Growing quality turfgrass throughout the year in the transition zone is difficult. The transition zone is identified as the area of transition from cool- to warm-season turfgrasses between the cool and warm regions of the world (Beard, 1973). Traditionally, the main turfgrasses grown in the transition zone are zoysiagrass (Zoysia japonica Steud.), bermudagrass [Cynodon dactylon (L.) Pers.], Kentucky bluegrass (Poa pratensis L.), and tall fescue (Festuca arundinacea Schreb.) (Beard, 1973). Zoysiagrass and bermudagrass can successfully be grown in the transition zone; however, winter dormancy and occasional winter kill cause unsightly appearances in the winter and early spring (Munshaw et al., 2004). Kentucky bluegrass and tall fescue can be grown in the transition zone, but high humidity, high temperatures, and droughty soil conditions associated with summer months are often too stressful for Kentucky bluegrass and tall fescue to thrive under these conditions. Diseases such as rust (Puccinia graminis Persoon subsp. graminicola Urban) and dollar spot (Sclerotinia homoeocarpa Bennett) in Kentucky bluegrass and brown patch [Rhizoctonia solani (Kühn)] in tall fescue can occur under these stressful conditions (Landshchoot and Park, 1997; Wang and Huang, 2004).
Alternatives to bermudagrass, zoysiagrass, Kentucky bluegrass, and tall fescue are new interspecific hybrid bluegrass varieties (Poa arachnifera Torr. × P. pratensis L.) (Registered with the USDA as Kentucky bluegrass cultivars; however, for the ease of discussion they will be called hybrid bluegrass). Two varieties, ‘Dura Blue’ and ‘Thermal Blue’, have recently been released by The Scotts Company (Marysville, Ohio). Traditionally, Kentucky bluegrass has not been the turfgrass variety of choice in the southern part of the transition zone due to its lack of heat, drought, and disease tolerance. Hybrid bluegrass has displayed the heat and drought tolerance of Texas bluegrass (P. arachnifera Torr.) and the desirable turfgrass quality and color of Kentucky bluegrass (Abraham et al., 2004). However, the same diseases (leaf spot, leaf rust, dollar spot, etc.) are still concerns with hybrid bluegrass. The extent of the susceptibility to these diseases is not known for these varieties.
Kentucky bluegrass fertility and management are different from tall fescue. Kentucky bluegrass nitrogen (N) fertilization ranges from 19 to 64 kg·ha−1 per month depending on variety (Beard, 1973). Kentucky bluegrass may have increased incidence of dollar spot and leaf rust when managed with low N levels. Tall fescue N fertilization ranges from 19 to 50 kg·ha−1 per month (Beard, 1973). Brown patch is a problem in tall fescue during summer heat stress, and increased levels of brown patch may occur with excess N fertilization (Christians, 1998).
One consideration with the introduction of new turfgrass varieties such as ‘Dura Blue’ and ‘Thermal Blue’ is determining whether these varieties are better suited for establishment and use than traditional species. The objectives of this experiment were to determine if N levels affected turfgrass color, quality, clipping yield, and disease incidence of ‘Apollo’ Kentucky bluegrass, ‘Dura Blue’ and ‘Thermal Blue’ hybrid bluegrass, and ‘Dynasty’ and ‘Kentucky 31’ tall fescue.
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Kopp, K.L. & Guillard, K. 2002 Clipping management and nitrogen fertilization of turfgrass: growth, nitrogen utilization, and quality Crop Sci. 42 1225 1231
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Miltner, E.D., Stahnke, G.K., Johnston, W.J. & Golob, C.T. 2004 Late fall and winter nitrogen fertilization of turfgrass in two pacific northwest climates HortScience 39 1745 1749
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