Creating and Maintaining Athletic Fields
CREATING ATHLETIC FIELDS | INTRODUCTION | SCHEDULING | TYPES OF FIELDS | GRADING AND DRAINAGE | BUYING GOOD SEED | FALL SEEDING | SEEDING IN SPRING OR WINTER | SEEDING | MULCHING | IRRIGATING | PROMOWING | CONTROLLING WEEDS
ANNUAL MAINTENANCE | CONTROLLING TRAFFIC | AERIFYING | IRRIGATING | FERTILIZING | FERTILIZERS
Athletic fields are the toughest of all turf areas to manage. Season-long traffic in all types of weather can literally destroy a field, plus the playing schedule rarely allows for aggressive turf management practices that are absolutely essential to keep grass alive. Athletic fields must be constructed and managed properly to provide adequate turf, while minimizing the chance of injury to players. This booklet highlights several principles of construction and maintenance to help produce a field with good playability and emphasis on player safety. This booklet was conceived from studies done through the Agricultural Sciences Departments of Purdue University, University of Florida, University of Georgia and The University of Hawaii.
When planning construction of any turf area, the optimum target completion date is your end of warm weather season. This is because mid-August is the best time to seed cool-season turf grasses like Kentucky bluegrass, and Bermudagrass, which is the preferred grass to use for athletic fields depending on your location. A general rule of thumb would be, Kentucky for northern areas and Bermuda for southern areas. Therefore, when planning construction, work backwards from mid-August, allowing ample time for grading, settling, installation of irrigation and drainage, etc. to determine the start date. If seeding occurs in mid-August when growing conditions are exceptional, and irrigation is supplied, the fields will normally be usable within 12 months after seeding. On the other hand, if seeding occurs at any other time of the year, it could take 18 months or longer before the field is ready for play
The three basic construction types are native soil fields made of existing soil or topsoil brought on to the site, modified soils where the existing soil is modified with amendments such as sand or peat, and soil-less fields, which are essentially 100% sand. The most common type of field is the native soil field.
Without proper surface drainage, depressions will gradually develop that will hold water, make it difficult to maintain turf, and possibly risk injury to players. Though most coaches and players prefer to have a perfectly flat field, this is only possible with a very expensive soilless field. A 2% slope is preferred on most turf areas, but a 1% slope is acceptable on native soil fields given play considerations. For native soil fields, it is imperative to achieve a 1% slope from the center of the field to both sidelines. This will make a crown from 9 to 18 inches at the center of the field depending on the width. A less desirable alternative is to slope the field from one sideline to the other at a 1 to 2% grade. This will provide a “flat” field and allow surface drainage off the field, but is not as efficient as moving water from a field crowned in the center. Many will consider substituting subsurface drain tile lines for surface drainage. This is not recommended because water can be removed from a field more rapidly by surface drainage and will allow play within hours after a rain. Subsurface drainage is much slower and water will move off a field only within days or weeks after a rain. However, subsurface tile lines with open surface grates are important to install at the edge of a field to collect the surface drainage from the field.
After the sub grade is allowed to settle or is compacted, topsoil should be brought in over the rough grade. Ideally, four to six inches of topsoil is needed for optimum turf performance. After the topsoil is replaced, tile drainage with risers and/or catch basins should be installed on the sidelines of the field. In-ground irrigation should also be installed at this time. Though in-ground irrigation is relatively expensive to install, it is practically required to maintain playable soccer fields in Indiana.
After drainage and irrigation installation, the topsoil will usually need to be tilled to break up clods and to create a uniform seedbed. Avoid tilling soils that are too wet because it will smear the soil and decrease drainage. Overly aggressive tilling should also be avoided because it will create a fluffy and fine particled soil that is prone to compaction and poor drainage and aeration. Inclusion of soil amendments during tillage provides marginal effects and thus generally is not recommended.
Prior to final grading, allow adequate time for soil to settle to avoid uneven turf later. Irrigation or rainfall will accelerate settling. During this time, a soil test should be taken from the site, which will determine fertilizer recommendations for the area. Correct any deficiencies in nutrients or pH by following the recommendations on the soil test report. Final grading follows tilling and serves to smooth and level the surface. Hand rakes, sand trap rakes, or other tools are used to establish the seeding surface. A final shallow raking should occur immediately before seeding to prepare a good seed bed. After the seedbed is prepared, apply a starter fertilizer.
It is important to purchase high quality grass seed for any turf area, but it is especially important for athletic fields. High quality seed will probably be some of the most expensive seed available. However, the cost of seed is minuscule compared to the amount of money spent on maintaining the field for the next 20 years or the lifetime of the field. The best way to purchase high quality grass seed is to contact a reputable company who has experience providing seed for athletic fields. Additionally, the ability to understand seed labels is critical when selecting seed to determine the quality.
As mentioned previously, the best time of year to seed a soccer field is in the late summer to early fall. Adequate soil moisture, warm soil, and limited weed pressure allow for excellent seedling growth. The more time the field has to establish itself before summer, the better. Between August 15 and September 15 is optimum seeding time in the northern half of Indiana; from September 1 to September 30 is optimum in the southern half of Indiana. It is critical to seed as early as possible within these windows. Even when seeding within these windows, waiting one week later to seed may mean the stand will take two to four additional weeks to mature. Establishment in the spring is possible but not as effective as fall seeding.
Seeding in the spring is possible, but only if an automatic irrigation system is in place to provide adequate water for the seedlings through the first summer. It is important to seed as early in the spring as possible to maximize the competition of turfgrass over crabgrass. Dormant (winter) seeding or early April seeding is preferred. Dormant seeding occurs when seed lies dormant until the soil temperatures warm in April or May. Depending on your location, dormant seeding can be done as early as Thanksgiving and as late as March. The benefit of dormant seeding is that as the soil heaves and cracks during the winter, crevices (honeycombs) are created for the seeds, which create ideal germination conditions. Additionally, dormant seeding is easier to schedule than spring seeding, because spring rains make it difficult to seed after March. Though seed-soil contact is important regardless of seeding date, it is especially important when dormant or spring seeding. Irrigate often as soon as temperatures favor germination (soil temperatures above 55°F). As root systems develop, gradually reduce frequency but increase duration of irrigation. Continue irrigation throughout the summer until an adequate root system is established.
Seed should be applied using a drop spreader, because rotary spreaders do not disperse the seed uniformly. However, there are no spreader calibration guides for turfgrass seed. The easiest way to apply seed uniformly is to set the spreader adjustment very low, sow one half of the seed in one direction, and then sow the other half at right angles to the first direction of seeding.
It might take three or more passes over the field in a single direction, but it is well worth the time to get a uniform seeding. Hydroseeding can be used where seed is combined with paper-based mulch and sprayed onto the field. Though this is more expensive than traditional drop seeding, it delivers excellent results with good germination and the added benefits of mulch. Contact a local reputable landscaper for hydroseeding.
Mulching or covering is generally not recommended for an area as large as an athletic field. However, since mulch conserves water, it is important to mulch fields that cannot be watered two to four times daily during establishment. One bale of clean (weed-free) straw per thousand square feet will give a light covering that will not have to be removed after germination. Oat or wheat straw is strongly preferred over hay or soybean stubble. Do not apply too much mulch, which will shade seedlings and have to be raked off later. Apply the mulch very lightly so you can still see approximately 50% of the soil through the mulch layer.
Seedlings are very susceptible to drying out, and the seedbed should not be allowed to dry. A newly seeded field will need to be irrigated two to four times daily depending on the weather. This is why automatic irrigation is extremely important. When irrigating (each time), enough water should be applied to moisten the top one-half to two inches of the soil profile, but avoid over-watering and saturating the area. Once the seedlings are two inches high, gradually reduce the frequency of irrigation and water more deeply. After the turf has been mowed two or three times with a reel type mower, deep and infrequent irrigation to the depth of the root system is most effective.
Mowing a new field will encourage the turf to fill-in quickly. Proper mowing practices will also promote adequate rooting and surface density and uniform growth. Mowing should begin when the first few seedlings are tall enough to mow. You may only mow 10% of the plants in the first mowing, 20-30% of the plants in the second mowing, and so on. Most people wait too long to mow a newly seeded field, so mow early and often with a reel type mower. Mow 2.0-2.5 inches and as always, never remove more than 1/3 of the grass blade at any one mowing. Mowing is important to maintain the health, playability, and aesthetics of a athletic fields. Mowing height of a Kentucky bluegrass soccer field should be approximately 2.0-2.5 inches, 0.75 inches for Bermudagrass. Mowing lower than these heights on most fields will put added stress on the plants and will decrease vigor of the plants and playability over the long term. Mowing below the optimum height restricts root growth, favors weeds, and increases susceptibility to damage from insects, disease, drought, and traffic.
Mowing frequency depends on how fast the grass is growing. Some fields may need mowing two or three times per week during spring and fall and only once every two weeks during summer. Mow frequently enough so as not to remove more than 1/3 of the leaf blade in a single mowing. For instance, if you are mowing at two inches, mow before the grass reaches three inches tall. If the grass has grown too tall, raise the mowing height and gradually lower it back to the original height over the next few mows. Avoid mowing during midday when temperatures are above 90o and the soil is dry because you may damage the turf. If you must mow during a hot and dry period, wait until temperatures moderate in the early morning or late evening.
Rotary mowers are not recommended for use on athletic fields. Most rotary mowers only cut well at mowing heights of 3 inches and above. Reel type mowers such as the ProMow Trophy or Gold Series mow best at two and a half inches and lower.
When mowing, due to the large cut that ProMow offers, you should consider mowing in both directions, it won’t take much longer and your grass will be trained to grow straight and very rigid. Your ProMow mower blades must be sharp a sharp blade results in a cleaner and healthier cut, leaving a more attractive and healthy field.
Clipping removal is generally not recommended on most areas including athletic fields. Clippings do not cause thatch, and returning clippings will recycle valuable nutrients to the soil thereby reducing fertilizer requirements.
There is little weed pressure in the fall so weed control may not be needed for fall seeding. If broadleaf weeds such as clover and dandelion become a problem later in the fall, they can be easily controlled with a broadleaf herbicide application in October or November, after the third or fourth mowing. Annual grasses such as crabgrass can be easily controlled the first year with pre-emergence herbicides applied in the spring. In seeding made very late in fall, winter, or spring and the field is not fully established by spring, avoid applying a pre-emergence herbicide in early spring because it may damage late-developing seedlings. In this case, consider using a post-emergence crabgrass herbicide later in summer to control crabgrass.
Constant play on athletic fields will cause the turf to deteriorate and become un-playable and possibly dangerous to the athletes. Strict traffic management is the most effective tool in maintaining playability of fields. Rotate play to schedule maintenance such as aerification and overseeding to limit turf damage and aid in recovery. Consider preventing play for three or more growing months each field depending on the time of year, amount of play, and extent of damage. Keep strict practice areas to limit damage on game fields. Consider movable goals, benches, bleachers, and fences to help further limit damage.
Aerification is the mechanical removal of soil cores and may be the most important turf management practice on soccer fields. Aerification relieves soil compaction, improves water and air movement into the soil, increases rooting, and greatly improves turfgrass health.
Aerification is most beneficial in compacted areas with intense traffic such as goalmouths, the centers of fields, and sideline areas. Whenever aerification is done on a soccer field, it should be combined with seeding to help maintain dense turf. This will be discussed more in the overseeding section.
Aerification is most beneficial when the largest tines or spoons available are used; penetration is 2 to 4 inches deep, and when 20 to 40 holes are punched per square foot. Aerifiers with reciprocating arms are the most effective. Aerifiers that roll behind tractors are less effective because they do not penetrate deep enough nor punch enough holes per square foot. Most aerifying machines available at rental agencies may not punch enough holes per square foot on a single pass, thus multiple passes will be needed to achieve the 20 to 40 holes/ft2. Cores can be broken up and dispersed following aerification with a dragmat. Practices such as slicing or spiking remove no soil and are not considered aerification. The purchase of a large reciprocating arm aerifier should be included in the budget because aerification will be needed often. There are professional aerification services that can be hired to aerify athletic fields providing a viable alternative to purchasing your own aerifier.
Aerification should be performed as often as possible on an athletic field and should be done preferably when the turf is actively growing. However, if playing schedules do not allow for aerification during the season, aerifying at any time of the year is better than not aerifying at all. Kentucky bluegrass or tall fescue should be aerified at least once in the fall (September) and once in the spring (April). Bermudagrass should be aerified at least once in June or July when it is actively growing.
To maintain a healthy, actively growing turf capable of recovery from damage, it is essential to water a field during dry periods. This is especially important on a field that receives regular overseeding or sprigging because seedlings are present in the field almost all year long. Seedlings cannot withstand moisture stress because they do not have a well-developed root system capable of extracting water from a large area in the soil. Bermudagrass fields generally have much lower water requirements than Kentucky bluegrass fields. However, ample water is needed to encourage recovery and establishment of new Bermudagrass sprigs. The same principles for irrigating cool season grasses hold true when irrigating warm season grasses.
The frequency of watering will vary from site to site and should be determined by the appearance of the turf. This can be determined because the first signs of water stress in a turfgrass stand are a bluish-green color, and footprints remain in the turf after walking across it. Ideally, the turf should be watered at this point. As the degree of water stress increases, the turf will wilt and develop a grayish-green color. Turf that has wilted should be watered without delay. Wilted turf will recover very rapidly following watering. Severe drought stress will cause the turf plants to cease growing, and the leaves will turn brown and possibly die. If soccer fields are allowed to wilt or turn brown, do not allow play on the fields until they can be irrigated and the turf recovers. Though this might take up to two weeks, it will prevent severe damage that will result from traffic on wilted or dormant turf.
Most fields will need from 1 to 1-1/2 inches of water per week depending on weather, soil type, etc. It is best to apply this amount of water in a single, thorough soaking, or two equal applications of water three to four days apart rather than in light irrigations every day. The soil should be wetted to the depth of the deepest root.
Schedule irrigation as to not interfere with play and to allow ample infiltration and drying prior to use. The ideal time to irrigate a soccer field is from 4:00 to 8:00 a.m. At this time, water pressure is usually high, there is little distortion of the watering pattern by wind, the amount of water lost to evaporation is negligible, and the field will dry by the time it is used later in the day. The second best time to water is from 8:00 to 12:00 p.m. Usually, distortion from the wind is not a problem at this time and loss from evaporation is slight. A major problem may be lack of water pressure for those using municipal water systems. A potential problem caused by watering in the early evening hours may be greater incidence of disease. This problem can be reduced by watering only when the turf needs water and by watering infrequently but deeply. Watering an established turf during midday is not very effective. A large amount of water is lost through evaporation, making it difficult to thoroughly wet the soil. Although not recommended, midday watering does not cause the turf to burn as once thought.
Athletic fields need to be fertilized to maintain color, density, and vigor. Athletic fields also need to be fertilized slightly more than other turf areas to encourage growth and overcome the constant wear and tear. Fertilizer needs may vary due to:
- Weather: A rainy summer will stimulate growth and will usually necessitate more annual fertilizer than a dry summer. The same holds true for an irrigated field versus an un-irrigated field.
- Soil type: Turf grown on a very sandy or a very heavy clay soil will need more fertilizer than turf grown on a silt loam soil. Soil type and pH will have a large effect on the amount of phosphorus and potassium that needs to be applied.
- Age and quality of existing field: A new field will need more fertilizer for the first few years to enhance density. Improving a neglected or thin field that needs significant overseeding or sprigging may also require more annual fertilizer for the first few years.
All fertilizers will have a series of three numbers displayed prominently on the label. These numbers represent the percentage by weight of Nitrogen, Phosphorus and Potassium. For instance, a 24-4-8 fertilizer will have 24% Nitrogen, 4% Phosphorus, and 8% Potassium. Though all three elements are important in maintaining a healthy turf stand, Nitrogen will cause the greatest response. Nitrogen fertilizers come in two basic forms: quick release (soluble) nitrogen and slow release (insoluble) nitrogen. Quick release nitrogen normally causes a response in a week or less, whereas slow release nitrogen will cause a response in three to 10 weeks or more. Quick release nitrogen is inexpensive and may burn leaf blades if applied improperly. Slow release forms tend to be more expensive, but will rarely burn leaf blades even when applied at temperatures above 85°. Both forms can and should be used on fields.
Fertilizing with phosphorus and potassium is also important in maintaining a healthy field. The best way to determine how much phosphorus and potassium to apply annually is to follow the recommendations of a soil test. In lieu of a soil test, a general recommendation is to apply 1/4 as much phosphorus and 1/3 as much potassium as nitrogen. For instance, if you apply 40 pounds Nitrogen per year, you should apply 10 lb Phosphorus and 30lb Potassium per year.
On Kentucky bluegrass or tall fescue fields, it is best to fertilize lightly in spring and early summer, little to none in summer, and heavy in fall. A heavy fall fertilization program will produce the healthiest turf throughout the year.