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Difficulties in obtaining successful establishment of birdsfoot trefoil (Lotus corniculatus L.) in sods of tall fescue (Festuca arundinacea Schreb.) cannot be fully explained by competition for water, nutrients, and light. The difficulty may be due to allelopathy that has been shown to exist in tall fescue. Laboratory and greenhouse experiments were conducted at Columbia, Mo., to characterize the influence of N fertilization and seasonal changes on the intensity of allelopathic effects of tall fescue on birdsfoot trefoil. Trefoil seeds were germinated in water extracts of fescue herbage (15 g herbage/100 ml H2O) applied to filter paper in a 23.3 C germination chamber and also in sand or soil (fine, montmorillonitic, mesic Udollic Ochraqualf) media in the greenhouse. Extracts of fresh herbage caused inhibition of germination and seedling growth, but ashing of the fresh herbage prior to extraction eliminated the inhibition. Previous N fertilization of tall fescue increased inhibition of germination and seedling growth. Percent germination and root and hypocotyl lengths of birdsfoot trefoil seedlings treated with the June through September extracts were 10, 13, and 7 times greater, respectively, than were those obtained from herbage sampled from January through May. Soil reduced the inhibitory effects of extracts, but root growth was still suppressed 54.7% in soil + extract as compared with the soil + water control. Growth of trefoil roots were reduced more by allelopathic substances than either germination or hypocotyl growth.

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In bio-assay procedures, aqueous leachates of tall fescue (Festuca arundinacea Schreb.) leaves and roots were shown to inhibit seedling growth of rape (Brassica nigra L.), birdsoot trefoil (Lotus corniculatus L. ) and red clover (Trifolium pratense L.). Genotypes of tall fescue varied in intensity of inhibition of other species, indicating that production of phytotoxic compounds may be genetically controlled.Tall fescue extracts were separated into anion, cation and neutral fractions.Inhibition was apparent mainly in the anion fraction. Substances in the anion fraction were identified with gas-liquid and paper chromatography as lactic, succinic, malic, citric, shikimic, glyceric, fumaric and quinic acids and several un knowns. uur researcn on aneiopatny in ta±JL rescue yr es uuca aiuiimiiauca Schreb.) was begun to determine if growth inhibitors were present, if tall fescue had an inhibitory effect on plants growing in asso ciation with it, and finally to identify the chemicals responsible for inhibition. Osvald CO in 1949, found that alcohol extracts of soil, on which red fescue (Festuca rubra L.) had been growing inhibited the germination of rape (Brassica nigra L. ) seed. Hoveland (2) in 1964, found that water extracts of dry ground roots of tall fescue had little effect on germination and seedling vigor of white (Trifolium rep ens L.), ball (T. nigrescens Viv.), crimson (T. incarna turn L.), and arrow leaf (T. vesiculosum Savi.) clovers.We began to explore the possibility of growth inhibitors in tall fescue because we noted that fields of tall fescue frequently had no other plant species growing with them. Toxicity of Tall Fescue Leachates to Rape (Brassica nigra L.) and Birdsfoot trefoil (Lotus corniculatus L.)Plants of Kentucky tall fescue were dug from the field in July, and the soil was washed from the roots. Tops and roots were separated

Tall fescue (Festuca arundinacea Schreb.) is known to inhibit the growth of birdsfoot trefoil (Lotus corniculatus L.) seedlings, but the inhibitors have not been identified. Our objectives were to characterize and identify these inhibitory substances. Water extracts of tall fescue herbage were fractionated into anion, cation, and neutral fractions. Paper and gas‐liquid chromatography were used to identify possible inhibitory substances. Birdsfoot trefoil germination and seedling development were inhibited mainly by the anion fraction. At pH 7.0, the anion fraction suppressed root growth by two‐thirds and hypocotyl growth by one‐halL Dilution of the total extract or its anion fraction to one‐third of its original concentration eliminated inhibition of germination, but not of hypocotyl and root growth. Root growth was inhibited more by the inhibitory substance(s) than either germination or hypocotyl growth. Concentration of extracts and low pH of the anion fraction were partial contributory factors to inhibition. Lactic, succinic, malic, citric, shikimic, glyceric, fumaric, and quinic acids plus several unknowns were identified as possible inhibitory substances. Lactic and succinic acids appeared as the major inhibitors.