Cutting Height and Nitrogen Effects on Improved Perennial Ryegrasses in Monostand and Polystand Communities

New turf-type perennial ryegrasses are being widely used by turf managers, however, little information is available on their competitiveness in polystands. The growth and persistence of three perennial ryegrasses (Lolium perenne L.) were evaluated in the greenhouse and growth chamber in monostands and in polystands with ‘Merlon’ Kentucky bluegrass (Poa pratensis L.) and ‘Penncross’ creeping bentgrass (Agrostis palustris Huds.). Cutting height treatments were 1.26, 2.54, 3.80, and 5.08 cm. Ryegrass tillering was greatest at the 1.26 cm cut, while no differences in tiller numbers were detected between 2.54 to 5.08 cm treatments. All ryegrasses competed well in bluegrass sod at .2.54 to 5.08 cm cuts but did not grow well in the bentgrass, regardless of cut. In two field studies several ryegrasses were seeded 25: 75 (seed number basis) with Merlon Kentucky bluegrass and 50:50 with ‘Seaside’ creeping bentgrass. Mowing treatments and N treatments were imposed on the various mixtures in both studies. ‘Manhattan’ and ‘Pennfine’ ryegrasses were most competitive during establishment and the most persistent over 23 months in bluegrass mixtures. Shoot densities of the ryegrasses were not affected by cutting height or N treatments but bluegrass density was. When seeded with bentgrass, Manhattan and Pennfine were most competitive during establishment but noryegrass cultivar composed more than 14% of the stand after 23 months. Low cutting height (1.26 cm) and high N (2.44 kg N/100m²) improved the competitiveness of the bentgrass but not that of the ryegrasses. The data from these studies indicate that the competitiveness of new turf-type ryegrasses is dependent upon the companion grass. When seeded in mixtures with Kentucky bluegrass the new ryegrasses were persistent at cutting heights above 1.90 cm. In mixtures with creeping bentgrass the ryegrasses responded as temporary grasses.