عنوان مقاله [English]
Sage is a popular medicinal plant which is widely used in food and pharmaceutical industries. Vermicompost are a rich source of macronutrients, micronutrients, vitamins, enzymes and plant growth promoter hormones. Therefore, the use of vermicompost in sustainable agriculture, in addition to increasing population and activity of beneficial soil microorganisms, causes the rapid growth of medicinal plants. The uses of bacteria (Azotobacter, Azospirillum and Pseudomonas) as a biofertilizer have causes increasing the efficiency of nitrogen and phosphorus fertilizers and improving the growth of several crops. Drought stress is one of the most important environmental stresses that affect the growth and yield of plants. Management of nutrients in plants, especially during drought conditions and to assess this management on quantity and quality of sage medicinal plant is very important. Limited information are available about the response of sage under water deficiency conditions in different fertilizing systems, so the aim of this research was to study the growth, yield and essential oil production of Sage under different irrigation regimes.
Materials and methods
Field experiments were carried out at the field research station of Faculty of Agriculture of Tarbiat Modares University in Tehran, Iran during two growing seasons (2011-2012 and 2012-2013).
The experiment was laid out in split plot based on randomized complete block design with three replications. Three irrigation levels including irrigation after depletion of 40% available water (I1), irrigation after depletion of 60% available water (I2), irrigation after depletion of 80% available water (I3) as the main plots and five different soil fertility systems including control (no fertilizer) (F0), chemical fertilizer (urea=150 kg/ha-1) (Ur), nitrogen fixing bacteria(Azotobacter+Azospirillum+Pseudomonas) (NFB), vermicompost (8 t/ha-1) (V) vermicompost + nitrogen fixing bacteria (V+NFB) as sub plots were allocated. A TDR probe (Time-Domain Reflectometry, Model TRIME-FM, England) was applied to measure soil water content. Essential oil extraction was subjected to conventional hydro distillation using a Clevenger-type apparatus in accordance. Essential oil analysis was performed using a TRACE GC (ThermoQuest-Finnigan) equipped with a DB-5 fused silica column (30 m × 0.25 mm, 0.25 μm film thickness). GC–MS analyses were carried out on a TRACE MS (ThermoQuest-Finnigan).
Results and Discussion
The highest plant height, canopy diameter, leaf area and dry matter yield were obtained at no stress and V+NFB in all three harvests. Also, the maximum essential oil content and essential oil compounds were obtained at moderate stress and V+NFB in all three harvests. Among the three times harvest, the highest plant height (28.84 cm), canopy diameter (29.58 cm), leaf area (1.77 m.m-2) and dry matter yield (296 g. m-2) were observed at third harvest time. The maximum essential oil content (1.90%) was obtained at second harvest time and the highest α-thujone (32.73%), 1, 8- cineol (10.91%) and camphor (32.47%) were observed at third harvest time.
Reduction in the morphological characteristics and dry matter by increasing drought stress could be the result of a preferential allocation of biomass production to the roots or a reduction in chlorophyll content and photosynthesis efficiency.Positive and synergistic effects between vermicompost and bacteria can increase bacterial activity in the soil and rhizosphere through mechanisms such as production of growth hormone which increased root growth. Increasing in essential oil concentration under water stress could be due to the fact that plants produce high terpene concentrations under water stress conditions and low allocation of carbon to the growth, therefore can be a trade-off between growth and defense. Vermicompost and nitrogen fixing bacteria by providing more uptake of phosphorus and nitrogen increase the essential oil content.
The results showed that drought stress reduced the growth characteristics (height, canopy diameter and leaf area), and the highest amounts of essential oil content and quality were observed in moderate stress. In addition, vermicompost + nitrogen fixing bacteria treatment was the best fertilizer combination among all treatments in increasing the growth characteristics, dry matter yield, and essential oil quantity and quality.