A summary from the final seminar in Oslo, Norway
by Sigridur Dalmannsdottir, Karin Juul Hesselsøe and Trygve Aamlid; NIBIO Turfgrass Research Group, Norway
Climate change, with more unstable winter weather, increases the risk for turfgrass damage due to ice encasement and recurring freeze/thaw cycles on golf courses in the Nordic countries and in other areas that in the past had stable snow cover. Ice damage in future winter climates in the Nordic countries will most likely be more related to melt water and repeated freeze/thaw than to lack of oxygen (anoxia). Nonetheless, we must be prepared for long winters with anoxia every 5-10 years. The years 2013, 2018 and 2023 had winters which caused severe ice damage in the Nordic countries. Figure 1 shows damages on a green in northern Norway.
The ‘ICEBREAKER’ project was initiated in 2020 with the objective to reduce agronomic and economic impact of ice damage on golf courses and other grasslands. In the beginning of November about 80 attendees took part in the final seminar of the “ICEBREAKER” project held in Oslo, Norway. These included golf course superintendents, researchers and others working with, or interested in, golf courses. Researchers from Norway (NIBIO) and USA (University of Minnesota and University of Massachusetts), golf courses and golf federations from Norway and Sweden and industry partners (7Sense) have been involved in the project.
Read more about the program of the seminar and the presentations on the STERF website.
Pål Melbye from the Norwegian Golf Federation and the project leader opened the seminar. Invited speakers Hans Olav Hygen from the Norwegian Meteorological Institute presented future climate scenarios and Emily Merewitz Holm from Michigan State University presented how the sensitivity of the crown structure can lead to winter kill. Most of the project participants presented work from the different work objectives: Trygve Aamlid, Sigridur Dalmannsdottir, Håkan Blusi, Mads Thers, John Riiber/Albert Holmgeirsson, Wendy Waalen, Karin J. Hesselsøe, Pia Heltoft, Marit Almvik and Carl Johan Lønnberg (Figure 2).
Species selection
The project confirmed that Poa annua is by far the least winter hardy species on Nordic putting greens. New varieties of Chewings fescue from North Europe, including Norway, may be at least as tolerant to ice encasement as the new varieties of creeping bentgrass from the USA. The velvet bentgrass variety ‘Nordlys’ had the highest tolerance against ice encasement and anoxic situations in our experiments. However, more reliable methods need to be evolved for screening species and varieties for ice and water tolerance under typical field conditions.
Winter plastic covers
The results from the project indicate that proper coverage with plastic and an undercover can drastically reduce damage from ice and water (Figure 3). Ventilation under the covers is needed as an insurance in years with a long winter, especially on Poa-dominated greens. The need for properly designed and well-drained greens and green areas will become even more important in years to come. Plastic coverage neither increases nor decreases the need for preventative fungicide applications in autumn.
Re-establishment of greens
Fast re-establishment of winter-killed greens from seed in spring is primarily a question about soil temperature, adequate water supply, good seed-soil contact, sufficient supply of P and ample supply of N. There are differences among creeping bentgrass varieties in ability to re-establish at low soil temperatures, but these differences also depend on the seed lot used and are altogether less important than the varieties’ overall turfgrass quality over several years. The slowest germinating varieties such as ‘Independence’ and ‘Memorial’ should be avoided.
Successful germination in the spring
Spring covers are important to accelerate germination and seedling growth after reseeding in spring. Their effect can primarily be attributed to soil temperature, but they also have a role as protectants against hard rains, desiccation, and high light intensities after seedling emergence.
Growth-inhibiting concentrations of potentially toxic compounds, such as butyric or acetic acid, were not detected in soil water from winter-killed greens after 115 days of ice encasement in 2022 (Figure 4).
We don’t know how this would have been after 150 days of ice encasement like in 2023, but since butyric and acetic acid are volatile compounds that tend to evaporate or get degraded by microbial activity in the soil, their role in inhibiting germination and seedling growth after ice encasement may well have been overrated in the past.
Oxidative stress in the spring
All species, and especially Poa annua, may suffer from oxidative stress/photoinhibition after release from ice encasement and/or plastic coverage in spring. We recommend removing the plastic winter cover on a cloudy day. Further research into the use of temporary shade covers and/or turf colorants is needed.
The ‘ICEBREAKER’-seminar was moderated by Director of the Scandinavian Turfgrass Environmental Research Foundation (STERF) Maria Strandberg (Figure 5). The project was funded by both STERF and Research Council of Norway.
