rainfed conditions, a field experiment was conducted in a randomized complete block design with three replications in three different dry farming regions of the country during two years. Experimental treatments consisted of plant density (25, 35 and 50 cm between plants on rows equal to 8, 6 and 4 plant/m2, respectively), time (first and second year after planting) and location (East Azarbayjan, Kordestan, and Tehran). The traits including plant height, canopy diameter, dry matter yield of aerial parts, essential oil yield and content were measured at full flowering stage. The results of ANOVA indicated the significant effect of density, location and time and their interaction on all traits studied. The highest dry matter yield (1147 kg ha-1) was obtained in both two years in Tehran at 8 plant/m2. Kordestan with 2.25% and East Azarbayjan with 0.43% had the highest and lowest essential oil percentage, respectively. In density × location interaction, the highest amount of essential oil yield was obtained in Kordestan (21.73 kg ha-1) and Tehran (17.88 kg ha-1) at a density of 8 plant/m2. Thymus pubescens showed higher dry matter and essential oil yield under high plant density, indicating the establishment and adaptation of the species to different rainfed regions of the country especially Damavand and Kordestan.