Effect of vermicompost and some of macro nutrients on plant growth, nutrient uptake and quantity and quality of Savory (Satureja hortensis L.) essential oil

Organic fertilizers are one of the requirements for sustainable agricultural development in order to reduce the use of chemical fertilizers and their environmental hazards. In this regard, vermicompost has an important role in improving the growth and quality of agricultural products and organic production. Numerous studies have been investigated the positive effect of vermicompost on enhancing the quantitative and qualitative yield of medicinal plants. But there is no comprehensive study concerning the impact of vermicompost or combined nutrition on quantity and quality of Savory yield. Therefore, this study was conducted to evaluate the influence of vermicompost and integrated nutrition on growth, nutrient uptake and quantity and quality of Savory essential oil.

This experiment carried out using a randomized complete block design with 12 treatments and three replications. The treatments were included: control (without treatment), chemical fertilizer containing nitrogen, phosphorus and potassium (NPK) (80:50:50 kg/ha), different levels of vermicompost (2, 4, 6, 8 and 10 ton/ha) and combined treatments (50 % of each level of vermicompost + 50 % NPK). Evaluated traits were included: plant height, number of lateral branches per plant, aboveground dry weight, percentage and yield of essential oil, essential oil components, chlorophyll a and b and total chlorophyll and the uptake of nitrogen, phosphorus and potassium. Data were analyzed using SAS software and means were compared using the LSD test (p ≤ 0.05).

The results showed that all of the studied traits except the chlorophyll b and essential oil percentage were significantly affected by treatments. NPK treatment dramatically increased the number of branches per plant, aboveground dry weight, nitrogen and potassium uptake and chlorophyll a and total chlorophyll compared with control. Vermicompost alone or in combination with NPK fertilizer (50 % vermicompost with half dos of NPK) had a significant effect on increasing of all traits (except chlorophyll b and essential oil percentage) depending on the dose applied. Maximum phosphorus uptake was obtained by application of 10 ton/ha vermicompost; While in other traits the highest value was obtained by the 5 ton/ha vermicompost + 50 % NPK. The lowest value of the all evaluated traits was related to control treatment. The results also showed that the lowest percentage of γ-terpinene, p-cymene and myrcene were observed in control plants; whereas, the percentage of carvacrol were significantly increased in control when compared with fertilizer treatments (except 2 and 4 ton / ha vermicompost).

The findings of this study suggested that the application of vermicompost alone (6 ton/ha or more) or in combination with chemical fertilizer (especially at 5 ton/ha vermicompost + 50% NPK) has a good potential in improving dry matter and essential oil yield of S. hortensis. Hence, it is concluded that NPK fertilizers can be eliminated or reduced by using vermicompost in savory agriculture. It can also be concluded that the untreated plants is the most suitable for obtaining the highest percentage of carvacrol; whereas, application of vermicompost alone or in combination with chemical fertilizer is preferable for attaining hydrocarbon monoterpenes such as γ-terpinene, p-cymene and myrcene.