Time to do things differently?

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Time to do things differently?: With the world’s oldest golf courses being almost exclusively links courses it is no coincidence that very sandy materials have traditionally been used for the construction and refurbishment of coastal and inland golf courses across the world. 

Sand provides a firm, level and well drained playing surface. Because it is inert it does not hold onto nutrients or water and this allows greenkeepers to manufacture the environment required through the addition of artificial fertiliser and the introduction of water through irrigation.

Time to do things differently?

Time to do things differently?

Notwithstanding the unprecedented, and unexpected, positive impact of the current pandemic on the global environment, our climate continues to change. For some time, scientists and consultants working in the industry have been looking at how golf course construction and refurbishment could be done differently in the future, using materials that are better suited to work with the vagaries of the climate, have a less detrimental impact on our environment, and reduce annual costs.

The use of soil and soil-based products to construct, refurbish and maintain tees, bunkers and green surrounds is proving increasingly popular with greenkeepers and golf course consultants who have been encouraged by STRI research, feedback from scientists, and industry case studies and testimonials.

A good soil is a mixture of mineral particles – sand, silt and clay – water, nutrients – predominantly nitrogen, phosphorus, potassium and magnesium – organic matter, air and living organisms. ‘Virgin’ or ‘as dug’ natural topsoil as a construction material for shaping course features, tees, bunkers etc. is neither sustainable nor reliable.

Not only are the world’s soil resources being depleted at an alarming rate but virgin soil is also a ‘take it or leave it’ material that may lack the right balance of the constituents listed above, affecting its performance.

British Sugar Topsoil products are sustainable, being derived from the prime arable soils that adhere to the sugar beet brought in to British Sugar factories. The soil is washed from the beet and collected in settlement ponds before being conditioned and blended.

To comply with the British Standard for Topsoil BS3882:2015, each batch is sampled and sent to a UKAS and MCERTS accredited laboratory for a range of tests.

Topsoil products have also undergone comprehensive replicated trials at the STRI.

Good grass establishment and growth, particularly in periods of drought, and the recovery of the sward following periods of heavy rain, make soil-based materials for course construction and refurbishment a very attractive proposition.

The clay component in soil holds on to nutrients (N, P, K, Mg) and the microbes present in the organic matter make for a healthy soil, resulting in good grass establishment and growth and minimising the requirement for additional and expensive inorganic fertiliser. Soil also has a considerably slower percolation rate than sand and this increased waterholding capacity means that areas are less reliant on irrigation. And in terms of course design, soil’s plasticity allows the creation of more interesting and challenging contours and features.

With all that said, maintenance remains key to the successful use of soil products and, where used, the ground must still be aerated on a regular basis to prevent compaction and puddling.

Perhaps, in this period of unexpected lockdown, there is time to look at doing things differently, working with the natural world’s own resources in a sustainable, cost-efficient and environmentally beneficial way.

At Bury St Edmunds Golf Club Consultant Peter Jones, of Peter Jones Associates, selected British Sugar Topsoil’s Landscape20 topsoil for the re-shaping and re-contouring of the entire green complex. 120 tonnes were spread at a depth of 15-20cm over the course’s natural sandy loam soil, which had been de-compacted and levelled using a purpose-built rake.

Finally, a dwarf perennial rye grass turf was laid over the Landscape20. Throughout the entire operation the putting surface of each green was left intact.

Peter chose Landscape20 because of the success he had had with it on similar projects: “The properties of Landscape20 allow you to create the shapes needed around bunkers and greens, and the naturally occurring nutrients within it result in great turf growth.”

At Peterborough Milton Golf Course, 13 bunkers were re-shaped and five tees levelled with 174 tonnes of British Sugar TOPSOIL’s Sports&Turf topdressing prior to re-turfing. “Sports&Turf is by far the best product I have used in my years as a greenkeeper and I am delighted with how easy it is to use. The drainage and percolation rate it gives is second to none,” said Manager Steve Smail.

Dealing with global extremes

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Dealing with global extremes: STRI’s head of sports surface technology, Dr Stephen Baker, considers the problems of turf management in some of the more extreme climates that he has visited in his 38-year career.

Working conditions

Grass selection and maintenance is very dependent on climate, and in many parts of the world there is not the relatively benign climate for turf grass growth that we experience in the United Kingdom.

Whilst there can be significant issues with snow and frost in the winter, average monthly temperatures in the UK typically range from around 0°C to 20°C and this is a relatively comfortable range for grass growth for most of the year.

Dealing with global extremes

Dealing with global extremes

Contrast this with some of the sixty countries that I have worked in. Parts of Russia or Scandinavia where the average minimum January temperature of -15°C to -20°C (and lows of -40°C) and average maximum monthly temperatures of 38°C to 43°C in India, Morocco and Saudi Arabia, with peak temperatures sometimes exceeding 50°C, made for some interesting working conditions.

Similarly, in the UK we have a relatively reliable rainfall and without the very high intensities experienced in some tropical areas.

Annual average rainfall in the UK typically ranges from around 700-1250mm per year for the more heavily populated parts of the country where most sports facilities are found.

In contrast annual rainfall can be as low as 100mm in Saudi Arabia. At the other extreme, average monthly totals can reach over 300mm in Manaus in the Amazon Basin in Brazil or in Kuala Lumpur, Malaysia and massive 840mm in Mumbai, India. It should be noted that these are just average values and at times the temperature range and rainfall differences can be much greater. It is inevitable that extreme variations in temperature and rainfall will increase the challenge of producing high quality sports surfaces.

Low temperatures

The map, above, shows the range of climates around the world from the perspective of turf management.

Each of the climate areas has a major influence on selection of the appropriate grass species in relation to the ideal temperature range. However, there is also a wide range of other issues such as drought and salinity tolerance, the sports to be played and the potential standard of maintenance, including irrigation demand.

Fortunately, a very wide range of grass species are available, and they can be split into two very different groups depending on their basic biology: the cool-season grasses and warm-season species. Cool-season grasses would include species such as smooth-stalked meadow-grass (Poa pratensis) and perennial ryegrass (Lolium perenne), which are used on areas of more intensively used turf such as football or rugby pitches, and finer fescue (Festuca spp.) or bent species (Agrostis spp.) that may be suitable on areas such as golf courses.

For areas of extremely low temperatures it is inevitable that appropriate cool-season grasses will be used, but there are several aspects of management that may need to be considered:

• Minimum temperatures that are likely to be encountered
• The length of the growing season, in particular how much of the playing season coincides with periods of minimum growth
• Duration of snow cover and the need for snow removal. Snow cover is indeed often used as an insulating blanket to protect the turf during the coldest months of the year, but there can be significant challenges in clearing the snow and making the surface ready for the start of the new playing season
• The potential risks for disease, especially under snow cover or during periods of limited growth
• The opportunities for pitch renovation. In the more extreme climates for example of North America, Scandinavia and Russia the main playing season will coincide with spring, summer and early autumn when growing conditions are generally better. However, this may limit the amount of time available for renovation, as for example end-ofseason work would coincide with lower temperatures thus preventing effective grass establishment

As well as selection of suitable grass types there are several management options that may improve the standard of turf in very cold climates.

Undersoil heating and pitch covers are generally essential for the major stadiums in such climate areas and, as latitude and cloud cover have a major influence on light levels, most stadiums in these colder climates would also need supplementary lighting to extend the period of grass growth.

Maintaining a high standard of grass cover can also be a big issue in these colder climates. Annual meadow-grass (Poa annua) is very well adapted to the colder, wetter climates such as Iceland or the west coast of Norway.

Without the possibility of extensive end of season renovation there are only limited opportunities to establish preferred species, so annual meadowgrass tends to increase rapidly with time. To maintain a reasonable balance of grass species there is a need for regular over sowing throughout the summer months, with ideally a break in the middle of the playing season to allow a short renovation window.

High temperatures

High temperatures cannot be isolated from rainfall and there tends to be two main extremes where high temperature and rainfall interact: (1) high temperature but low rainfall in desert or semi-arid environments, (2) high temperature, high rainfall areas, although these can have a distinct wet season and a dry season which will have a major impact on turf management. For the monsoon season in Mumbai, India, the four months between June and September have a combined average of about 2250mm rainfall, while the four months from January to April have a combined rainfall of less than 5mm.

The main factor influencing grass quality in hot climates with either low annual rainfall or seasonal drought, will be water supply through irrigation and a good quality irrigation supply will be essential. For high standard stadiums water will generally be delivered using an appropriate pop-up irrigation system, but for more general, lower maintenance areas techniques such as subsurface irrigation may also have to be considered to improve water conservation.

Grass selection is normally based on warm-season species such as bermudagrass (Cynodon spp.), seashore paspalum (Paspalum vaginatum) or various Zoysia species, but there may be other considerations.

Dealing with global extremes

Dealing with global extremes

In the absence of cloud cover, nighttime temperatures in some desert climates can be very low giving a risk of dormancy of the warm-season grass. In some wetter tropical climates, particularly where there is significant photochemical air pollution in major urban areas, light levels might be insufficient to maintain healthy grass growth at certain times of the year, especially in stadium environments.

A further factor compounding issues of heat stress in many of the drier climates is the quality of the irrigation water and the potential build-up of salts in the soil. Assessment of water sources for irrigation becomes a major item in turf design in such areas and regular excess irrigation may be needed to flush accumulated salts out of the rootzone.

Very hot, wet areas also have some very specific challenges: these include high intensity rainfall (which I’ll discuss later) but also high rates of biologically activity and this can have particular challenges with disease, insect pests and weed invasion.

Management of the turf in the hottest parts of the world must consider all these issues. There are however some management techniques that can also restrict temperature stress, including:

• air circulation systems by which cooler area can be pushed from lower in the soil profile to cool the grass at the surface
• syringing with light applications of irrigation water to dissipate heat by evaporation
• shade covers mounted well above the grass surface to restrict the incoming solar radiation
• installing cooling pipes, reversing the principle of undersoil heating.

Transition zones

Some of the biggest challenges with grass selection occur in transition zones where there are extreme ranges of temperature. These include Mediterranean type climates in parts of Europe, South America, South Africa and Australia but also some of the continental extremes, where winter temperatures can be as low as -30°C, while summer temperatures may hit 35°C.

Under these circumstances a single grass type is very unlikely to be able to tolerate the annual temperature range: warm-season grasses will go brown and dormant in the winter and cool-season grasses are likely to be lost to heat stress and disease in the summer period.

Good management is obviously essential in such climates, but inevitably more than one grass species will be required, with the warm-season grass used in the summer and then being oversown with a cool-season grass to give the colour and performance required for the winter months.

Rainfall

It is impossible to provide a good quality turf surface without adequate irrigation and issues of turf management in hot, dry climates have already been discussed above. However, there are methods to improve the water retention properties of sports turf rootzones using various organic and inorganic amendments. The type and concentration of these amendments is critical – too little amendment and the surface may remain dry and hard. Excess amendment can lead to a soft playing surface, with shallow rooting that is easily damaged by play. Laboratory testing and a very good understanding of requirements for the growing medium is essential to help formulate the most suitable rootzone characteristics for a specific climate zone.

Very high rainfall is also an issue, as most sports surfaces rely on a relatively dry, stable surface for optimum playing conditions. Well-constructed rootzones, usually based on a high percentage of a suitably selected sand, are generally essential to give adequate drainage performance.

However even a well-constructed rootzone with a drainage rate of say 150mm/hr will not be able to cope with the most extreme rainfall events. In such circumstances it may be necessary to construct a turf facility with greater slopes to encourage surface runoff of water.

Dealing with global extremes

Dealing with global extremes

Technology can also help – many of the subsurface air circulation systems used for temperature control can be used to generate sufficient suction within the soil to help remove extreme rainfall from the surface.

Wind

Excess wind may sound more like a complaint of the digestive system than a problem faced by most sports turf managers, however there can be situations where high winds (or indeed a lack of air movement) can be a factor in sports turf management.

Aside from destructive events such as hurricanes, the most likely problems of high wind would be on exposed sites where irrigation can be affected.

If there are strong prevailing or drying winds, evaporation rates are likely to be higher and therefore water consumption greater. However, it is the effects on water distribution that may be the greatest challenge, as the effect on the uniformity of water application can be significant.

This may necessitate changes in the basic design of the irrigation system with for example changes in the specification for the pop-up heads or sprinklers at closer spacings than on a less exposed site. It will also increase the need for careful monitoring to ensure that there are no dry areas that are being missed and for selective hand watering to supplement moisture levels on any drier areas.

Lack of significant air movement should also not be under-estimated. In modern stadium environments the surrounding stands may restrict air movement to the extent that drying of the surface is compromised and the risk of disease and surface algae may increase.

Where there is temperature stress this can be even more important, for example with cool-season grasses growing at times of elevated summer temperatures. Under these circumstances the use of fans around the pitch to help air movement can be a very important factor in reducing turf stress and sustaining a high-quality playing surface.

Modern sports turf management

In the last 40 years the range of available technology has expanded to an unbelievable extent. The understanding of turf construction and management principles has improved, by both technological innovation and research investment. More marginal climates that gave high levels of stress affecting grass development can now have much better-quality turf surfaces, provided that development projects are well designed and constructed and that there are sufficient levels of resources to deal with these climate extremes.

New lawns shown NO MERCY

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New lawns shown NO MERCY: Scott MacCallum gets to grips with EGO’s battery powered mower.

As a journalist, I am far more adept at writing about things than actually doing them. A theatre critic cannot be expected to deliver an emotion drenched soliloquy, nor could you rely on a sports writer to produce a smooth Cruyff turn.

New lawns shown NO MERCY

New lawns shown NO MERCY

And so we come to me and lawn mowers.

I must admit I’m what Capability Brown would be to feature writing, or Shakespeare to designing a Chelsea Garden. Not the best.

However, we have three lawns on our recently-acquired home and, once there is a little heat in the air, that grass does grow.

So, I was delighted when EGO asked me to road test their latest battery powered mower – the 42cm cordless self propelled mower – which joined the EGO stable earlier this year.

The excitement when the delivery van dropped off the large box was palpable, and, I’ll admit it now, tinged with a little apprehension. How easy would it be to transform the contents of the box into a working lawnmower?

The answer? Simple! Even a man of my limited practical means had it up and running in 15 minutes – a more proficient human being would have achieved the same feat in five, but I still saw it as both a feather in my cap and that of the EGO.

The mower is beautifully powerful and given that not only was it my first outing with the mower, it was my first attempt at circumnavigating our new lawns. Now I can tell you that while the intricate scallops and dainty satellite flower beds looked absolutely superb on the Estate Agent particulars, when it comes to lawns, I’d far rather have straight up and down squares and rectangles. So much easier.

However, we are where we are and while my first two cuts saw a degree of trial and error on the part of the driver, by the third cut I considered myself to be pretty capable. Those early attempts were characterised by my efforts to control the throttle. The self-propelled element is absolutely wonderful, but a brain has to become acquainted with the fact that the mower won’t stop until you released the handles on the top of the steering console.

I haven’t told my wife yet, but the odd area of the border where the shrubs and flowers are a little more dishevelled and scruffy – I’d be inclined to use the word “gouged”, are not the legacy of the previous owners, or next door’s dog, but my failure to adapt quickly enough to the self-propelled nature of the EGO.

It can run away with you a little and if one of the wheels slips off the side of the lawn it can leave an impact, in most parts negative, on the vegetation.

But once I had mastered both the mower and the lawn I truly was poetry in motion. The speed is controlled by a very simple dial in the middle of the console and this can be ramped up on a straight run – our lawns do possess a few – and reduced when it comes to the more twisty bits.

At 42 cm wide it is a nice balance of wide enough to reduce your mowing mileage and narrow enough to negotiate tighter spaces.

The grass box, part hard plastic, part fabric, is easily accessible and roomy – is that a word you can use for a grass box? A full box roughly fills a standard black bin bag and it is extremely simple to remove and reattach.

All that power I mentioned takes a little bit or servicing and I was pleased that I had been sent an additional 56 volt 5ah battery to complement the 2.5ah battery which came with the mower.

Our grass take around 40 minutes to cut and that would account for the entire life of the smaller battery or around three fifths of the larger – the battery indicator is split into well illuminated fifths so you can see how much you have left – so having a spare battery, which you can have charged and ready to step in, is extremely useful.

I have now used the mower for around half a dozen cuts and it has not caused me a single problem. I’d go so far as to say that it has made cutting the grass a real pleasure and I’ve not gone looking for an excuse for not mowing the lawn – a weather forecast showing even a slight chance of rain would previously have been enough for me to shelve the idea.

I’m certainly sold on battery power. My previous mower was a fine electric powered model and unwrapping from clothes poles and deciding which was the better option – a left or right turn to avoid running over the cable were all part of the experience.

So, I might not be the finest lawn mower man in the country but, at least, I’ve been able to come to some sort of definitive conclusion as a lawn mower tester!

Eon Bio – a time capsule with a difference

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Eon Bio – a time capsule with a difference: David Snowden discusses the benefits of improving your growing medium and why using a soil conditioner is such a valuable tool…

The main benefits of soil conditioners are to improve the soil structure and therefore increase nutrient uptake and root mass. When applying to new greens at renovation time and when used on sports pitches to create a root zone with life in, soil conditioners increase the efficiency of nutrition.

Eon Bio – a time capsule with a difference

Eon Bio – a time capsule with a difference

We want to bring life to the soil and this is what Eon Bio enables our Greenkeepers and Groundsmen to do. When the grass plant germinates, it needs a bio-available food source and we require rapid establishment of the new plant to secure a healthy sward.

We have seen great success working with numerous Premier and Championship Football Clubs, when using Eon Bio, which has the benefit of a prill form, particularly easy to use.

Eon Bio is 100% organic and contains high concentrations of soluble, slow release Humic acid. This ‘time capsule’ releases and encapsulates mycorrhiza fungi and multiple forms of beneficial bacteria, which solubilise phosphates. We need to feed our soils to create the best growing environment.

With Eon Bio, the guess work is taken out, as the bacteria is specifically cultured and proven to benefit the soils and our grass plant, all wrapped up in a Humic acid food source for bacteria.

Surf ‘n Turf

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Surf ‘n Turf: A horse’s impact on a surface, whether a racecourse or eventing track, has been much debated in sporting circles. On a professional sports stage the horse, averaging around 500kg, makes a significant collision with any surface. STRI agronomy manager, Steve Gingell, puts on his farrier’s hat to study hoof interaction with grass.

There have been several publications on the action and stages of horse’s hoof interaction with a surface. However, most are related to artificial sand surfaces and less so to grass surfaces.

Surf 'n Turf

Surf ‘n Turf

The key works are from the FEI Equestrian Surfaces Guide published through the Swedish Equestrian Foundation and Natural Turf for Sport and Amenity by Adams and Gibbs. ‘Science and Practice’ reviews the surface interactions at several racecourses in terms of firmness, penetration and resilience over time.

This is also a useful guide to how a hoof interacts with the surface.

There are a few testing devices simulating hoof interaction with different types of turf surface. The main equipment used on artificial surfaces is the Orano Biomechanical Surface Tester. This aims to mimic the phases of a hoof’s interaction with a surface.

Testing is also undertaken on turf using devices such as the TurfTrax Going Stick and the STRI Toro Precision Sense Testing, which gives data and maps indicating the surface performance. So how does a sports turf manager adapt their surfaces to ensure a safe and fast or competitive surface for a range of equestrian sports?

SURFACE HOOF INTERACTION

The majority of professionals accept that there are four stages of a hoof interaction with the surface.

Touch down

Where the hoof initially impacts the surface; this is a braking force. The hoof will receive a shock/feedback from the surface depending on whether it is hard or soft. Very hard surfaces will give injuries to the hoof and leg bones. Very soft surfaces give very little feedback as most of the energy of the initial shock is absorbed through the surface.

Loading

Where the full weight and impact of the horse focuses through the hoof. Typically, forces are vertical and therefore the surface firmness is much more important. Hard surfaces will injure tendons, ligaments and bones.

Soft ones give little feedback to the hoof and therefore energy of the motion is lost.

Surf 'n Turf

Surf ‘n Turf

Roll over

Where the toe of the hoof starts to push into the surface. A firm, surface can give little grip as the hoof slides on the surface. A very soft surface could dig in and lead to significant divot removal and lack of pace.

Push off

The most important aspect of this stage is a strong turf as this is where the horse is gaining propulsion. The toe is at the maximum penetration and the flat of the hoof is pushing backwards. Traction is vital and therefore an over soft or damaged surface could give little traction.

FIVE FACTORS AFFECTING HOOF INTERACTION AND SURFACE PERFORMANCE

Impact firmness

The surface needs to have impact firmness, ie absorb shock when the hoof hits the ground. This is most important in a profile upper layer hardness. As an example, a very soft surface will have low impact firmness and a tarmac or a bound surface have very high impact firmness. This is very important in avoiding horse injury.

Cushioning

A surface needs to dampen and reduce impact forces (cushioning) and is achieved in various layers within the surface. A well cushioned surface reduces stress, ie soft racecourse, whereas a firm surface is fast but could cause injury.

Grip

Grip is important because a very low grip surface means the hoof slides and therefore injury can occur, whereas a very high grip surface can often have high impact forces. A surface must be able to withstand push off. It is important that some slide occurs to reduce the forces on the hoof.

Surf 'n Turf

Surf ‘n Turf

Responsiveness

Responsiveness is a measure of how active or springy the surface is. A responsive surface gives energy back to the horse and this aspect is also related to the firmness and cushioning. A very compacted hard surface may rebound too quickly, whereas a very soft surface will give very little responsiveness.

Uniformity

A surface needs to be uniform so that the horse has confidence to reach its maximum performance. Variable surfaces, particularly in very short distances, can be significantly problematical.

HORSE RACING

In horse racing, the key aim is to provide a fast track that is both safe and fair. In flat racing typically, surfaces are maintained to a slightly firmer level with slightly shorter grass length than jump racing. The aim however must be to provide a reasonable level of cushioning and a medium to high level of impact firmness.

If a course becomes too firm, then the impact firmness becomes high and horses can suffer injury. Conversely, an over soft surface means speed and times are slower, therefore horses will tire more quickly. Grip is also important as horses will be using their maximum level of propulsion push off due to the high speeds of travel. There would be less grip issues as the hoof is not having to absorb any braking that would occur when using a jump.

In jump horse racing speeds are lower, and in between jumps over firm ground can create issues in a similar manner as flat racing. There is also a tendency to prefer a slightly softer going to ensure reasonable safety and moderate times. This is partially achieved through racing in winter months when soils are naturally wetter and therefore have less impact firmness, but also through a slightly longer height of cut at around 4-5 inches to give a little more cushioning.

When a horse jumps, grip in the initial stages is important, and then impact firmness and cushioning is vital on the landing phases.

Over a racecourse there will invariably be a degree of difference in uniformity as often different soils will occur, unless that track has been completely reconstructed. It is difficult sometimes to manage uniformity which is only achieved through varying aeration, irrigation cycles and fertility.

Surf 'n Turf

Surf ‘n Turf

CROSS-COUNTRY

Cross-country builds on the comments in horse racing. There will be sections of galloping between the sets of fences, coupled with explosive takeoffs, moderate impact landing forces and often turns a stride or two after.

It is important for horse safety that the track is of medium firmness to reduce the impact and has a good level of cushioning. This is usually achieved through a reasonable grass length, although grass height is much lower in eventing than would be in racecourses. So there needs to be appropriate irrigation strategies and grass health management through aeration and fertility to maximise the soil cushioning.

Grip is very important as a horse needs to feel confident to take on the various obstacles. Lack of grip means the horse may slide forward towards a jump or not have suitable footing on landing. As an event progresses the take-offs and landings will often become quite worn. Therefore, exceptional management with good levels of repair in these areas, running up to a meeting, is very important. Frequently woodchip or even gravels are put in and around a landing zone and these will tend to make surfaces very firm over time and should be avoided.

Aeration and an overseeding or returfing of poor areas immediately following an event is essential to maximise the turf condition.

POLO

Polo is interesting in that each horse will only be used for a very short period, but under a very intense level of activity. Due to polo being a ball sport the surface is also kept very short. The surface needs to have a moderate to elevated level of impact firmness, but not to a level that the horse becomes injured because of the shock impact with the ground. This high impact firmness gives good responsiveness, although it should be noted thatsometimes a very firm surface may not be as responsive as one would expect. It is moderately difficult to achieve a high level of cushioning on a very short sward, although the soil profile needs to be medium firm, well aerated and have deep rooting. A little organic matter is quite beneficial to ensure cushioning. However, elevated levels of organic matter can often lead to reduced grip and at significant levels give poor impact firmness.

Probably the most important factor is grip. Polo ponies turn very quickly, execute fast decelerations and accelerations. This means that the surface has to give confidence to the rider and the horse. A very dry soil profile may have less grip as the pony can slide on the dry top.

This is often relieved through sand dressings and through significant quantities of irrigation to create a slightly softer upper surface. Watering can be a problem as insufficient irrigation may only wet the surface and therefore create a shear layer.

Each site will have a different ideal moisture content for performance. It is not uncommon to find the centre sections of a polo field being firmer than the edges as this is where most of the play occurs and therefore targeted verti-draining through the middle of the ground is important.