Greens

Current Conditions

Over the course of the last 10 years, percentages of Poa annua and Couch Grass encroachment have gone beyond the levels where sustainable control options are viable without severely compromising the playability of the Greens surfaces. Management is now centred around the suppression of Poa annua and Couch, to give the bentgrass a competitive advantage and to provide a somewhat compromised putting surface.

Depending on the level of infestation, the suppression of Poa annua and Couch grass can, over some greens, present a “bumpy” uneven surface which is to the detriment of putting conditions. With the varying levels of Poa annua and Couch grass across the course greens in general, this leads to inconsistency in presentation that we currently experience.

Couch grass, particularly in summer where its growth rate is at its highest, has over time invaded through the greens collars and into the putting surfaces.  Most greens at Glenelg do not have a defined collar with Couch now the dominant specie. The collar of the green should act as a buffer against encroachment, however with the level of infestation, the only control option available is to apply non-selective herbicide and physically dig the Couch roots out.

As a green surface ages, it accumulates a layer of thatch immediately below the surface. Consisting of organic matter at varying stages of decomposition, the thatch layer poses a varying range of management issues. The primary concern with excessive thatch is that moisture is held in this layer. This leads to greens holding too much water close to the surface, causing softer than desired surfaces, with the resultant foot printing and pitch marking resulting in bumpy, slow greens. 

Turfgrass agronomic guidelines recommend that the top 20mm of a green profile should target a total percentage of no more than 4% organic matter. Below is a table of three older greens on course and their organic matter test results.

The Next Step

With the current green conditions, the lack of sustainable control options for Couch encroachment, Poa annua control and the amount of organic matter present, these cumulative issues have led to the decision to undertake a Greens Resurfacing Program.  It is opportune time for the Club to undertake this process with irrigation requiring replacement and bunker revetting to be addressed. The resurfacing of greens will occur in conjunction with the role out of the Course Enhancement Plan.

As a part of the 2019 Practice Range facilities redevelopment, a new Practice Green was constructed.  With the implementation of a future Greens Resurfacing Program in mind, it was decided to utilise this new green as a trial site to assess several of the newer varieties of Bentgrass currently on the market and being grown on golf courses around Australia.  With the publicity surrounding the greens conditions some of the new course developments are receiving it is prudent that these varieties were assessed against the climatic and playing conditions present here at Glenelg, as well as their ability to be maintained at a level which is sustainable long term.

Bent Grass Selection & Trial Setup

The trial green was sown with seven different varieties and blends of Bentgrass, sown in plots measuring 5 metres by 7 metres.  Sown in May 2019, which is later in the season than desired, sees the cooler weather having an influence on germination time. However, with no pressure to have the green in play by a certain date, this issue was tolerated. The following Bentgrass varieties and blends were sown.

Argonomic Testing

One of the most important agronomic aspects to greens performance is how the variety or blend accumulates organic matter or develops thatch in the top 40mm of the soil profile.  Thatch is the term used to describe the layer of live, dead, or decomposing organic matter generated from the turf plant just under the turf surface. The accumulation of thatch, and given how quickly it builds, has a huge baring on the longer-term maintenance of the putting surface.  A variety that accumulates quickly will require more intense management practices, such as more frequent sand dustings, de-thatching (grooming) and hollow tine coring to manage or dilute the thatch layer. If thatch is allowed to build to excessive levels, above 4% of the total soil sample in the top 20 – 40mm, the surface is prone to several detrimental management issues, such as shallow rooted turf, excessive moisture retention, soft surfaces, and disease prone turf. The goal when selecting a variety is to select one that can be sustainably managed within Club resources, and one that the thatch biodegradation process is not too far behind the production, so it can be managed at a sustainable level.

Below are the results of Loss on Ignition Tests for each of the trial plots. This test measures the percentage of organic matter, in this case the top 40mm of soil profile. The test process includes a soil sample being weighed and then placed in a furnace where the organic matter is “burned” out.  Once cooled, the remaining soil is weighed where the percentage of lost organic matter is calculated.  The target for well-maintained turf surfaces is a percentage less than 4%.

Loss on Ignition Test Results

Brief

The seven samples submitted from the trial green for loss on ignition test, have been completed and the results are presented in the following table;

Comments

The results suggest:

• Mackenzie and Crystal Blue Links had the least amount of organic matter within the top 40mm of profile.
• The two varieties of Dominant returned similar results.
• Pure Distinction had comparable results to the A1 & A4 blend.
• The 777 had the highest amount of organic matter within the top 40mm of profile.

Thatch Depths of Selected Varieties

New Dominant Extreme Blend Thatch Depth = 20mm  |  Mackenzie Thatch Depth = 18mm

Conclusions

The initiative in running Bentgrass variety trails on the Range Practice Green has been extremely valuable with many significant findings revealed over the course of two years since sown. There are two distinct variety groups displayed, Bents with an aggressive growth habit producing ultra-dense, fine surfaces and Bents that are less aggressive, a little slower to establish however producing equally manageable surfaces under current practices.

When carrying out visual inspections, the plots that stand out due to their density, colour and texture (the qualities that are sought in a putting surface) are Pure Distinction, 777 and the A1/A4 blend.  All year round these plots stand out for the tightness of the sward, the fineness of leaf and colour, and they seem logical choices for the selection process for a Greens Replacement Program.  Pure Distinction has been a variety that has captured plenty of publicity due to its use in many high-profile greens conversion programs, most notably Peninsula Kingswood and Victoria Golf Clubs. The selection of this variety is due to its aggressiveness in growth habit and its ability to compete with Poa annua. The surfaces produced at these clubs are exceptional, however, with our own experiences throughout the trial it begs the question whether this variety, as well as 777 and the A1/A4 blends are sustainable for the long term. 

These three plots recorded the highest organic matter accumulation over the two years, in the range of 4.6% to 5.3% where the benchmark is <4%, combined with thatch depths from 27mm to 30mm, which longer term will create management issues. With the amount of thatch already present, there has been an increase in disease pressure on these three plots, as well as softer surfaces with foot printing present after heavy golfer traffic.

To counter these management issues, if any of these more aggressive Bents were adopted, there would be greater input in terms of management than currently implemented. Practices such as sand dusting, growth regulator applications and even extra corings would have to be considered to maintain these varieties at a standard that is required. This need for more maintenance input goes against the aim of selecting a sustainable variety.

The counter argument to the excessive organic matter build up is altering of management practices to mitigate the issue. A reduction in yearly Nitrogen inputs to these plots would have been a potential exercise that may have seen less accumulated organic matter build up without a reduction in quality. With the amount of traffic Glenelg experiences, a reduction in Nitrogen may expose the greens surfaces to a lack of recovery potential from golfer wear, pitch marks and maintenance traffic.

From the other trial plots (the two Dominant Blends, Crystal Blue Links and Mackenzie), the two that stand out are Mackenzie and the New Dominant Blend, made up of the varieties Flagstick, 007 and SR1150.  Both Crystal Blue Links and the old Dominant blend have produced satisfactory surfaces, however, they are open in their growth habit, giving Poa annua a chance to establish, and are courser in the leaf which does not provide the density and texture required. 

The new Dominant Extreme Blend, made up of three of the newer varieties of Bent on the market (007, Flagstick and SR 1150) are all bred for their leaf texture, density, and tolerance to a variety of environmental conditions.  With the agronomic testing carried out on the trial plot, this variety was mid-range in comparison with the others, with a 3.7% organic matter accumulation and 20mm of thatch build up.  Over the course of the trial there was little to no disease incidence.

The results from the Mackenzie trial plot were similar, with a 2.8% organic matter accumulation and a thatch depth of 18mm.  The Mackenzie plot was a little slower to establish, however, once full coverage was achieved, it has presented a surface with great colour, density, and texture with little to no disease incidence.

Recommendations & Rational

It is recommended that a blend consisting of 50% of the New Dominant Extreme Blend (Flagstick, 007 & SR1150) and 50% Mackenzie be adopted as the Bentgrass blend to be utilised in the greens resurfacing program at Glenelg Golf Club.

The traits exhibited by both these varieties throughout the trial period indicate that under the current management practices that they both demonstrate qualities that will be sustainable in the long term.  Both plots were in the low to mid-range with accumulated organic matter, had little to no disease incidence and coped with a variety of environmental conditions. 

The Mackenzie plot demonstrated that it was slower to establish as well as recover from renovations, which is its only negative point, however once recovered produces a very manageable surface that does not require excessive cultural practices to produce a fine, dense surface. 

In discussions with Superintendents who have management experience with Mackenzie, Gary Dempsey (former NSW Golf Club Superintendent) and Barry Procter (Woodlands Golf Course Superintendent), the take home message from both was that once established it is an extremely low input variety, producing a quality surface, however when looking for recovery needs to be pushed with extra fertility.

To counter the slowness of its recovery, blending with the Dominant Extreme blend, made up of more aggressive varieties of 007, Flagstick and SR1150 will assist with the wear tolerance and recovery rate from renovations, pitch marks and golfer traffic. 

Mid-way through the trial on the Range Practice Green it was evident, given the traits these two varieties were exhibiting, that it was a blend worth trialling. With the need to establish a Greens Nursery governed by time frames of a pending greens replacement program, it was decided to trial this blend, of Mackenzie and New Dominant Extreme, on a larger scale and sow it in the new Greens Nursery.

The nursery was sown in January 2020 and since then its performance has delivered results that has given confidence in its longer-term management.  There was some early disease pressure through its first summer, once treated though, has exhibited low disease pressure since. Organic matter percentages have not been tested however the thatch layer depth is low, sitting at 10mm.

Greens Nursery – 50% Dominant Extreme (New) Blend with 50% Mackenzie.
Thatch Depth – 10mm
Age of turf – 18 months
Age comparison between Nursery vs Range Green – 15 months vs 23months.

Currently maintained at a height of cut at 4mm to condition for turf harvesting. The first harvest, after sowing in January 2020, was harvested 7 months later which is an exceptional time frame from sowing to harvest.

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