Poa pratensisorLolium perennefor establishment and overseeding of Scandinavian football (soccer) pitches

Scandinavian football pitches are sometimes sodded because of slow establishment of Kentucky bluegrass (KB, Poa pratensis) from seed. Sodding is fast but expensive and brings with it thatch and sometimes annual bluegrass (AB, Poa annua). Perennial ryegrass (PR, Lolium perenne) is used for overseeding and often becomes an important component of the turf. Triggered by experiences in SW Norway and predictions for milder winters, our objectives were (1) to compare KB sod and PR seed for establishment of football pitches in three climatic regions; and (2) for both types of turf to document the effect of overseeding PR or KB in spring, summer or fall on turf cover, botanical composition, and wear tolerance. Field trials with sodded KB and seeded PR on main plots and overseeding on subplots were conducted from June 2008 to Nov. 2011 at the Bioforsk units Landvik (58 °N, coast), Apelsvoll (61 °N, inland) and Kvithamar (64 °N, coast). Seeded PR plots could be opened to play one month after sodded KB plots. KB survived well at all sites, but complete winterkill of PR occurred in two out of three years at Kvithamar and one out of three years at Apelsvoll. At Landvik one of two main plots with PR died during the last winter. The fact that winterkill was not caused by snow mold but long-lasting ice covers or low freezing temperatures combined with little or no snow cover, shows that a milder but more unstable winter climate will not allow for pure PR pitches in the future. Pitches still ought to have KB in the base, but PR is recommended for overseeding, preferably in spring, to reduce AB ingress and improve turf quality. Overseeding of PR into KB did not outcompete KB, but overseeding of KB into PR or KB was mostly not successful.