Effect of Irrigation and Plant Density on Yield and Growth Indices of Purple Coneflower (Echinacea purpurea (L.) Monch)

Purple coneflower is one of the most important medicinal plants known for its anti-bacterial and anti-virus effects. This perennial herb from the Asteraceae family is native to North America and is planted widely in Europe. All parts of the plant contain useful chemical compounds such as Chicoric acid, Isobutyl, Polysaccharides, and Essential oils. Planting population and the amount of water applied are important management practices for all crops, particularly medicinal plants, due to a prefund effect of these parameters on the chemical constituents of these plants. An optimum planting population of 25 plants per m2 is normally practiced for Purple coneflower, but higher populations of up to 40 plants per m2 have also been reported. Water stress has been reported to increase Chicoric acid and Folic acid but not Essential oils. The purpose of the present study was to evaluate plant density and the amount of irrigation water on different agronomic criteria of Purple coneflower under climatic conditions of Mashhad.

In order to investigate the effects of different irrigation levels and plant density on yield and other criteria of Purple coneflower, an experiment was conducted at the Agricultural Research Station of the Faculty of Agriculture, the Ferdowsi University of Mashhad during the years 2009-2010 and 2010-2011. A split plot based on a randomized complete block design with three replications was conducted. Irrigation with four levels at 50, 100. 150 and 200 mm evaporations from evaporation pan class A were allocated to the main plots, and two plant densities of 20 and 30 plants per m2 were used as subplots. Leaf area index, dry matter yield, plant height, number of branches, number of flowers per plant, average flowers weight per plant, number and dry weight of flowers per plant, number of flowers per unit area, fresh and dry weight of flower and root dry weight were recorded.

Results showed that all the investigated criteria were affected by irrigation levels. Plant density also affected all criteria except those of weight per flower and fresh flower weight per unit area. The highest flower yield per unit area was obtained from 50 mm irrigation level and plant density of 30 plants per m2. The lowest flower yield was obtained from 200 mm irrigation level and 20 plants per m2. However, irrigation levels of 50 and 100 mm and plant density of 30 plants per m2 were the most promising practices for maximum flower yield.

Since irrigation levels and plant density are two important factors affecting most plant criteria, it is important to investigate these practices for crop production, particularly in medicinal plants where chemical compounds are also sensitive to these two parameters. For Purple coneflower, it appears that irrigation levels of 50 and 100 mm and plant density of 30 plants per m2 are practices that can be recommended, though more investigations are required to make assurance.
Keywords: Dry Matter, LAI, Medicinal plant, Water stress