Laboratory and glasshouse studies were conducted to assess the allelopathic effect ofChenopodium albumL. on the germination and early growth of certain crop species. Test species were grown in soils containing 1 (m/m) freeze-dried shoot material of the weed. Aqueous extracts of soils containing weed residues and organic solvent extracts of shoots of the weed were tested for effects on the germination of certain crop species. Radish (Raphanus sativusL.) was the only crop not affected by the weed residue in the soil. Growth inhibition was 68 for cucumber (Cucumis sativusL.), 85 for onion (Allium cepaL.), 47 for tomato (Lycopersicon esculentumL.) and 51 for sunflower (Helianthus annuusL.). Except for radish and sunflower, stand loss contributed to reductions in growth. Germination of crop species was not affected by aqueous extracts of soil portions (100g) from soil either grown with the weed (residues later removed by sieving) or containing shoot material of the weed. In fact, the growth of radicles of certain species was stimulated in the latter extract. The ethyl acetate, 100 and 50 methanol extractable fractions ofC. albumshoots inhibited germination of the single test plant (onion). The hexane extractable compounds slightly retarded germination. It is suggested thatC. albumcontains allelochemicals which may inhibit seed germination and growth of certain crop seedlings.
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