Ground condition research

Here's a bit of an insight into the research that goes on behind the scenes to ensure natural turf grounds are in their best possible condition. Phil is a well respected industry figure and is basically the turf "guru" at least here in Victoria.


Phil Ford: part 1/4 A discussion of the condition of natural turf football fields and ground-related injury.

Article by Phillip Ford published on 16/09/2013

Phillip Ford
PhD candidate, University of Ballarat
September, 2013

Part one of four

For several years, the University of Ballarat has been investigating the links between ground conditions and injury in football. I live in Ballarat, and when I finished a long career as a teacher of turf management in 2008, I was fortunate enough to be taken on at UB as a PhD student to study the effects of agronomic (soil and plant) factors on ground hardness and traction, and the implications for ground-related injury. 

Apart from the more obvious problems (e.g. glass, rocks, holes, unsafe fences etc.), the two main factors linked to non-contact, ground-related injury in football are hardness and rotational traction. Excessive hardness is mainly linked to bruising, fracture and concussion, and excessive rotational traction has been linked to ankle and knee injury, especially anterior cruciate ligament (ACL) injury. 

To cut a long story short, my research demonstrated that the safest football ground, from both a hardness and a traction point of view, was a surface with full grass coverage across the whole ground. I should rename my thesis: “Football ground safety - the bleeding obvious”.

But it‘s not as obvious as it seems. Have a look at community-level football grounds at this end of the season. A lot of them are completely denuded of grass in the high-wear zones. This is accepted as normal and inevitable, but my research showed these denuded areas are where player safety is most compromised. Ground authorities need to do more to prevent this denudation by selecting the best grass species, managing traffic, and allocating sufficient money and resources to sustain this full grasscover. This is particularly problematic when water restrictions are in force. 

			&nbsp;&nbsp;<img height="200" src="" width="300" alt="Phil%20ford1.jpg">
	<p style="text-align:justify;">When I started my research, Australia was in the grip of the 1997-2009 “Millennium Drought”. Water restrictions on community-level grounds had led to the loss of turfcover on perennial ryegrass grounds, leaving them largely bare (see Figures 1 and 2) and unacceptably hard. Testing of council grounds in Melbourne by Michael Robinson, from Sportsturf Consultants, found that more than 25% of these grounds had Clegg Hammer hardness values greater than 200 gravities at the start of the 2007 and 2008 seasons, with values on some grounds reaching nearly 400g. Many councils (and their insurers) adopted a threshold of 120g for safe play, and as a consequence many community-level grounds were closed.</p>

Figure 1: Community-level, unirrigated Australian football field in Ballarat, December, 2009. Perennial ryegrass coverage has been devastated by drought, but a natural invasion of couchgrass in the goalsquare area is surviving well, as shown below in Figure 2.

The 120g Clegg threshold was largely based on research at Melbourne University by Dr. Ian Chivers and Dr. David Aldous, who assessed players‘ perceptions of hardness in elite-level football. The applicability of this research to ground-related injury in community-level football is questionable. In Queensland, research by Keith McAuliffe and Matt Roche concluded that Clegg values for community-level football grounds above 150g were “cause for concern”, and that the absolute upper limit for play should be set at 200g (McAuliffe & Roche, 2009). The American standard (ASTM F1702-96) doesn‘t set any Clegg threshold at all for natural turf. The question of a sensible upper threshold for football is critical, but as yet the medical evidence has not provided sufficient guidance on what it should be.

A recent meta-analysis of football injury studies by Petrass and Twomey (2012) concluded that there was an apparent risk of increased injury on harder/drier grounds, but that good quality evidence was lacking. Such evidence is susceptible to ‘confounding‘ factors. For example, harder, drier grounds allow faster running, which on its own could contribute to more injuries. Several of these studies found an ‘early season bias‘ of higher injury rates early in the season, which could be attributed to harder/drier grounds - but they could also be attributed to lack of fitness, or ‘attrition‘, where injury-prone p0layers suffer their injury and are removed from the player population for a long period. Remember, too, that nearly all of these studies are undertaken in elite or semi-elite football, not community-level or junior football. 

The most rigorous and direct injury study in community-level football was conducted by Twomey and colleagues (2012), involving 40 teams in Ballarat and in Western Australia during 2007 and 2008 (Twomey et al., 2012). They measured Clegg hardness over two seasons at nine locations on 20 grounds, and also recorded the nature, cause and location of injuries. Hardness levels through the study varied between 25 – 301g. A total of 402 injuries were recorded and for 352 of those the exact ground location of the incident was known, to allow matching with Clegg values. Only thirteen of those 352 injuries occurred on ground locations where hardness exceeded 120 g. Eight of those thirteen were player-contact injuries, so there were only five ground-related injuries on areas where Clegg values exceeded 120 g. And none of those five ground-related injuries was a concussion or a fracture. In fact, the severity of injuries on hard grounds was actually lower than on soft grounds. 

To conclude this section, there is no convincing evidence that dry, firm, hard surfaces contribute to higher ground-related, non-contact injuries in football. And there is no objective evidence on what the Clegg upper threshold should be for football grounds. This requires further research, but I agree with McAuliffe and Roche that a more realistic cause for concern for community-level football is around 150-160g.

Oh yeah, not completely unrelated but does anyone recognise the gentleman on the far right?



Oh yeah, not completely unrelated but does anyone recognise the gentleman on the far right? fxy.png[/IMG]

Looks a bit like Stacky.

Hint- leading goal kicker 62 & 63

charlie payne whom i used to buy my car tyres from in sydney rd fawkner in the mid 70's.

charlie payne whom i used to buy my car tyres from in sydney rd fawkner in the mid 70's.

What's his number? What's his name?
Number 7, Charlie Payne
Played back pocket ruck from late 64 onwards
Phil Ford: part 2/4 A discussion of the condition of natural turf football fields and ground-related injury.

Article by Editor published on 23/09/2013

My agronomic research initially looked at hardness on sand vs soil profiles.

(To read part 1 from last week, click here).

Soils become excessively hard when they dry out, but sands don‘t - in fact they become softer as they dry out. My tests showed that if the fines content (clay, silt and very fine sand component) of a rootzone was less than around 17%, it would not become excessively hard when droughted, even if bare. In addition, the fines content of a rootzone needs to be less than around 11% to provide a sufficient infiltration rate for drainage (e.g. greater than 30mm/hr). So the conclusion was that re-constructing fields in sand could solve any hardness problems, even in drought. However, as many turf managers are aware, sands can become very shifty in drought if they lose their grass coverage. My tests showed that rootzones with a fines content less than around 15% have undesirably low shear strength. So if grass coverage is lost in high-wear zones such as goalsquares, the sand rootzone can be easily kicked out, causing depressions that are dangerous and extremely difficult to manage. Consequently, sand-based grounds should have less traffic put on them than soil-based grounds. This is a hard concept for parks managers and football clubs to understand – they have just spent $500,000 on a new construction, and you‘re telling them to schedule LESS play on it, not more! The bottom line is, sand-based football grounds can drain well and will not become excessively hard when droughted – but you need to control the usage, and don‘t allow any high-wear zones to become denuded of grass. 

My agronomic research then looked at the influence of grass coverage on hardness. It may seem obvious, but in fact there is very little research on this, especially in drought conditions. I set up two zones (one grassed, one bare) on the edge of a sports oval at Ballarat University. The soil was a fine clay, which I compacted several times prior to the trial, and the area was unirrigated. I measured Clegg hardness and soil moisture over an extended drought period, as shown on Figure 3: 

			<p><img height="450" src="" width="611" alt="phil%20ford%20graph.JPG"></p>
			<p>Figure 3: Relationship between Clegg hardness and soil moisture in plots with-grass and without-grass. The soil moisture probe was unable to penetrate when soil moisture fell below 3%.&nbsp;</p>


The graph shows that, obviously, soil moisture content has the greatest influence on hardness in this soil type. However, it also shows the benefit of having grass coverage. The presence of grass (the green dots) resulted in Clegg hardness in this soil only reaching around 150-160g when it was very droughted. Without grass, in contrast, hardness reached 250g when it was dry. If the Clegg safety threshold was set at 160g, then the presence of grass cover would allow this field to remain open. A lack of grass coverage would cause it to be closed.

I tested the effect of several other agronomic variables on hardness, but I concluded that the most practical way to eliminate excessive hardness on soil-based fields in drought was to maintain full grass coverage, over the whole ground and through the whole season. Sounds simple, but in a drought it isn‘t simple at all. It clearly couldn‘t be done with perennial ryegrass. 

Look back at the couchgrass area in the goalsquare in Figures 1 and 2. That‘s a natural invasion of a local couchgrass, which is extremely drought and wear tolerant, and capable of sustaining a full sward of grass even in severe drought. Councils that successfully converted grounds from perennial ryegrass to couchgrass through the Millennium Drought ended up with excellent grounds, despite the water restrictions. However, many councils didn‘t adopt couchgrass, either because the conversions were too disruptive, or because of a warning from medical research that couchgrass had a higher risk of ACL injury than perennial ryegrass, due to its excessively high rotational traction. That is the topic of part two of this report.

Acknowledgements: Phillip Ford would like to thank PGG Wrightson Turf (Australia), Strathayr and Rocla Quarries for their material assistance in this project.

References: available on request

Gimme the ground conditions at cold blow lane

Phil Ford: part 3/4 A discussion of the condition of natural turf football fields and ground-related injury.

Article by Phillip Ford published on 30/09/2013

The previous part of this article presented evidence that maintaining full grass cover on a field could prevent excessive hardness (i.e. greater than 160g), even on soil-based fields during drought.

If the hardness threshold for community-level football fields was set at 160g, then most fields could remain open for play if it was possible to sustain a full cover of grass.

Only a warm season species such as couchgrass could do that. However, Australian research over many years by Dr. John Orchard and colleagues had linked couchgrass to a higher risk of anterior cruciate ligament (ACL) injury compared to perennial ryegrass. This was attributed to couchgrass having a greater tendency to “trap players‘ boots preventing the free rotation of the foot and placing more stress on the knee ligaments” (Orchard, Chivers, Aldous, Bennell & Seward, 2005). They were clear that “Bermudagrass…has been shown to lead to higher ACL injury risk levels than ryegrass” (Orchard et al., 2008).

ACL injury has serious costs and consequences for individual footballers, their clubs and the wider society. It is a serious problem in all codes of football, and in many other sports as well. It is undoubtedly the most intensively researched sports injury in the world, yet the factors involved and best strategies to reduce injury are still unclear, and hotly debated. In football, the most common situation leading to ACL injury is the evasive ‘cut‘ manoeuvre, where a player decelerates onto a planted foot and pivots to change direction. Because of this, there has been a strong theory that excessively high rotational traction between the boot and surface was a causal factor in the injury. Considerable research in the US and Europe has focussed on boots and studs. A landmark study in American football by Torg and colleagues showed that mandating a switch from high-traction boots with 19mm studs (rotational traction 74 Nm)  to low-traction boots with 9.5mm studs (rotational traction 38 Nm) led to a 78% reduction in knee injuries requiring surgery over the following two or three years (Torg & Quedenfeld, 1973; Torg et al., 1974). It seemed clear that stud length and its effect on rotational traction was a major factor in ACL injury.

The Australian research of Orchard and colleagues ignored boot factors and focussed on surface factors, especially the grass species. Orchard argued against players being forced to wear low-traction boots as they would not want to risk falling, whereas making changes to the playing surface would lead to a universal reduction in shoe-surface traction affecting all players (Orchard, 2005). Although his data did not include any direct measurement of rotational traction on football grounds, or a direct traction comparison between couchgrass and perennial ryegrass, he recommended that “if it is possible to use ryegrass in the profile of a football field then this should be done” (Orchard, 2005). He also recommended oversowing couchgrass with perennial ryegrass to create lower shoe-surface traction and reduce ACL injury risk (Orchard & Powell, 2003). These recommendations led to the elite-level AFL fields being either converted to pure perennial ryegrass, or having their couchgrass base oversown with ryegrass. Unfortunately, in the decade or so since this has occurred, ACL injury rates in the AFL have not fallen; in fact the last three years have been at near record levels.  

Although Orchard‘s recommendations were aimed at elite-level grounds, the trickle-down effect contributed to a reluctance for managers of community-level grounds in southern Australia to convert from perennial ryegrass to couchgrass. So when the drought hit in 1997 and with the subsequent water restrictions, perennial ryegrass grounds were devastated and many were closed due to lack of grasscover and excessive hardness. Couchgrass grounds, however, sustained grass coverage and were in relatively good condition. Remember the photos in Part 1 of this article. So turf managers could see with their own eyes the benefits of couchgrass compared to perennial ryegrass, but the concern among ground authorities (and their insurers) that couchgrass would lead to higher rates of ACL injury reduced its adoption in many councils.  It was clear that a comparison of the rotational traction of couchgrass and perennial ryegrass was needed.

Various devices are used to test rotational traction, the most widely-accepted device being the Studded Boot Apparatus. It uses 46kg of weight imposed on a flat disc fitted with six football studs (see Figure 1), and this is rotated until the turf is disrupted and the studs tear free. This only occurs when the disc has rotated around 25 – 40 degrees, and the torque at which it occurs is called peak torque, which is measured in Newton-metres (Nm) using a torque wrench. A peak torque less than 20-30 Nm is considered too low for athletic performance in football, whereas values over 75 Nm are considered excessive for reasons of ACL injury risk. 

At the University of Ballarat, we were fortunate to obtain an automated version of the Studded Boot Apparatus (see Figure 2), developed by Les Zeller in collaboration with Dr. Don Loch and others at the Queensland DPI Turf Research team. In addition to peak torque, this device actually measures the increase in torque during the twisting process. The rate of increase in torque, termed rotational stiffness, is considered more relevant to ACL injury than peak torque. Medical research has shown that an ACL rupture in a football cutting manoeuvre occurs within a fraction of a second of the foot landing on the ground. Peak torque is only reached after 25-40o of rotation, which is very late in the test, and it is doubtful that any athlete‘s foot would even rotate that far in a manoeuvre. Rotational stiffness is measured right from the start of footstrike, so is considered to be much more relevant to ACL injury.

Two huge rebuilds HG Sports Turf are about to undertake the resurfacing of two of Australia‘s biggest stadiums.

Article by Amy Foyster published on 22/08/2014

HG Sports Turf are about to undertake the resurfacing of not one, but two of Australia‘s biggest stadiums.

Erik Kinlon, general manager for Melbourne based HG Sports Turf, is responsible for overseeing the resurfacing of the MCG straight after this year‘s AFL Grand Final. 

Meanwhile, Erik‘s NSW based counterpart, Nathan Humphreys, will be looking after the resurfacing of ANZ Stadium at the same time, in what is sure to be a busy period for the company.

Erik says that because of HG‘s unique portfolio of proprietary turf systems, the overall operation can be very diverse. The systems they offer are on show in some of the world‘s most iconic venues with a product range that includes natural turf, stabilised turf, hybrid turf and synthetic turf. 

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	<p style="text-align:justify;">HG has been the supplier of stabilised turf to the MCG since the late nineties, so have a long and distinguished relationship with 'The G'.&nbsp;</p>

“We were tasked with the last rebuild of the field before the Commonwealth Games in 2006 so we have a clear understanding of the project ahead,” says Erik. 

“The Motz stabilised turf system we use has been redeveloped in conjunction with The Motz Group and is now called Eclipse Stabilised Turf. It is jointly patented with HG Sports Turf and the Motz Group. 

“This is the stabilised turf that both ANZ and the MCG will have installed later this year. Obviously there are other reinforced turf systems out there but we feel that the Eclipse leads the way, because it stabilises the surface.”

Erik says that the whole process has a few specific steps. 

“We initially establish the turf at the turf farms by laying a field of the patented Eclipse carpet, then we infill it to a profile depth of 40mm and grow the natural grass in this profile. The turf is matured by our highly experience sports turf managers at the turf farms until stadium ready. It is then harvested and brought to the stadiums, where it is laid as a ready to play system.

“With the MCG project, we will be stripping the top off and removing some material in order to bring the field back to the original design levels from when it was last reconstructed in 2006 for the Commonwealth Games. 

“Following the initial surveys to identify the cut requirements, the first leg of the process is to take the top off the ground and that will be done with mechanical excavators and also Koro Field Topmakers, with the material being stockpiled for removal. 

			&nbsp;&nbsp;<img height="200" src="" width="300" alt="MCG_Game%20Day.jpeg">
	<p style="text-align:justify;"><em>“Then the next step will be to re-grade the profile back to design levels in preparation for the Eclipse Stabilised Turf.</em></p>

“Once the final grading and surface preparation is complete the turf laying process will commence. A very co-ordinated approach will be adopted in order to relay the 18,000m2 plus, in line with the project program.

“The Eclipse Stabilised Turf is a ready to play system and this will be seen in full effect at ANZ stadium when Australia plays South Africa in a cricket T20 game just five days after final turf install.”

Just like the longstanding relationship that HG has with the MCG, they have also been involved at ANZ for many years going back to the Sydney 2000 Olympic Games. 

At both stadiums they supply and install a significant quantity of turf annually for their turf replacements throughout the year. 

Both of these resurfacing projects are scheduled ahead of major sporting events with the ICC World Cup at the MCG and the Asian Cup at ANZ, something that Erik says is probably the biggest challenge with a project of that scale. 

“The overall planning process and project management is vital to the success of the operation,” admits Erik. 

“There are just so many different variables that can have an influence in terms of delivery of the whole project and you have to pre-empt these and make contingency plans to ensure expectations are met.”

While it can be challenging, Erik says that there are a lot of rewarding things about working on such high profile venues. 

“Sometimes you just pinch yourself, working somewhere like the MCG or ANZ, the most preeminent sports stadiums in Australasia. 

“The collaborative approach from everybody involved from start to finish is also extremely rewarding.  

“But ultimately the greatest satisfaction is watching an event that is televised globally, knowing that you had a part to play in it. And yes, there might have been some ups and downs along the way, but nobody ever sees that on game day.”

Whatever they do at Homebush is not working.