Study on effects of plant density and harvesting time on vegetative yield and essential oil amount of Thymus daenensis

Thymus daenensis is one of the most important endemic medicinal herbs in Iran which grows in most parts of the country. This study carried out for 3 years since 2004 to determine appropriate plant density and harvesting time for this plant. The firs year was for plant establishment. The experimental design was factorial in randomized complete block design with 3 replications. Measurements started since 2nt year and statistical analysis carried out at the end of 3rd year analyzed with split plot design. Plant density was in 3 levels, 57000, 80000 and 133000 plants/ha and harvesting time with 3 levels, growing stage (before blooming), blooming and flowering. Plant height, cover, fresh and dry weight, essential oil percentage and oil yield were measured. Results were analyzed by each year at first and combined at the end of the last year. According to the results: Dry weight significantly (P 0.01) affected by harvesting time, plant density and year. The highest rate was in flowering stage (7795.1 kg/ha), 133000 plant/ha (7741.6 kg/ha) and in the 2nd year of measurement (8412.53 kg/ha). Fresh weight significantly (P 0.01) affected by harvesting time, plant density and year. The highest rate was in flowering stage (26477.3 kg/ha), 133000 plant/ha (30165.2 kg/ha) and in the 2nd year of measurement (31665.67 kg/ha). Plant height significantly (P 0.01) affected by harvesting time, plant density and (P 0.05) for year. The highest rate was in flowering stage (19.80 cm), 133000 plant/ha (17.28 cm) and in the 2nd year of measurement (16.74 cm). Plant coverage significantly (P 0.01) affected by harvesting time, plant density and year. The highest rate for each plant was in flowering stage (699.44 cm2), 57000 plant/ha (689.44 cm2) and in the 2nd year of measurement (708.26 cm2). Essential oil percentage significantly (P 0.01) affected by harvesting time and year. The highest rate was in flowering stage (2.39%) and in the 2nd year of measurement (2.23%). Essential oil yield per hectare significantly (P 0.01) affected by harvesting time, plant density and year. The highest rate was in flowering stage (47.46 kg/ha), 133000 plant/ha (39.63 kg/ha) and in the 2nd year of measurement (47.38 kg/ha).