KENTUCKY BLUEGRASSES FOR TURF

The performance of Kentucky bluegrass (Poa pratensis) as a turfgrass in Kansas concerns many growers. In some situations bluegrass has produced a high quality, excellent turf for many years; in other instances growers have had problems maintaining an acceptable turf. One reason for poor performance is that Kentucky bluegrass, a cool season turf, is best adapted to cool, humid environments. Kansas, in the transition zone between cool and warm climates, is at the southern area of adaptation for bluegrasses. Thus, the high-temperature and drought stresses could cause the grass, particularly under improper maintenance, to decline in quality. Another major reason for variability in performance is that cu ltivars differ. Many cultivars of Kentucky bluegrass are available and new ones continue to be developed. Cultivars differ greatly with respect to environmental and pest tolerances. Also, fertilization and irrigation requirements differ. If the proper bluegrass cultivar is not selected for a particular site, inferior performance may result; a cultivar better adapted to the site, however, might grow very well. Several factors

should be considered when recommending which particular bluegrass cultivar to use: quality desired, maintenance level, shade level, mowing height, possibility of iron deficiency, and pests.
Cultivars have been evaluated at two Kansas sites: the Horticulture Research Center near Wichita and the Rocky Ford Turf Area near Manhattan.Wichita, in USDA hardiness zone 6, has a fine sandy loam soil (pH 6.5-6.8);Manhattan, in hardiness zone 5, has a silty clay loam soil (pH 7.1 -7.4).Trials were conducted under both medium to high maintenance and low maintenance conditions.Visual quality ratings for a 6-year period (Table 1) revealed very good performance for Sodco, Victa, Majestic, Windsor, and Baron.Cultivars that rated low tended to be common-type bluegrasses.The 1978 ratings reflected a year of considerable drought stress on the turfgrasses.
for Kentucky bluegrass cultivars, Wichita, 1973Wichita, to 1978. 6 . 6   All the cultivars were susceptible to at least one major turfgrass disease (Table 1 ).Fusarium blight and stripe smut are considered particularly deterimental diseases on bluegrasses.
Vigorous, improved cu ltivars selected for medium to high maintenance may produce ex• cessive thatch, which over a period of time cou ld cause turf deteriorat ion f rom poor rooting, drought and high temperature stresses, diseases, and in• sects.In this trial, these cult ivars exhibited excess ive thatch accumulation after 6 years: Victa, Sydsport, Baron, and Bonnieblue.They may require thatch control measures.6.9 5.7 6.9 6.3 6.7 5.3 6.5 4.7 6.5 6.7 6.5 4.6 6.4 6.3 6.4 6.0 6.3 4.3 6.1 6.7 6.1 4.7 6.1 6.3 5.9 5.0 5.8 6.0 5.7 5.0 5.6 3.7 5.4 5.7 5.0 4.3 5.0 Observing data in Tables 2 and 3 reveal how maintenance can influence turfgrass performance.All cultivars grew better under 5.0 lb N/1000 sq.ft./yr.Evidently the extra N in the summer was beneficial on the light, sandy soil where frequent irrigation was necessary to reduce summer stresses.Under the 2.5 inch height, turf quality was higher than the 1.0 inch.The lower N-rate combined with the 1.0-inch cutting height resulted in the lowest qualities of turf.
Manhattan Trial 1976 to 1980.In September 1976 a trial contain ing 38 cultivars was established under 3.0 lb N/1000 sq.ft./yr.Due to the heavier and more fertile soil, this N-level would be considered a medium to high level.Clippings were returned after mowing and irrigation were applied t o avoid excessive stress.Cutting heights were 1.0 (recreational turf) and 2.0 inches (home lawns).
In general the bluegrasses produced a better quality turf under the 2.0-inch than the 1.0-inch mowing (Table 4).At 2.0 inches, perform ance was outstanding for Ram I, Adelphi, K3-170, Glade, and Sydsport.Several others had very good quality.When maintained at a 1.0-inch height, Adelphi, and K3-179 were outstanding and several other cultivars rated very good.
Whenever a substantial disease infestation occurred, the plots were rated (Table 5).These cultivars exhibited moderate or greater disease susceptibility for at least one rating period: Cultivars with moderate or greater susceptibility to dollar spot, leaf spot, Fusarium blight, or stripe smut should be avoided in bluegrass monostands or blends.These are serious diseases on Kentucky bluegrasses in Kansas.Stem rust is less serious than the other diseases and can normally be corrected with adequate nitrogen.

Low Maintenance
Jn some situations, growers desire a low maintenance turf that requires infrequent mowing, very I ittle fertilization, and limited irrigation.Even so, growers still want a certain quality of turf.In the past most breeding and selection of bluegrasses were for medium to high maintenance conditions. 1 n recent years, however, low maintenance adaptation has received attention.
In a trial of 32 cultivars, established at Manhattan in March 1977, each c ultivar was evaluated under cutting heights of 1.0 and 2.0 inches.Fertilization was at 0.75 lb N/1000 sq.ft./yr., applied in early fall.Turf was irrigated only for survival; for example, in the hot, dry summer of 1980 the area was irrigated with 1.5 inches of water.Clippings were returned and a preemergence crabgrass herbicide was applied each spring.Selection of cultivars for this trial was based on information from breeders that a cultivar had potent ial for low maintenance condit ions.
q ua lity ratings at the 2.0-inch than at t he 1 .0inch Du ring the first year, grasses t hat respond to highe r mowing height ( exhibited acceptable quality; under 1.0 inch, only Arboretum and Park were acceptable.Certain cultivars, such as Adelphi, Touchdown, and Sydsport, that rate very high under medium to high maintenance, perform poorly under low maintenance.These cultivars were bred and selected specifically for higher maintenance.On the other hand "common-type" cultivars, such as Park, may do well under low maintenance but deteriorate under high maintenance.Thus, among bluegrass cu ltivars, performance varies greatly under different cultural regimes.
In the fall of 1977 disease activity was noted on the plots.These cultivars exhibited moderate-tosevere diseases:

Summary
Kentucky bluegrass cultivars evaluated at Wichita and Manhattan from 1973 to 1980 differed greatly in performance.Under medium to high maintenance these cultivars rated very good (visual quality of 7.6 or above) at one or both locations: Adelphi, Baron, Fylking, Glade, Ram I, Sodco, Sydsport and Touchdown.However, since no Kentucky bluegrass is completely resistant to all diseases, these bluegrasses would best be used in a blend of 2 to 4 cultivars.Under low maintenance the acceptable cultivars were Arboretum, Baron, Merion and Park.
Further cultivar evaluations are being conducted at both sites with 40 to 60 cultivars.Based on two years' data from these trials, several other Kentucky bluegrasses have good potential for Kansas.

Table 1 .
Visual quality, disease, and thatch accumulation

Table 2 .
Performance of Kentucky bluegrass varieties,

Table 3 .
Performance of bluegrass varieties, mowed at 1975 to 1980.