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Agronomy Journal Abstract -

Effects to Turfgrass on the Establishment of Woody Plants1


This article in AJ

  1. Vol. 73 No. 4, p. 605-610
    Received: Mar 13, 1980

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  1. S. L. Fales and
  2. R. C. Wakefield2



Suppression of woody plants by grasses has been widely reported; but few studies have investigated the factors responsible for the reduced growth and poor appearance often shown by ornamental trees and shrubs planted in association with turfgrass. This research was undertaken to determine the major factors responsible for this phenomenon.

A field study, conducted over two growing seasons, evaluated the growth of flowering dogwood ( Cornus florida L.) and forsythia (Forsythia intermedia Spaeth.) planted in established sod (Enfield silt loam soil, Typic Dystrochrept). Treatments included different sized areas of turf-free space (0.3m2, 0.7m2, and 23.7m2), surface and subsurface placement of fertilizer and irrigation, and two mowing heights (10 cm and 4 an). Turfgrass significantly reduced the growth of both woody species. Although supplementary fertilizer, applied as a topdressing, failed to benefit the ornamentals, subsurface treatments resulted in considerable increases in growth. Competition for moisture did not appear to be responsible for the observed differences in growth, since maintaining a high level of soil moisture failed to overcome the inhibitory effects of the turfgrass. Competition for N, however, was indicated by results of leaf tissue analysis.

A bioassay experiment tested the hypothesis that the competitive nature of turfgrasses involves an allelopathic mechanism. Aqueous leachates of the roots of perennial ryegrass (Lolium perenne L.), red fescue (Festuca rubra L.), and Kentucky bluegrass (Poa pratensi L.) were applied to rooted cuttings of forsythia. Top growth of the forsythia was inhibited by leachates from all three turfgrass species. Root growth was suppressed by ryegrass and red fescue leachates.

Results of these experiments indicate that the suppression of woody plants by turfgrasses may involve chemical inhibition as well as direct competition for available N.

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