Allelopathic Effects of Tall Fescue Genotypes1

Abstract

AbstractTall fescue (Festuca arundinacea Schreb.) has been shown to have allelopathic effects on some species. Some tall fescue genotypes growing in a breeding nursery had large crabgrass [Digitaria sanguinalis (L.) Scop.] infestations while other genotypes had none. The difference in infestations did not appear to be due to competition; therefore, the possibilities of allelopathic effects were investigated. The surface 2.5 cm of soil in which the various tall fescue genotypes were growing was placed in pots in the greenhouse. The crabgrass germination in the greenhouse varied with genotypes in a manner similar to what had been observed in the field. Genotypes were evaluated for allelopathic effects by germinating seeds of birdsfoot trefoil (Lotus corniculatus L.) and medium red clover (Trifolium pratense L.) in petri dishes containing extracts made by soaking 10 g of tall fescue leaves in 100 ml of water for 24 hours. After 10 days, germination of the legume seeds was significantly inhibited by fescue extracts as compared with distilled water. After 14 days, one tall fescue genotypes had significantly less germination of birdsfoot trefoil seed than did three other genotypes, while one genotype had significantly less germination of red clover seed than did one other genotype.Birdsfoot trefoil and red clover seedlings were grown in half‐strength Hoagland's solution containing extracts of three tall fescue genotypes made by soaking 3, 5, and 10 g of tall fescue tissue for 24 hours in distilled water. Roots of birdsfoot trefoil were significantly inhibited by the 10‐g concentration as compared with the 3‐g concentration in two out of three genotypes. The 10 gm concentration of one genotype significantly inhibited shoot growth of birdsfoot trefoil as compared with the 3‐ and 5‐g concentrations. Shoot and root growth of red clover were significantly inhibited by all extracts of tall fescue genotypes. In extracts of two out of three genotypes, the 10‐g concentration significantly reduced the top growth of red clover. Soils on which three fescue genotypes had been grown were incubated in the greenhouse for 0, 1, and 2 weeks and birdsfoot trefoil seedlings were planted into them and in soil that was not exposed to tall fescue. Root and shoot growth of birdsfoot trefoil seedlings was significantly inhibited when grown in soils in which fescue genotypes had been grown, but incubation periods of the soil had no effects. In soil from one genotype, root and shoot growth of red clover were significantly inhibited when unincubated and inhibition decreased when the soil had been incubated for 2 weeks. In soil from another genotype, root and shoot growth of red clover were significantly inhibited in all incubated soils as compared with the check soil. In soil from the third genotype, root and shoot growth of red clover were inhibited at all incubation periods, but inhibition of shoot growth was greater in soil incubated for 2 weeks as compared with 0 weeks.