Allelopathic effect of harmel (Peganum Harmala L.) on germination and growth of three weeds

Nowadays, in response to the consequences of herbicide application and gradual reduction of farm crops, suitable biological methods have been identified to control the weeds. This research was conducted to evaluate the allelopathic effect of harmel (Peganum Harmala L.) on seed germination of oat (Avena fatua L.), fat hen (Chenopodium album L.) and pig weed (Amaranthus retroflexus L.) in laboratory and greenhouse conditions using hydroalcoholic extracts of harmel dried fruit powder. The treatments were 0.1, 0.25, 0.5, 1, 2.5 and 5% extract of harmel and distilled water (control). Laboratory results indicated that germination percentage and radicle and plumule lengths of weed species were significantly reduced by different harmel extracts in comparison with control. According to the results of greenhouse experiments, germination percentage, fresh and dry weight and height of weed species were significantly reduced by using hydroalcoholic extracts. Greenhouse results also showed that seed germination percentage of Chenopodium album, Amaranthus retroflexus and Avena fatua at concentration of 1% was reduced 60%, 50% and 40% respectively in comparison with control. Our results showed that harmel extract had strong allelopathic effects and inhibited seed germination of weeds recommended in production of natural herbicides.