Establishment Characteristics of Kentucky Bluegrass‐Perennial Ryegrass Turf Mixtures as Affected by Seeding Rate and Ratio1

Abstract Mixtures of grass species are desirable in a lawn for genetic diversity and to help ensure against establishment failures. Furthermore, it has been suggested that mixtures may potentially outperform monocultures of their components in terms of foliar density and possibly other factors. The purpose of this study was to determine the effects of various seed ratios (1:0, 3:1, 1:1, 1:3, 0:1) and rates (60 to 480 field‐viable seeds dm−2) of Kentucky bluegrass (Poa pratensis L., cv. Touchdown) and perennial ryegrass (Lolium perenne L., cv. Penfine) on leaf area index (LAI), shoot density, shoot size, species composition, ground cover, and clumping of the two grasses in the field. The treatments were based on field‐ viable‐seed ratios, which required data on the field survival, purity, and seeds g−1 of the seedlots. The soil was a Hagerstown silt loam (a fine, mixed, mesic Hapludalf). A shoot‐sizing technique was developed for the rapid measurement of LAI in turf stands. Using this method, results could be obtained with accuracy similar to direct area measurements but in less time. Mixtures tended to outperform monocultures by 8% in LAI, by 14% in shoot density (2 months after establishment), by 11 and 6% in foliar ground coverage (at 1.4 and 3 months, respectively), and by 44% in spring greening. A bluegrass ‐ ryegrass mixture containing 70 to 95% bluegrass field‐viable seeds provided the best compromise between adequate establishment of the bluegrass and minimal clumping of the ryegrass, which often occurs at low ryegrass seed densities. A seeding rate of 196 field‐viable seeds dm−2 produced a peak LAI value at 2 months after planting. No benefit was derived, in terms of leaf area, shoot density, or shoot size, from exceeding this rate. Low seeding rates of bluegrass and high rates of ryegrass tended to produce plants with the thinnest leaves during establishment. Shoot number, mass, and size of the two species were also affected by seeding rate and ratio.