Response of Echium amoenum L. as a Medicinal Plant to Organic Fertilizers and Plant Density

Many plant species in natural Iranian ecosystems such as Echium amoenum have high medicinal and economic potential use. The growing need for medicinal products of this plant along with the increasing domestic consumption, export and prevention of its extinction due to its over harvesting from natural ecosystems, necessitates its mass cultivation. E. amoenum is one of the medicinal plants that has important compounds in its flowers, which is necessary to increase the quantity and quality of its flowers. In general, environmental and management factors affecting canopy structure have a significant effect on flower production in these plants. Therefore, for the successful cultivation of any medicinal plant, including E. amoenum, providing optimal environmental conditions such as the best fertilizer combination to meet the nutritional needs of the plant is a priority. Adding organic matter from various sources to the soil is one of the most common regenerating operations to improve soil properties.

In order to better understand the agronomical potential of E. amoenum as a medicinal plant at field condition, an experiment was conducted in a factorial layout based on a Randomised Complete Block design with three replications at Agricultural Research Station, Ferdowsi University of Mashhad, Iran during growing season of 2009-2012. The experimental treatments were all combination of four levels of organic fertilizers (cow manure (30 t.ha-1), compost (20 t.ha-1), vermicompost (5 t.ha-1) and control) and four plant densities (4, 6, 8 and 10 plants.m-2). In April 2010, bed preparation was done by ploughing and levelling the soil and fertilizer treatments were mixed with soil. Cultivation operations were carried out in the first week of May 2010. Irrigation was performed every seven days. During the growing season of 2010, the plants produced mild stems and spent the entire season as a rosette. By autumn and winter, the aerial parts of the plant were dried and in early March 2011, with increasing ambient temperature, the leaves of the plant began to reappear from the crown. Flowering of the E. amoenum in the second year, 12 months after sowing began on April 25, 2011 and the flowering period lasted one month. The flowers were harvested in four stages every seven days. Flowering of the plant began in the third year on May 15, 2012, and the flower harvesting was carried out in five stages, every five days. At each harvest stage, fresh flower yield, dry flower yield and number of flowers per five grams of flowers were determined. After flowering, three plants were randomly marked and plant height, number of main and lateral branches and number of flowers per plant were recorded.

E. amoenum has only vegetative growth in the first year. The results of second and third years showed that studied treatments had significant effect on plant height, number of main and lateral stem branches, number of flower per plant, fresh and dry flower yield. Result showed that by increasing of plant density, fresh and dry flower yield and number of flower (at five g) were increased but number of lateral stem branches and number of flower per plant were decreased. Application of organic fertilizers increased fresh and dry flower yield, plant height, number of lateral stem branches and number of flowers per plant. Additionally, the highest fresh and dry flower yield, number of flower and number of flower per plant and number of main stem branches were obtained in the first year but the highest plant height and number of lateral branches were observed in the second year.

Due to the fact that E. amoenum is an unlimited growth plant, therefore, proper density adjustment is especially important during reproductive growth period. Increasing density during this period causes the plant to have fewer resources (space, water and food) to increase vegetative growth and, as a result, establish a proper balance between vegetative and reproductive growth and produce more flowering shoots and increase flower yield will result. Overall, it seems that application of organic fertilizers and optimum plant density are among more important factors for E. amoenum flower production.
Acknowledgements
Conducting this research was funded by Ferdowsi University of Mashhad, Faculty of Agriculture (Grant No. 66, 25 May 2010).