Performance of Kentucky Bluegrass and Bermudagrass Mixtures in a Transition Zone Environment.

The use of warm-season turf species, such as bermudagrass [Cynodon dactylon (L.) Pers.] and zoysiagrass (Zoysia spp.), has been recently promoted in the transitional zones of Europe to reduce water consumption for irrigation. However, turf managers and home lawn owners are often discouraged from using these species because they undergo dormancy during winter and lose color up to five months. These issues may be addressed by mixing cool-season species together with warm-season turfgrasses. In the resulting mixture, cool-season species should be dominant during winter while the warm-season species should be prevalent in summer. However, there is a lack of information on performances and dynamics of species succession of cool- and warm-season grasses mixtures. Therefore, a 2-yr study was carried out at Padova University (northeastern Italy) to test the turf quality and species succession of various kentucky bluegrass (Poa pratensis L.) and bermudagrass mixtures. Bermudagrass cultivars Veracruz and Yukon were seeded in June 2011 at a 5 g m^-2 rate and overseeded in September 2011 with kentucky bluegrass cultivars Brooklawn, Mystere, and Nublue Plus at a 30 g m^-2 rate. Plots (3 × 2 m) were fertilized in September, October, and March using urea at 20 g m^-2 yr^-1, and were mowed weekly at a 30-mm height. Visual turf quality was estimated every other week using a 1–9 scale, with 1 = dead, 6 = acceptable, and 9 = optimal. Every month, the frequencies of mixture-species were determined using linear transects, by recording species in 10-cm segments of four lines of 1 m each. Regardless of the kentucky bluegrass cultivar used, mixtures including bermudagrass Veracruz had higher visual quality in the fall and winter compared to those including Yukon. Species succession was influenced by bermudagrass cultivars, while kentucky bluegrass cultivars had no effects on the rate of change of plant composition. The results of this study suggest that the choice of bermudagrass cultivar plays a key role for establishing functional kentucky bluegrass and bermudagrass mixtures in northern Italy.