Effect of aqueous extracts of allelopathic crops on germination and growth of Parthenium hysterophorus L.

Herbicidal effects of aqueous root and shoot extracts of three allelopathic crops, viz. sunflower (Helianthus annuus L.), sorghum (Sorghum bicolor L.) and rice (Oryza sativa L.) were evaluated against germination and growth of the noxious alien weed Parthenium hysterophorus L. The study, carried out in petri dishes using 5, 10, 15, 20 and 25% (w/v) aqueous root and shoot extracts of fresh plant materials of the test crops, indicated insignificant effects on shoot length and seedling biomass while germination and root length were significantly reduced by extracts of all the test crops. In a foliar spray bioassay, aqueous shoot extracts of 50 and 100% w/v (on a fresh weight basis) of sunflower and sorghum were applied to 10 day old Parthenium plants. The root biomass of Parthenium plants was significantly suppressed by 50 and 100% extracts of both the test allelopathic extracts. Both concentrations of sorghum extracts significantly reduced shoot biomass, but sunflower extract was effective only at the lower concentration.