عنوان مقاله [English]
Vermicompost tea can be extracted under aerated or non-aerated (passive) conditions. This water extractable compound includes: Active microorganisms, primarily Bacteria, Fungi and some Protozoa, Mineral nutrients, Organic acids and other microbial by-products. Considerable variability in the efficacy of compost tea to promote plant growth has been reported in many experiments. The results suggest that the reasons for the beneficial effects of the compound are complex and depend on many factors, including plant species, compost quality, extraction method, and growing conditions. They may have direct and indirect effects on plant growth and development. The indirect effects of humic compounds on soil fertility include: (i) Increase in the soil microbial population including beneficial microorganisms, (ii) Improved soil structure and (iii) Increase in the cation exchange capacity and the pH buffering capacity of the soil. Directly, humic acid compounds may have various biochemical effects either at cell wall and membrane level or in the cytoplasm, including increased photosynthesis and respiration rates in plants, enhanced protein synthesis and hormone-like activities in plants. Satureja khuzistanica Jamzad is an endemic species of the genus Satureja in Iran. It is a valuable medicinal plant because of high concentration of Rosmarinic Acid in the extract. This plant also has other unique growth properties such as high growth under calcareous and poor soils of arid region.
Materials and methods:
In order to study the effects of different levels of humic acid and vermicompost tea on growth, yield, morphological and phytochemical characters of Satureja khuzistanica, an experiment with factorial arrangement based on randomized complete block design with three replications was conducted in 2013. Factors included of three levels of humic acid (1.5, 2.5 and 3.5 liter per ha.) and vermicompost tea in concentrations of 5% (5:1, water: vermicompost) 10% and 20% which were sprayed on aerial parts of the plants. Parameters like plant height, plant crown, leaf length, leaf width, shoot dry weight, leaf dry weight, oil content, essential oil yield, content of phenolic and flavonoids compounds were studied in this study to evaluate the effects of the treatments on Satureja Khuzistanica.
The results showed that treatments of 3.5 l.ha-1 humic acid + 20% vermicompost tea had the maximum dry weight (460 g.m-2 ), leaf dry weight (195.33 g.m-2) and essential oil yield (6.38 g.m-2). The highest essential oil percentage (3.44%) was obtained in the treatment of 1.5 l.ha-1 humic acid + 20% vermicompost tea. The maximum content of phenolic and flavonoids compounds were observed in treatments of 2.5 l.ha-1 humic acid + 5% vermicompost tea (46.56 µg gallic acid /mg dry extract) and 3.5 l.ha-1 humic acid + 5% vermicompost tea (749.13 µg routin /mg dry extract), respectively. The interactions of the humic acid and vermicompost tea effects on plant height, plant crown, leaf length and leaf width were not significant in both years.
Results of this experiment showed that mixed application of humic acid and extract of vermicompost (vermicompost tea) has more positive effects on growth and yield parameters of this plant rather than sole application. Results of Azza et al, (2010) showed that the extract of vermicompost can increase yield, oil content and essential oil yield in Levisticum officinalis. Appropriate amounts of humic acid and vermicompost extract can increase soil organic matter by improving the soil microbial activity and nutrient availability, and this will result in increasing the rate of photosynthesis and plant dry matter so this is a way to ultimately improve the yield, leaf dry weight and the essential oil yield of Satureja khuzistanica. Among the treatments, application of 3.5 l.ha-1 humic acid + 20% of vermicompost tea, had the best effects on growth and yield.
Hereby we appreciate Iran National Science Foundation (Science Deputy of Presidency) for financial support of this project (Nr.85125.61) and Khoraman and FTSS companies which support this project and Mr.Ali Karimi (graduated student of medicinal plants, Medicinal Plants and Drugs Research Institute of Shahid Beheshti University) who cooperate us in this research.