Application of allelopathy in crop production: Success story from Pakistan

Allelopathy is an emerging field with its wider applications in agriculture and allied disciplines. In Pakistan, work on allelopathy was initiated in the early 1970s with screening of local flora for allelopathic potential in laboratory bioassays, while field studies were taken up during the early 1980s. Sorghum was found the most potent allelopathic plant in this regard, which was used as mulch material, intercrop, and plant water extracts for weed management. Application of sorghum plant water extracts proved more effective in controlling weeds than all other strategies. Several other plants including sunflower, canola, eucalyptus, rice, mulberry, etc. were also evaluated. Although each of the allelopathic sources provided some control, mixtures of allelopathic water extracts were more effective than the application of single plant extracts. To achieve effective weed control, allelopathic extracts were applied together with the lower herbicide dose. Mixed application of allelopathic extracts with one-third to half of the standard herbicide dose provided effective weed control as achieved from the standard herbicide dose in several field crops. Application of allelopathic mulches, soil incorporation of allelopathic residues, and intercropping with strong allelopathic crops also provided effective control of several weeds. In recent years, commercialization of allelopathic extracts for weed management is under way. Allelopathy has also been effective in controlling stored grain and field crop pests in addition to several pathogens which may also be controlled by allelopathy. Allelopathy is also being evaluated as growth promoter; foliar application of canola, sorghum, sunflower, and moringa extracts has been found effective in this regard. More recently, allelopathic extracts are being evaluated for their potential role in improving resistance against abiotic stresses in cereals.