Allelopathic effect of herbal formulation containing Ferula assa-foetida L. essential oil and castor oil (Ricinus communis L.) as an herbicide on Amaranthus retroflexus L. seed germination

Background: Medicinal plant contain phytochemicals which have inhibitory effects on plant pathogens. Weeds compete with the main crops and reduce the growth, yield, and quality of agricultural products to some extent. One of the most common methods of reducing weed damage is the use of chemical herbicides. Due to the side effects that chemical herbicides on human health and the environment, there is a need to replace biocompatible and lowrisk herbicides. Objective: In this study, the allelopathic properties of the Ferula assafoetida L. essential oil and castor oil (Ricinus communis L.) have been investigated as a botanical herbicide to prevent germination of redroot pigweed seeds (Amaranthus retroflexus L.). Methods: In this regard, an herbal formulation based on Ferula assafoetida essential oil and castor oil was prepared and its effect on the germination of redroot pigweed seeds was studies in laboratory conditions. The chemical composition of the herbal formulation was analyzed by GC/MS. Results: The results showed that this herbal formulation in concentration 0.75 % and 1 % inhibits the germination of weed seeds about 70 %. The main constituents of Ferula assafoetida and Ricinus communis were (E)1propenyl secbutyl disulfide (43.9 %) and ricinoleic acid methyl ester (58.1 %), respectively. Conclusion: It was found that the studied botanical formulation has herbicidal properties. Therefore, more research is needed to achieve promising results in order to replace chemical herbicides with botanical herbicides.