Allelopathic effect of sunflower (Helianthus annuus) rhizosphere soil on germination and seedling growth of kharif crops and weeds.
Laboratory bioassay was conducted to assess the toxicity of sunflower rhizosphere soil against crops and weeds of kharif season. The aqueous extracts (75%, 50% and 25%) of sunflower rhizosphere soil inhibited the germination and seedling growth (shoot length, root length and dry matter accumulation) of all test plants as compared to control. However, the extracts proved most harmful to germination in Parthenium hysterophorus followed by Trianthema portulacastrum, Vigna radiata and Pennisetum glaucum. Aqueous extract of 25% proved to be less harmful to germination in all test plants except Parthenium hysterophorus and inhibitory effect of extract increased with increase of extract concentration. Among all parameters, germination proved most sensitive to applied aqueous extracts.