Hybrid bluegrass, Kentucky bluegrass, and tall fescue response to nitrogen fertilization in the transition zone

'Dura Blue' and 'Thermal Blue' hybrid bluegrass have been selected for heat and drought tolerance. These grasses offer alternatives to traditional Kentucky bluegrass and tall fescue in the transition zone. Experiments were conducted in two locations during 2003 and 2004 at the University of Tennessee in Knoxville, Tenn. Nitrogen (N) was applied at 50,150, or 300 kg center dot ha(-1) N per year to 'Apollo' Kentucky bluegrass,'Dura Blue', and 'Thermal Blue' hybrid bluegrass, and 'Dynasty' and 'Kentucky 31' tall fescue. The main effects of turfgrass and N were significant for color and quality observations. However, their interactions were not significant; therefore, only the main effects are shown. Acceptable turfgrass color (> 6) and quality (> 6) was observed for all varieties in May, August, and November. All N regimens showed acceptable turfgrass color and quality. However, 150 kg center dot ha(-1) N per year was required to achieve optimum color and quality. 'Kentucky 31' produced higher clipping dry weights when N was applied at 50 kg center dot ha(-1) per year than the other varieties. Nitrogen applied at 150 and 300 kg center dot ha(-1) per year on 'Kentucky 31' and 'Thermal Blue' produced higher clipping dry weights than the other varieties. 'Dynasty' and 'Kentucky 31' had similar brown patch incidences at each nitrogen level. Increases in brown patch incidence occurred as N levels decreased from 300 (21%) to 50 kg center dot ha(-1) per year (31%) for 'Dynasty' and 'Kentucky 31'. Dollar spot incidence occurred on all bluegrass varieties from 7% to 24%. However, dollar spoil decreased with increased N fertility. All turfgrass species tested were acceptable for use in the transition zone.