Technical
The conclusions were that the fine grass greens were consistently smoother, truer and faster than annual meadow-grass greens, and that the fine grass greens were not as prone to seasonal inconsistency for these measured parameters
” Graph showing the relationship between surface hardness and volumetric soil moisture content
grass may simply be tolerant of a wide spectrum of surfaces, though the proportion of annual meadow-grass to the softer, wetter fine grass dominated greens may be relatively high - though not 50% or more!
surface performance for golfers without adding to turf stress
So, if we want to give golfers consistent surfaces year-round, then we should favour the fine grass. However, the measurements that I feel are the most interesting, and which contribute immensely to consistent year-round performance, are those for surface hardness and volumetric soil moisture content (VSMC), which are shown on the accompanying graph. These are the data sets that I will focus on for the remainder of this article.
Only hard and dry for fescue/bent?
The most obvious statement from the data represented in the graph is that fine grass is favoured by harder and drier conditions, annual meadow-grass by softer, wetter ground. As with all relationships, it is not as simple as this, with both types of turf appearing in each other’s dominant territory. This may well be down to site conditions, with annual meadow- grass tolerating harder, drier situations such as links or USGA Recommendation greens. Fine
Practices such as rolling can improve
When considering which grasses your course should favour, don’t simply make a decision based on green or blue dots on a graph. Neither should we confine our ambition to the belief that fescue/bent is for links and annual meadow-grass is for parkland. Target ranges for hardness are 100-150 Gravities for links and 85- 110 for parkland greens. The ranges for soil moisture content are 10-25% for links and 15- 30% for parkland. Another look at the graph shows that there are a lot of fine grass greens within the parkland target ranges. The inference is that you can have playable parkland greens with fine grass, and that you do not need to aim for unrealistic levels of hardness to achieve fine grass greens.
There are a number of caveats when considering the type of green and grass your course is capable of supporting and, amongst them, is design. Parkland courses not designed for the running game should not implement the STRI’s target range for links, perhaps not even the higher end of the range for parkland. Shade will also affect which grasses you can grow - with a browntop bent dominant sward (only requiring 50% or over, remember) possibly being as good as it can get. The key to producing consistency will be to achieve a true blend of grasses.
More questions than answers?
The data on hardness and volumetric soil moisture content does raise a number of questions, which include:
- Are the annual meadow-grass greens to the left of the graph (say >90 Gravities and <25% VSMC) prime for conversion to bent/fescue, with the possibility of limited disruption to the quality of playing surface through the process?
- What level of resources is required to produce annual meadow-grass greens above 100 Gravities? I would suggest that these are out of their natural comfort zone and require the full tool kit available to greenkeepers, including plant growth regulators, enough fertiliser and water to minimise stress, fungicides, lots of sand topdressing, etc. However, they could also, sadly, be poorly managed links/heathland greens; a clear opportunity for conversion to bent/fescue.
- What might happen to such greens when the greenkeeper loses the spanner or hammer from their tool kit?
- What sort of surfaces are greenkeepers presenting at VSMCs over 30%? The USGA “Recommendations for a Method of Putting Green Construction” specify that the rootzone should have a total porosity of 35- 55%, which they define as “the degree to which the soil mass is permeated with pores or cavities”. If water is filling much of this space, as it has to be to a number of greens
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