Determination of Allelopathic Activity in Dominant Upland Weeds

Allelopathic activity of dominant upland weed species was determined using aqueous and methanol extracts and dried residues of the weeds. Germination and seedling growth of radish (Raphanus sativus L.) and sesame (Sesamum indicum L.) were greatly inhibited by 2% (w/v) aqueous extracts of Artemisia asiatica Nakai and Portulaca oleracea L., respectively. Great phytotoxicity on both indicator plants occurred by 2% (w/v) aqueous extracts of Capsel/a bursa-pastoris (L.) Medik. A complete inhibition in germination and seedling growth of radish was caused by 2% (w/v) methanol extract of A. asiatica. There was about 90% inhibition in germination and seedling growth of sesame due to 2% (w/v) methanol extracts of A. asiatica, P. oleracea and Trifolium repens L. Phytotoxic effects varied with extract solution, weed species and indicator plants employed, indicating that the weed species contained different contents and kinds of allelopathic chemicals. Water potential and pH adjusted to those of the extracts did not affect germination and seedling growth of the indicator plants. Phytotoxicity increased with increasing concentration of the extracts obtained from four suspected alleopathic weeds. Soil-incorporated plant residues of A. asiatica and P. oleracea caused greater phytotoxicity on radish than those of C. bursa-pastoris and T. repens.