Construction (soil profile)
The aim of natural grass sports ground construction is to produce a turf surface that is ‘fit for purpose’ for the designated activity. Construction standards for elite and premier surfaces are higher than those for local sports grounds.
Elite sports grounds
Elite sports grounds are constructed using an imported sand profile over a drainage layer with sub-surface drainage installed. Such construction is limited to elite venues, which are used for national and international grade sport or smaller areas such as golf or bowling greens.
Premier sports grounds
Premier sports grounds are constructed using an imported sand profile over a natural sub-base with sub-surface drainage installed. Such construction is used for high grade and state level sporting venues.
Local sports grounds
Local sports grounds are constructed using natural soils, where possible, with amendments incorporated if necessary. Generally surface slope is used for surface drainage. Where drainage becomes a problem sand slit drains can be incorporated to improve drainage.
For further information refer to sport specific requirements.
Natural grass species
The desirable characteristics of grass species for sports grounds are drought tolerance, wear tolerance, a consistent leaf density and good recovery rates.
Natural grass species can be divided into two types;
- Warm season (Kikuyu – Pennisetum clandestinum/Couch – Cynodon sp.)
- Cool season (Rye – Lolium sp./Fescue – Festuca sp.)
The warm season grasses have a creeping growth habit with horizontal stems growing above the ground (stolons) and below the ground (rhizomes) which provide good recovery characteristics. Warm season grasses can be established using seed, vegetative cuttings (stolons) or sods. Seed or stolons require several months and up to a year respectively to establish prior to use. Laying of sods, whilst more expensive, is quicker to establish and can be used within weeks of laying given the right conditions. The growing season is spring, summer and autumn with peak growth stages in the hotter summer months. Both Kikuyu and Couch provide a consistent leaf density, they are drought tolerant and have good wear tolerance. However, winter dormancy results in limited recovery from damage or wear during the cooler months, which is the period when grounds are subject to most wear.
Cool season grasses (Rye/Fescue) have an upright tufted growth habit relying on tillering from individual plants for growth and recovery. Cool season grass can be established using seed or sods. Seeded sports grounds require several months and up to a year to establish prior to use. Laying of sods, whilst more expensive, is quicker to establish and can be used within weeks of laying given the right conditions. The peak growth season is spring and autumn with reduced growth in winter. Whilst rye and fescue grass does not actually have a dormant period, they require significantly more water to sustain healthy growth in summer and are not drought tolerant. Where turf has declined due to wear, recovery requires over sowing as the individual grass plants must be replaced.
Kikuyu or Couch sports grounds can be over sown with rye grass to provide improved winter wear tolerance. However, it is necessary to eradicate the rye in spring. This practice is costly and is usually done only on premier sports grounds.
At a ‘local’ sports ground level the desired grass species are either Kikuyu or Couch grass. It is important that the grass quality is maintained to a high level with a consistent dense coverage going into winter dormancy so the grass can withstand winter wear. Whilst recovery from excessive wear in winter may be slow, the grass will recover during spring and summer. Where natural grass quality deteriorates this has an impact on surface quality with the development unstable, loose or uneven areas leading to divots and pot-holes resulting in twisting or trip hazards.
Natural grass turf maintenance
In order to maintain the grass turf to provide an acceptable, ‘fit for purpose’ facility, a sound turf maintenance program should be implemented aimed at maintaining turf health, soil structure, and surface levels. A turf maintenance program includes the following:
Turf should be cut with a cylinder mower weekly during spring and summer and fortnightly during the colder months when grass growth is slower. Height of cut should generally be between 15-25 mm for warm season grasses and 25-40mm for cool season grasses.
To maintain soil structure, de-compaction works using a mix of deep coring with hollow tynes in spring (verti-drain) and deep slicing (earthquake) in Autumn. Varying the de-compaction methods will ensure that a hard pan is not created within the profile.
Areas that suffer excessive wear may require sodding in order to maintain acceptable turf and surface quality. Areas such as goal squares and cricket pitch run-ups are particularly susceptible. Maxi-sods which are 600mm wide are preferred. Unless sods are grown on a sandy soil they will require coring with the addition of sand top-dressing to ensure drainage through any imported clay loam soil.
To maintain surface levels, sports turf should be top-dressed, concentrating on heavy wear areas such as the centre corridor and goals, in early spring following the winter competition season. Top-dressing material should be of high medium to coarse sand with hydraulic conductivity of > 100mm/hr and pH of between 6.0–7.0. Top-dressing rates are between 100–150 tonnes per hectare concentrating on the centre corridor and high wear areas. Top-dressing should follow sodding and coring to ensure the sand is incorporated into the root zone of the soil profile.
It is generally not necessary to implement a proactive weed, pest and disease control program for local sports grounds. Rather where weeds, pests or disease are identified specific action will be required.
Irrigation schedules over the summer months should replace soil moisture lost through evapotranspiration. A base irrigation schedule is developed using average climatic conditions and irrigation system application rates to ensure adequate irrigation is applied without wastage. The schedule needs to be adjusted for weather variations. As a guide the irrigation requirement for warm season turf using average climatic conditions in Perth is between 5,500kL-6,800kL per hectare.
Excessive thatch can be detrimental to turf health and should be minimised. The usage schedules will thin turf and thatch can be controlled with close mowing and sound irrigation programming. Where thatch levels become a problem dethatching or scarifying is required.
Healthy natural grass requires correct nutrition to provide the necessary food for the plant to grow. Laboratory soil tests should be done annually to determine soil nutrient status and enable amendment fertiliser program to ensure chemical balance within the soil. This is coupled with an ongoing maintenance fertiliser program providing the major nutrients of Nitrogen, Phosphorus and Potassium.
A natural grass sports surface provides an asset to a community which is alive and self-renewing given sound management. Being a natural surface it is subject to many variables and the quality of the surface is impacted by the quality of construction, maintenance regimes, weather and usage rates. Full lifecycle costings for specific natural grass sports surfaces for individual sporting codes are provided later in this report.  For further information on Natural Grass Surfaces Management refer to acknowledgments and further information.
History of synthetic turf
Synthetic turf was first invented in the mid 1960’s in America. It originally came into existence in the market place to replace natural grass that had difficulty growing in indoor stadiums. The Houston Astrodome was the world’s first fully enclosed stadium with a synthetic turf field. This field was not much more than green plastic indoor-outdoor carpet, however, it was praised for its visual appeal and playability and as a result, synthetic turf fields were soon under construction across America.
Despite a growing number of complaints from teams and players about various injuries occurring on the fields for most of the next decade, little change was made to the original turf design. Many of the USA stadiums that tried synthetic turf around this time, including the Houston Astrodome, all eventually returned to natural grass.2
However by the mid-1970s these first generation synthetic turf pitches (low-pile height, high-density of fibres) had improved to the point where a synthetic turf pitch was successfully used for the hockey tournament at the 1976 Olympic Games in Montreal. Made of nylon (polyamide) yarns, first generation pitches were coarse and capable of causing friction burns and wounds unless they were played on when they were wet - as per the hockey model. This model did not suit a number of sports including soccer, baseball and American football3 so the uptake of synthetic surfaces in these sports was slow.
Improvements in synthetic turf technologies continued over the next decade but it wasn’t until the early 1990’s that significant changes were seen, with the introduction of the third generation turfs. New, revolutionary improvements were happening. Various mixtures of silica sand and/or recycled tires (granulated crumb rubber) were now being incorporated into extremely well-drained synthetic turf fields. The overall playability of the fields was becoming more and more similar to natural grass surfaces.2
The use of a softer polyethylene based fibre and the ability of the surface to take a normal stud has resulted in it becoming an acceptable surface for sports such as soccer and rugby. The rubber infill, sometimes with a shock pad for added safety, have made third generation synthetic turf more acceptable for most of the sports where a player might occasionally slide, fall to the ground, or land from height. These third generation pitches are now becoming popular in Australia, and will increasingly be seen in the future being used for Australian Rules football and cricket (outfields), and for multi-sport usage.3
Types of synthetic turf
Type according to infill content:
Unfilled pitches were the first type of system implemented for sport. They had short pile height, were dense in quantity and had no infill material. They were often made of nylon, which meant the prototypes were often tough and abrasive. Partly due to the abrasiveness, watered unfilled surfaces were developed and have since been popular for elite levels of hockey.
With filled synthetic turf systems, the synthetic turf fibres or blades are fully supported or stabilised by the addition of a filling material, such as sand, clay and rubber granules, or a mix of sand and rubber granules. The sand and fibres combine to form the characteristics of the playing surface. Synthetic turf surfaces which are filled with sand only are generally suitable for hockey, tennis, lawn bowls, touch rugby, lacrosse, and soccer (training) and multifunction use.
Dressed systems are a derivative of the sand-filled system, and intermediate in their properties and playing characteristics between the traditional filled and unfilled carpets. They can have either:
- a shorter, denser pile than the standard filled system which are considered suitable for hockey, soccer (training), touch rugby, lacrosse and cricket (fielding practice).
- a longer pile which is suitable for soccer, rugby, Australian Rules football and cricket.
Types according to pile height:
Short-pile turf is made up of high-density short fibres (between 8-12mm in length) and is used predominantly for cricket pitches or for elite level hockey pitches. The unfilled hockey pitches have, until now, had to be kept wet to improve foot traction, ball speed and heat suppression.
Medium-pile turf (between 20-35mm in length) has traditionally been the hard-wearing sand-filled carpets used for hockey, tennis, lawn bowls and for training level activities in a variety of other sports.
Long-pile turf has long blades of fibre similar in height to some natural grass playing surfaces. The long fibres (between 40-65mm in length) provide cushioning and allow for a great amount of infill to be integrated into the pitch adding to the shock absorbency and force reduction characteristics of the ground, and plays more like grass. These fibres can be single fibre or multi-ended yarns (brush-like at the tip), and are proving to be popular for soccer, rugby, Australian Rules football/cricket and golf. The latest development with long-pile turf is the development of even longer fibre carpet (80-85mm, with approximately 60mm of infill material). This is being hailed as the first suitable synthetic turf system for athletics field events including hammer, shot put, discus and javelin.4
Maintenance practices for synthetic turf
It is often widely believed that synthetic turf fields require less ongoing maintenance than natural grass. Even though they do not require watering and mowing they do have an extensive maintenance protocol, particularly if used regularly for a multitude of sports events or for elite level sport.
Such maintenance is critical if the surface is to achieve its optimum performance, and full lifespan. Usually the installer’s guarantee or warranty will usually be conditional on the recommended maintenance requirements being carried out.
Maintenance practices differ depending on the type of synthetic turf surface installed and it is important to follow the manufacturer’s instructions and guidelines. Below is a list of common maintenance practices that are undertaken for synthetic turf.
Sweeping of leaves and other debris from the surface generally needs to be done weekly. If leaves, tree flowers, pine needles and other debris are left on the surface for any length of time they rapidly rot down and form a drainage-inhibiting skin within the surface which can encourage the growth of algae and moss.
Grooming the surface is a crucial operation aimed at keeping the mat and texture of the synthetic turf as even and uniform as possible, so as to prevent the deterioration of play characteristics, appearance and drainage properties. Grooming the surface through brushing and/or drag matting lifts the fibres at the surface. It redistributes evenly any sand or rubber that has been disturbed, and counteracts any compaction of the sand and any tendency to form an impervious surface skin which might impair drainage (filled surfaces only).
Moss and algae
In certain situations and in some seasons, algae or moss can become established on the surface. This only becomes a serious problem if it is allowed to become established. Prevention is more effective than cure, therefore, an annual application of moss-killer and/or algaecide is recommended. It is important to check the surface regularly for any signs of moss or algae growth and imperative that affected areas are treated as soon as they become present.
Weeds are not as prevalent in synthetic turf as they are with natural grass but, they do still appear from time to time. It is important to remove weeds as soon as they are noticed to prevent them from spreading. They can either be removed by hand or local areas of infestation can usually be treated with domestic weed killer, however, always check with the manufacturer before using any chemical sprays on the surface.
Most stains can be removed easily with a solution of warm (not boiling) water and a household detergent such as dishwashing liquid. Before attempting to remove heavy soiling and stubborn stains it is important to seek the surface supplier’s advice.
Joints and Seams
It is important to check all joints and seams on a regular basis and repair any failures promptly, before loss of any synthetic surface pile or risk to users.
Check and top-up infill levels (filled surfaces only)
High traffic areas such as penalty spots and short corners should be checked daily or weekly, but other areas of the ground infill levels should be checked monthly.
Many (but not all) manufacturers of third generation rubber-filled surfaces now recommend the use of powered brushing machines to ensure that the rubber particles remain mobile and the carpet fibres upright. This operation is recommended at least every 6 months.
Both sand filled, dressed and rubber filled surfaces may in time require a degree of deep cleaning. This will depend largely on the environment and usage levels and should only be performed if surface contamination is suspected, and then only by specialist contractors.5