In 2014 and 2015, three USGA greens were established with creeping bent (Agrostis stolonifera) and annual meadowgrass (Poa annua). One of the experiments was conducted on the lysimeter facility at NIBIO Landvik. The other green was at NIBO Apelsvoll. During the acclimation period, half the green was shaded to about 70% of full sunlight. From the end of August until the end of November, the greens were fertilised weekly with liquid, complete, balanced fertilisers. Only the nitrogen and sulphate content varied between the treatments. The application rate declined weekly. The total nitrogen rate in the experimental periods was 0 / 2.8 / 5.6 /8.5 g N/m2. The 5.6 g/m2 rate was also combined with either an excessive rate of sulphate (N:S = 1:1.6) or no sulphate. Grass plants from the experimental greens were sampled in November/December and at the end of February and tested in the laboratory for freezing tolerance, resistance to pink snow mould and suffocation.
Some preliminary results: Nitrogen leakage: On average for two autumns, 40% of the high nitrogen rate and 20% of the middle nitrogen rate leached through drains. Drainage water was collected and analysed every two weeks. The highest nitrate concentration found was 14 mg/L. Leaching from zero-N plots was on average 0.5 g N/m2 and higher in the relatively dry autumn of 2015 than in the wet 2014.
Shade effects: The green in shade had significantly more disease and the average freezing tolerance (LT50 value) in December in both years was less than 50% of that in the plants exposed to full daylight. Shade strongly reduced the tiller density and survival in the field. There were no negative effects of shade on the tolerance to anoxia when M. nivale was controlled sufficiently in the autumn.
Excessive sulphate: High rates of sulphate did not reduce damage by M. nivale in field or laboratory tests.
Nitrogen rates in the autumn: High rates of nitrogen significantly increased the severity of M. nivale disease in annual meadowgrass and made creeping bent more vulnerable to pink snow mould. Freezing tests showed that annual meadowgrass was not significantly affected by autumn fertilisation. In creeping bent there was a strong negative correlation between nitrogen rate and LT50 value.
Colour and growth: Nitrogen application had a significant impact on height growth in the autumn. The zero-N plots did not have acceptable autumn colour and the growth was negligible. The highest nitrogen rate gave the best spring colour for creeping bent and the medium nitrogen rate gave the best colour for annual meadowgrass. Spring growth could not be predicted by the colour. Medium and high nitrogen rates both gave good spring growth in creeping bent. The low nitrogen rate gave best spring growth in annual meadowgrass.
Ongoing work: The optimal nitrogen rate for autumn fertilisation remains to be defined. Three nitrogen application rates were used in full-scale experiments at Keilir GC (ISL), Roskilde GC (DK), Tapiola GC (FIN), Kungliga Drottningholm GC (SE) and Hauger GC (NO) in autumn 20016, to obtain more data for the project.
