Evaluating Kentucky bluegrass and perennial ryegrass seeding ratios for sod grown on plastic production

Abstract Sod grown on plastic (SOP) is a sod established on a thin layer of growing medium atop a plastic sheet. It can be harvested with minimal damage to the roots, thereby reducing transplant shock. Kentucky bluegrass (KBG; Poa pratensis L.) is a commonly used cool‐season turfgrass species in sod production and sports fields. However, KBG is slow to germinate, which can leave the initial stages of SOP production vulnerable to erosion and increased production time. We hypothesized that incorporating perennial ryegrass (PRG; Lolium perenne L.)—a faster‐germinating species—could help stabilize the growing medium until KBG germinates. Thus, the objective of this study was to evaluate the establishment and strength of cool‐season SOP seeded with varying KBG and PRG seeding ratios. This study was conducted at the Hancock Turfgrass Research Center in East Lansing, MI, in June–October 2023, and May–September 2024. Six KBG‐PRG seeding ratios based on seed count (100:0, 98:2, 96:4, 92:8, 84:16, and 0:100) were evaluated. The addition of 16% PRG resulted in a 58% increase in tensile strength compared with the 100:0 ratio and resulted in a 56:44 KBG‐to‐PRG shoot ratio.