Investigating the effects of organic and chemical fertilizers on the quantitative and qualitative yield of Satureja sahendica Bornm. essential oil

Savory (Satureja spp.) has a special position among medicinal plants due to its valuable compounds, such as thymol and carvacrol. Savory is one of the genera of the Lamiaceae family, and this genus has 16 species of annual and perennial herbaceous plants in Iran. Due to the high amount of essential oil, Satureja species are highly economically and medically important in the food, cosmetic, health, and pharmaceutical industries. This research aimed to increase the quantitative and qualitative yield of Satureja sahendica Bornm. essential oil with appropriate plant nutrition. This research was carried out under irrigation conditions in the form of a randomized complete block design with eight fertilizer treatments (no fertilizer, N50, P25, K25(kg.ha-1), Cow Manure(30, 60 ton.ha-1), Cow Manure(30, 60 ton.ha-1)+ N50, P25, K25(kg.ha-1), Vermi-compost(5 ton.ha-1), Vermi-compost(5 ton.ha-1)+ N50, P25, K25(kg.ha-1)) in three replications over four years (2017-2020) in East Azarbaijan province. Cultivation was indirect and through grafting. Seedlings were prepared in greenhouse conditions by growing seeds in seedling trays with a mixture of peat moss, cocopeat, and perlite in a ratio 4:2:1. The treatments were applied only once, simultaneously with the plot preparation and before the planting stage. This was done by hand spraying and mixing with the soil. The plot dimensions were 4 x 3 meters, the distance between the planting lines was 50 cm, and the distance between the plants on the line was set to 30 cm. The irrigation method was drip irrigation twice a week in the early stages of growth and once a week after establishment. Weed weeding was also done during the growing season. Plant height, flowering date, crown area, and green shoot yield were measured during the cropping season. Essential oil was extracted by distillation with distilled water, and essential oil was analyzed by gas chromatography (GC) and gas chromatography coupled with mass spectrometry (GC/MS). Based on the results, all traits showed a significant difference between different fertilizer treatments. The highest yield of flowering branches was 1974 kg.ha-1 (6% increase compared to the control) and the yield of essential oil was 22.25 kg.ha-1 (9% increase compared to the control), and the highest quality of essential oil (sum of phenolic compounds thymol and carvacrol) is 61.89% (18% increase in comparison to the control) with treatment of Cow Manure(60 ton.ha-1)+ N50, P25, K25(kg.ha-1) were obtained. To be economical, cow manure (60 tons per hectare) can also be used alone. With regards to 50% flowering, the latest product was a control treatment (without fertilizer) with 160.25 days, while the earliest product was Cow Manure (60 tons.ha-1) +N50, P25, K25 (kg.ha-1) with 155.33 days. The main components of the essential oil were Thymol, p-cymene, and γ-terpinene, respectively. The results of the average percentage of phenolic compounds thymol and carvacrol as essential oil quality in each fertilizer treatment and each year showed that the average quality of essential oil in the first year was 53.13%, in the second and third years it was 63.98 and 63.54, respectively. The percentage decreased to 47.93% in the fourth year. The use of fertilizer treatments, especially animal manures, along with chemical fertilizers, in addition to increasing yield, also causes early ripening. Early harvesting of the first layer allows the second layer to use the growing season optimistically and avoid autumn cold. As the plant age increases, the yield of essential oil increases, but the product is later, and the quality also decreases. Accordingly, Cow Manure(60 ton.ha-1)+ N50, P25, K25(kg.ha-1) should be applied to S. sahendica until the fourth year to produce adequate yields.