All experiments in ICE-BREAKER were completed in 2023 and results were presented at a final seminar in Oslo on 3 November. STERF and the Research Council of Norway have granted an extension of the project until 31 May 2024 for remaining publications to be completed. The 10 main conclusions from the project are that:
1. Ice and water damage in future winter climates will probably be caused by meltwater and repeated freeze/thaw rather than anoxia, but long winters with anoxia may occur every 5-10 years.
2. Because of this, the need for properly designed and well-drained greens and green areas will become even more important in the future.
3. We recommend coverage with a tarp + plastic to prevent ice and water damage.
Ventilation under the covers is needed as insurance in years with a long winter, especially on Poa greens.
4. Plastic covers neither increase nor decrease the need for fungicide applications in autumn.
5. Poa is by far the least winter-hardy species on Nordic putting greens. New varieties of chewings fescue from Northern Europe may be at least as tolerant to ice encasement as new varieties of creeping bentgrass from USA.
6. All species, and especially Poa, may suffer from photoinhibition after release from ice encasement and/or plastic covers in spring. We recommend not exposing turf to intense sunlight after being covered through the winter; risk of damage can be decreased by removing plastic on a cloudy day.
7. Fast re-establishment of winter-killed greens from seed in spring is primarily a question of soil temperature, adequate water supply, good seed-soil contact, sufficient phosphorus supply and ample nitrogen supply.
8. Creeping bentgrass varieties differ in their 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 most slowly germinating varieties, such as ‘Independence’ and ‘Memorial’, should be avoided.
9. Spring covers are important to accelerate germination and seedling growth after reseeding in spring. Their effect is primarily due to higher soil temperature, but they also protect against hard rains, desiccation and high light intensity.
10. Growth-inhibiting concentrations of butyric or acetic acid or other compounds were not detected in winter-killed greens after up to 115 days of ice encasement. Since these acids are volatile and tend to evaporate in a few days, their role in inhibiting germination and seedling growth after ice encasement may have been overrated in the past.
