In 2014 and 2015, USGA greens were established with creeping bent (CB) and annual meadow grass (AMG). One was built on the lysimeter facility at Landvik. In the acclimation period, half the green at Apelsvoll was shaded to about 30% of full sunlight. In autumn, the greens were fertilised weekly at decreasing rates with liquid fertiliser. Only nitrogen (N) and sulphur (S) varied among treatments. Other elements were given at rates which, according to the STERF fertiliser handbook, were adequate for the highest N rate. Total N rates September-November were 0/2.8/5.6/8.4 g/m2. The 5.6 g N/m2 rate was combined with either excess sulphur (N:S = 1:1.6) or no S, giving six treatments in total. Grass plants were sampled twice in winter and tested in the lab for freezing tolerance, resistance to pink snow mould and suffocation. Three rates of N were used in large-scale trials at Keilir GC (ISL), Roskilde GC (DK), Tapiola GC (FIN), Kungliga Drottningholm GC (SE) and Hauger GC (NO) in autumn 2016. Major findings:
• The highest N rate significantly increased microdochium patch in AMG and CB. The low N rate resulted in less microdochium patch, better colour and better reparation capacity in spring at Landvik compared with no-N and high-N
• The shaded green had significantly more disease and less freezing tolerance, but tolerance to suffocation was not affected
• Freezing tolerance of AMG was not significantly affected by autumn fertilisation. In CB there was a strong negative correlation between N rate and freezing tolerance • Four, 20 and 43% of the N given in autumn at a rate of 2.8, 5.6 and 8.4 g N/m2, respectively, was lost in drainage water.
• Sulphur generally had no effect on freezing tolerance or microdochium patch, except for Landvik where normal S gave less microdochium patch and better colour in AMG and CB compared with no-S and high-S. Exact autumn fertiliser guidelines are difficult because conditions vary between sites and years.
Based on our data, our recommendations are:
1. Use the same balanced mix of nutrients in autumn as in the rest of the year.
2. Adjust the N rate in late August to achieve normal harvest of clippings (a rate 20-30% lower than the maximum rate in June). Rough guidelines are 7, 5 and 3 kg N/ha/week in AMG, CB and red fescue, respectively.
3. Reduce fertiliser dose every week until the turf stops growing.
4. Reduce N rate by 10-20% if the risk of winter damage (e.g. shade, disease pressure, weak turfgrass species or varieties) is high.
