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Book: Proceedings of the Second International Turfgrass Research Conference
Published by: American Society of Agronomy, Crop Science Society of America



  1.  p. 104-111
    Proceedings of the Second International Turfgrass Research Conference

    Eliot C. Roberts (ed.)

    ISBN: 978-0-89118-573-4




Influence of nitrogen fertilization on species dominance in turfgrass mixtures1

  1. R. E. Engel


Influence of nitrogen fertilization on increase or decrease of individual species composing turfgrass mixtures is of continuing concern to the turf manager. When such population shifts occur, total growth response to N is considered part of the mechanism. Also, N has indirect effects that influence a plant's competitiveness. Disease susceptibility, drought tolerance, and temperature tolerances are good examples. In some of these situations with most severe conditions, sudden kill of a turfgrass species can occur. At such time, survival of one of the competitive species gives a sudden and large shift in turfgrass species composition.

The amount of N fertilizer applied, the season of N application, the season N becomes available from the soil, and various forms of N carriers are expected to produce slow shifts in grass population on turf sites. The degree of species change should vary with the aggregate of dissimilarities of the competing species that effect the N response. Kentucky bluegrass-bentgrass and bentgrass-annual bluegrass mixtures which are rather similar in temperature and moisture requirements do not show a great shift toward complete dominance of one species with varied N use. Major shifts in turfgrass population from N fertilization developed with a mixture of zoysiagrass (Zoysia japonica Steud.) and Kentucky bluegrass (Poa pratensis L.). A good supply of available N is expected to favor the more aggressive, weedy, or colonizing grasses.

Nitrogen fertilization has an important influence on turfgrass species populations in a mixture. The potential of this influence from N fertilization will vary with temperature and moisture. In most cases shifts in species content of mixed turf will occur rather slowly and subtly. As turfgrass production becomes more efficient and single species or cultivars are grown, the influence of N fertilization on species population changes will need more study. Additional index words: Turfgrass mixtures, Nitrogen fertilization, Kentucky bluegrass, Red fescue, Annual bluegrass, Bermudagrass, Zoysiagrass, Bentgrass, Turfgrass species balance, Growth temperature limits, Zoysia japonica Steud., Poa pratensis L.

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Copyright © 1974. Copyright 1974 by the American Society of Agronomy, Inc. and the Crop Science Society of America, Inc., 5585 Guilford Rd., Madison, WI 53711 USA