Cultivar composition and spatial patterns in Kentucky bluegrass blends

Turfgrass managers make informed decisions when choosing cultivars, but they do not know the cultivar composition or spatial patterns of a blended Kentucky bluegrass (Poa pratensis L.) stand after establishment. This study was conducted to determine the cultivar composition of blends and determine whether cultivars form distinct clumps or a random distribution. Percentages of Blacksburg', Midnight', and 'Unique' in blends were determined using random amplified polymorphic DNA markers. The two different locations were a fairway (Aspen Ridge Golf Course, Bourbonnais, IL) and a rough (Alpine Hills Golf Course, Rockford, IL). Indices of dispersion were used to determine spatial patterns. Even though the two stands had different management strategies and were 157 km apart, the two blends had similar cultivar compositions in October 2000. The fairway was comprised of 14% Blacksburg, 46% Midnight, and 40% (w/w) Unique 37 mo after seeding, while the rough composition was 14% Blacksburg, 47% Midnight, and 39% (w/w) Unique 15 mo after seeding. Chi-square analyses indicated with more than 99% confidence that the cultivar compositions were different than the intended planting. Comparing expected (first sampling) with observed (second sampling) values at both sites, chi-square analyses determined that none of the mean percentages for the three cultivars had changed from the first sampling date to the second at either location. Since the two stands were not the same age, they may have achieved an equilibrated composition dictated by the competitve advantages of the component cultivars. Indices of dispersion determined the cultivars were distributed randomly rather than clumped. This study suggests management and location do not dictate the composition of a blend. Rather, the competitive advantages of the cultivars in the blend will determine composition.