Positive effects from late autumn fertilisation of turf grass, such as better winter colour and improved spring performance, have been reported from several studies in the US. However, applying fertiliser after growth cessation has not been common practice on golf greens in the Nordic countries.
The effects of mowing height in the autumn have not been well documented in previous studies. Increased mowing height on golf greens has been recommended by agronomists, but has not always been adopted in practice.
In autumn 2008, 18 experiments were established at golf courses in Finland (3), Sweden (3), Norway (11), and Iceland (1) with two mowing heights, 100% and 150% of normal height at the golf course. The greens were fertilised with a balanced, soluble fertiliser giving 0.2 kg N 100 m-2 when the turf had stopped growing.
The experiment was repeated during the winter 2009/2010. The winter injuries were different during these two winter seasons. The first winter was unstable, and ice cover caused severe injuries especially on annual meadowgrass (Poa annua L.) greens. The last winter was extraordinarily stable, with permanent snow cover for 2-3 months even in Denmark.
Different grass species were represented in the trials; creeping bentgrass (Agrostis stolonifera L.), red fescue (Festuca rubra L.), velvet bentgrass (Agrostis canina L.) and annual meadowgrass.
Turf cover (%) in the spring and general impression of turf quality were recorded in about 50% of the trials. Some observations of diseases and turf colour were also reported.
There were no or just small effects of different mowing heights. In red fescue we found a positive tendency on spring performance (p=0.10) from high mowing in one out of four trials.
There were no negative effects of late autumn fertilisation but significantly better spring performance in three out of four trials with red fescue. Two out of seven creeping bentgrass greens and one out of four velvet bentgrass greens also had significantly improved spring performance after late autumn fertilisation. The same tendency was observed in most of the other trials. Only two out of 20 greens with perennial grass species showed no effect of late autumn fertilisation.
Winter injuries were not significantly affected by late autumn fertilisation, but there were tendencies for better winter survival and less snow mould on some greens.
Annual meadowgrass greens were severely injured by anoxia in 2009 and by snow moulds in 2010. The trials provided no solid data for drawing conclusions concerning annual meadowgrass greens.
Due to the risk of nutrient leaching after late autumn fertilisation, further investigations should be done before compiling general recommendations. There are also reasons to conclude that enhanced applications of fertiliser throughout the autumn are preferable to one relatively large application of fertiliser in late autumn.
This project involved 16 greenkeepers as research technicians. They all started with high ambitions and set up the experiment according the protocol, but some lost their motivation when they either found the green 100% dead in the spring, or there were no obvious results from the experimental treatments. Five greenkeepers left their jobs during the project period. Extraordinary early snow cover left some greens untreated. Additional treatments (private experiments) made interpretation of the data difficult. Finally a set of data was lost in the mailing system. However, some greenkeepers carried out the experiment and reported reliable data on time.
Involving greenkeepers in a project like this makes it possible to run an extended number of experiments and it creates a positive involvement, but collecting and interpreting data became a challenging task.