Comparison of allelopathic effects of aqueous extract of two Achillea species (Achillea nobilis L. and Achillea pachycephala Rech. F.) on Amaranthus retroflexus L.

Due to environmental hazards and risks of chemical control of weeds, sustainable weed management is considered. A concept interactions of interference in plants is allelophatic effects. Which can play an important role in control weeds. Achillea L. is one species of plants with allelophatic activity. By considering abundance of Achillea species in Iran, an experiment in the years 2013-2014 on the collection Achillea species Isfahan University of Technology was implemented. In this experiments aqueous extract from two Achillea species collected from different area in Iran, including A. nobilis (of Isfahan), A. pachycephala (of Golestan) and A. pachycephala (of Hamadan) on Amaranthus retroflexus at concentrations of 0, 3, 6, 12, 25, 50 and 100 percent was performed. The results showed that various concentrations of aquous extract have different effects on species and their characteristics. The genotype A. pachysephala of Hamedan have stronger effect and genotype of Golestan have the lowest effects. Extracts in concentrations between 3 to 12% have a stimulatory effect and in concentrations of 25 to 100% showed inhibitory effect.