The essentials of such a program are:
- That it is managed to produce tough grass with maximum wear resistance.
- That it be designed to maintain high density to resist weed invasion and encroachment of undesirable grasses.
- That it encourage deep rooting to provide good anchorage and firm footing.
- That mowing height be adjusted to both grass requirements and playing demands.
- That fertilizing and watering be done at such times and in such a manner as to provide steady growth with maximum quality.
- That considerations be given to the endurance limits of the turf in scheduling use of the field.
- That provision be made for repair of injuries due to wear or other causes.
The following outline of maintenance operations and methods is designed to meet these requirements.
Grass should be cut often and at a height adjusted to the predominating grass in the mixture. Kentucky bluegrass, fine fescue, improved ryegrass, or mixtures of these grasses should not be cut to a height of less than 1½ to 2 inches. Tall fescue should not be cut to a height of less than 2 to 2½ inches. Frequency of mowing is governed by the growth rate of the grass. Cutting should be done whenever grass grows three-quarters to 1 inch above the cutting height. No more than one-third of the total leaf surface should be removed at any mowing. If this practice is followed, it is not necessary or desirable to change the mowing height at any time. Bermudagrass should be kept one-half inch high by frequent mowing. When cut higher it becomes spongy and loose, and does not provide a good footing or a dense turf. Zoysia should be cut at one-half to three-fourths inch.
Irrigate only when the grass shows signs of wilting and discoloration because of lack of water. Equipment should be adjusted to apply water only as fast as the soil will absorb it. A soil sampling probe can be used to determine the rate and depth of moisture penetration. Sprinklers should be operated until water has penetrated to a depth of at least 6 inches. Traveling types of sprinklers will provide more uniform water distribution than stationary kinds, unless the latter are checked often. Periodic aerations will speed up water penetration and usually results in more efficient water use.
Constant trampling often causes a compact, impermeable surface layer of soil. This condition can be aggravated by mowing, rolling, or using other heavy equipment when soils are wet. Compaction cannot be avoided under such conditions, and when it develops, grass roots are injured because of insufficient moisture and air to assure normal functioning. In addition, it becomes more difficult for water and fertilizer to penetrate the soil. Sand fields, especially when relatively new, generally require less aeration than soil fields. However, as sand fields mature, organic matter build-up may develop in the surface 2 to 3 inches and increased aeration will be required.
Various types of aeration tools have been devised to break through the compacted soil layer mechanically and remove a soil core. Size of openings made by these machines varies with the diameter of the hollow tines or spoons used. For athletic fields such openings should be about three-quarters to 1 inch in diameter. Equipment having solid tines or spikes should not be mistaken for aerating equipment. Aerators always remove a soil core, whereas solid tine spikers do not. Spikers actually increase soil compaction as the movement of the soil to all sides by the penetration of the solid tine forces the soil into a denser mass.
Fields should be aerated systematically a minimum of three times per year. Heavy aeration (six to eight times over the area) in the spring, prior to fertilization and/or overseeding, is recommended, followed by light aeration (one to three times) in late summer or early fall, prior to fertilization. Aeration at these times should be followed by dragging with a chain drag, flexible tine harrow, or a section of chain link fence. At the close of the fall playing season, again aerate at the heavy rate but do not drag the area open, freezing and thawing of moisture in the holes will improve the effectiveness of aeration. Where a field is in constant use, it sometimes is necessary to aerate several times during the season. Where areas receive heavy and frequent use, light aeration every 10 days to 2 weeks during the playing season may be beneficial. A good rule to follow is to aerate whenever the turf begins to show the effects of soil compaction.
The lime requirement of soils should be tested every 3 or 4 years. This service is available at a minimal cost through the Agricultural Extension Service or private soil testing laboratories. Lime should be applied whenever the soil shows a pH of less than 6.2 or a lime requirement of more than 1,000 pounds of limestone per acre. Applications can be made at any time. Usually it is most effective and convenient to apply limestone in late fall following thorough aeration or during the winter on frozen turf. Ground agricultural limestone is the recommended form of lime to use. Where soil tests show a deficiency of magnesium, ground dolomitic limestone should be used.
The maintenance fertilizer program should be based on complete soi test results. Required amounts of phosphate and/or potash vary greatly with the natural soil fertility, establishment fertilization, and previous maintenance fertilization. Most athletic areas will require two complete fertilizer applications per year although some soil fields may require only one complete fertilizer application supplemented with one or more nitrogen applications. Sand fields due to their low nutrient holding capacity, may require four or more fertilizer applications per season. Occasionally, fields having very high phosphate and potash levels will require only nitrogen applications. When economics dictate a single application of a complete fertilizer, cool season grasses such as Kentucky bluegrass, fine fescue, tall fescue, and perennial ryegrass benefit most by a late summer to early fall application. Bermudagrass and zoysia should receive the application in the spring. Where soil tests show low levels of phosphate and/or potash, it may be necessary to make additional supplemental applications of phosphate, potash, or phosphate-potash fertilizers one or more years. These applications should be applied in the fall until soil levels are satisfactory.
Rates of application of the complete fertilizer will vary with the species or variety of grass, the soil fertility level, the soil type, the fertilizer grade, and the type of nitrogen contained in the fertilizer. Cool season grasses require the major plant nutrients (nitrogen, phosphate, potash) in an approximate 2-1-1, 3-1-1, or 4-2-1 ratio. Fine fescue, common Kentucky bluegrass, and turf type perennial ryegrasses require approximately 3 to 4 pounds of nitrogen, 2 pounds of phosphate, and 2 pounds of potash per 1,000 sq ft per season.
A fertilizer bag may carry the following label:
Total Nitrogen - 10%
4% Water Insoluble Nitrogen
Available Phosphorus - 5%
Water Soluble Potash - 5%
In the above label example, the 10 percent represents the total percentage of nitrogen contained in the bag. The 4 percent represents the total percentage of nitrogen in the bag that is water insoluable (WIN). The percentage of the total nitrogen that is water insoluable must be calculated from this label information. This value can be obtained by dividing the percentage of water insoluable nitrogen indicated on the label by the total percentage of nitrogen contained in the bag (also indicated on the label) and multiplying by 100. In this case 4 ÷ 10 times 100, or 40 percent of the total nitrogen is water insoluable. A turf-grade fertilizer normally is considered to be one that contains 30 percent or more of the total nitrogen as water insoluable nitrogen. Thus, this fertilizer meets the requirements of a turf-grade fertilizer. If the grade were 20-10-10, having 4 percent water insoluable nitrogen in the bag, the percentage of the total nitrogen that is water insoluable would be 4 ÷ 20 times 100, or 20 percent, and the fertilizer would not meet the requirements.
The ideal fertilizer program provides uniform growth over the entire growing season. Although this ideal is never fully reached due to temperature and moisture fluctuations, the types of nitrogen-carrying materials in a fertilizer are important in moving toward this ideal. Basically, nitrogen materials are divided into two broad groups — quickly available and slowly available.
The quickly available materials are water soluable, and the nitrogen is immediately available to the plants provided there is adequate soil moisture. Results are a sudden flush of growth and a rapid depletion (2 to 6 weeks) of the available nitrogen. Thus, it will be necessary to make frequent light applications of these materials in order to obtain uniform growth over a long period of time. Quickly available nitrogen materials include ammonium sulfate, ammonium nitrate, nitrate of soda, ammonium phosphate, calcium nitrate, urea, and others.
Fertilizer containing quickly available sources of nitrogen should be used with caution. Due to the danger of “burning” with these materials, application rates must be reduced and application frequency increased in comparison to fertilizers containing slowly available nitrogen.
Slowly available nitrogen materials release a major portion of their nitrogen over relatively long periods. These materials depend upon microbial decomposition alone or physical and/or chemical processes in combination with microbial activity to provide nitrogen in a form available to the plant. The activity of soil microorganisms is highly dependent upon soil moisture and temperature conditions. Under high temperature and adequate moisture supply, microbial breakdown of these materials is accelerated. Under conditions fo high temperature and low moisture, or low temperature, the breakdown will be much slower. Materials dependent on physical processes (such as hydrolysis) for nitrogen release are relatively unaffected by temperature but are highly dependent on adequate soil moisture. Within the slowly available sources of nitrogen there are natural organic materials and synthetic organic materials dependent upon microbial decomposition alone, and synthetic organic materials and coated nitrogen products dependent upon physical and/or chemical processes in combination with microbial activity.
Natural organic materials include activated or processed sewage sludge, animal and vegetable tankage, manures, soybean meal, and cottonseed meal. Because these natural organic materials vary greatly in their chemical composition, there will be a wide variation in the rate of breakdown, although all of them will release their nitrogen at a slower rate than the quickly available nitrogen sources.
Uniform compounds are synthetic materials made by the chemical union of urea and formaldehyde. Within a given ureaform material is a series of chemical compounds with varying degrees of solubility and resistance to decomposition. As the soil bacteria decompose these materials, the more easily decomposed materials break down first, followed by each successive compound. Thus, a small amount of nitrogen is being released constantly over a relatively long period of time. This permits the user to make heavy applications of these materials at rather infrequent intervals. Methylene ureas, also made by combining urea with formaldehyde, contain some slow release nitrogen but do not qualify under the generally accepted definition of a turf grad fertilizer. Care must be take not to confuse urea (quickly available nitrogen) with ureaform (slowly available nitrogen).
IBDU (isobutylidene diurea) is an example of a synthetic material that is dependent upon hydrolysis to release its nitrogen. IBDU has extremely low solubility in water. As it is relatively unaffected by temperature, it has the advantage of releasing nitrogen, provided adequate moisture is available, during periods of cool weather when microbial activity is limited. IBDU also has been shown to be more efficient (more of the nitrogen is recovered by the plant in the season of application) then ureaform.
Sulfur-coated urea is a slow release nitrogen product made by coating urea prills or granules with molten sulfur and a sealant such as wax. The rate of release of the nitrogen is determined by the thickness of the sulfur coating. By using a product containing urea particles with varying thicknesses of sulfur coatings, nitrogen release can be obtained over a relatively long period (8 to 10 weeks). Other coated products use plastic resins, waxes, asphalt, and latex as the coatings but none has shown value for turf fertilization.
Proper liming is essential to a sound fertilization program. Lime should be applied in accordance with a soil test. Proper liming creates a favorable soil environment for plant growth and keeps plant nutrients available for plant use. Liming, therefore, provides the most efficient use of applied fertilizer materials.
As a result of excessive rainfall or other unusual growing conditions, nitrogen supply may be depleted prior to the normal refertilization time. This is especially true of sand fields having low nutrient holding capacity. Under these conditions, supplemental nitrogen applications at light rates may be beneficial to the turf. This may be most easily accomplished by applying urea at a rate of 85 to 100 pounds per acre as indicated by the needs of the grass.
Fertilizer guidelines are based on a complete fertilizer having an approximate 2-1-1 ratio or a straight nitrogen-carrying material, and on an application rate of approximately 3 to 4 pounds of nitrogen per 1,000 square feet per season for soil fields, or approximately 5 pounds of nitrogen per 1,000 square feet per season for sand fields. These guidelines are for average soil conditions and must be supplemented with additional fertilizer where soils are deficient in phosphate and/or potash.
Lesser rates of nitrogen are suggested in the spring than in the fall to avoid over stimulation of the grass in the spring which may result in an increased incidence of leafspot damage.
Guideline fertilization programs follow:
|Nitrogen source||Time of Application
|Late spring||Early summer||Late summer||Early fall|
|Pounds of N-P2O5-K2O per acre applied|
|Additional P2O5 and/or K2O should be applied where soil test indicates need.
|50% or more of the N derived from a slowly available source
|25% to 49% of the N derived from a slowly available source
|water soluble N
|Nitrogen source||Time of Application
|Late spring||Early summer||Late summer||Early fall|
|Pounds per acre applied|
|Natural organic (5-7% N)
|Ureaform (38% N)
|IBDU (31% N)
|Sulphur coated urea (SCU) (approx. 32-37% N)
|Urea (45% N)
|Nitrogen source||Time of Application|
|Late spring||Early summer||Mid-summer||Late summer||Early fall|
|Pounds of N-P2O5-K2O per acre applied|
|* As fields mature (3 to 5 years), the build-up of organic matter will increase soil microorganism activity and natural organic N or ureaform N may be used.
|* 50% or more of he N dervied from IBDU or SCU
|* 25-49% of the N derived from IBDU, SCU, or methylene urea
|Water soluble N||44-22-22||44-22-22||40-20-20||44-22-22||44-22-22|
Properly prepared bid specifications are necessary to ensure obtaining the desired fertilizer. This is especially true if slowly available nitrogen is preferred. Specifications should state clearly the grade, amount, and type of nitrogen contained in the fertilizer. To state that “fertilizer shall be a 10-5-5 or equivalent containing 50 percent organic nitrogen” or “fertilizer shall be 10-5-5 or equivalent containing 50 percent organic” is inadequate. Such specifications would include fertilizers formulated with urea (legally listed as organic nitrogen but which behaves like a quickly available inorganic material) which would not give the desired slow release.
Proper specifications should state “fertilizer shall be a 10-5-5 or equivalent having 30 percent or more of the total nitrogen as water insoluable nitrogen (WIN) or controlled release nitrogen (CRN) derived from a slowly available nitrogen source (natural organic material, ureaform compound, IBDU, or sulfur coated urea).”
It is impossible to prevent damage to athletic field turf. Weeds, clover, and other undesirable plants come into the injured areas. Unless these are removed promptly they prevent the good grasses from healing the scars. Chemical treatments usually are the most effective means of control.
Broadleaf weeds such as dandelion, broadleaf plantain, and narrow leaf plantain (buckhorn) can be controlled with 2,-D. Clover, knotweed, chickweed, and sorrel are susceptible to dicamba. Crabgrass can be controlled with any of several preemergence or postemergence herbicides. For the latest recommendations on weed control in turfgrass areas obtain the latest Agricultural Extension Service publication on turfgrass weed control fromm your county Extension office.
Follow directions on the herbicide manufacturers’ labels for rates of applications and use care in handling all materials and containers.
Diseases and insects
A number of diseases and insects may cause serious injury to turfgrasses. The first step in a control program is to determine the cause of the trouble. Identification, particularly of diseases, often is difficult. Since many diseases and some insects require specific treatment, diagnosis of the cause of injury should be checked with a competent authority, such as the county Extension agricultural agent, before expensive control measures are undertaken. Effective control measures have been developed for many diseases and insects. For the latest recommendations, contact your county office of the Agricultural Extension Service.
There is a limit to the amount of traffic that even the best managed turf can withstand without excessive injury. This must be recognized if frequent costly repairs are to be avoided. Some of the things that often can be done to reduce injury are:
- Schedule a minimum of use when fields are wet.
- Rotate play areas, where size of area permits, to provide a resting and recovery period for turf showing the effects of wear.
- Avoid concentrated trampling, such as practicing band formations, whenever possible.
- Limit or withhold use of newly seeded areas until a mature turf has developed.
- Avoid use of the field in the spring until the turf has had an opportunity to recover from winter dormancy.
- Keep off the area when there has been surface thawing of frozen turf.
General repair and renovation
A well designed repair and renovation program should be a standard part of athletic field turfgrass management. The method must be adjusted to the amount of damage to the field and the manner in which the field is used.
Repair by seeding with permanent grasses.
Practically all athletic fields, especially football and soccer fields, will require some repair following the playing season. Fall sports normally end too late to overseed fields at the close of the playing season. Where turf loss is less than 50 percent with a minimal amount of bare spots, overseeding can be used as a means of repair.
- Best overseeding results will be obtained using a blend of turf type perennial ryegrasses.
- Overseed on “honeycombed” soil from late February through late March. Best results are obtained if the soil is freezing at night and thawing during the day. Apply seed during the early morning when soil is frozen. Apply total amount of seed to be used in several applications 4 to 5 days apart rather than in one application. Total seeding rate should be one-half to three-fourths the normal seeding rate.
- If overseeding is not done on the “honeycomb”, it can be done later in the
spring when weather conditions permit use of machine equipment.
After cleaning up all winter debris, aerate field eight to ten times with a spoon type aerator.
Broadcast seed or cut seed into soil with a turf type disk seeder. Drag field with chain-link fence, a flexible tine harrow, or similar equipment to break up soil cores and work seed into soil.
- Time of overseeding may vary with field usage. To maximize overseeding results, fields used primarily for spring sports should be overseeded in late summer or early fall. Fields used primarily for fall sports should be overseeded in the spring.
- In some instances athletic fields, especially football fields, are overseeded regularly during the playing season. This is most often done if there is a 2 week non-use period as a result of an “away” game. Two methods of seeding are used. Some superintendents simply apply the seed just prior to a game with the assumption that cleats will force much of the seed into the soil. Others feel that a light aeration immediately after a game followed by overseeding is beneficial. Normally, seeding is done with an improved turf type ryegrass. It must be realized that the amount of permanent survival is extremely low and that this approach may not be economically feasible in many instances.
Repair by reseeding with permanent grasses.
Reseeding as opposed to over-seeding may be necessary where large areas of the field are completely bare. This is especially true of football fields between hash marks and around the goal areas of soccer, field hockey, and lacrosse fields. In many cases this method is practical only when the field is out of play long enough to permit new seedlings to become fully established. This may require 4 to 6 months for cool season grasses and 3 to 4 months for warm season grasses.
- Disk or otherwise till areas to be reseeded to a depth of 4 inches or greater.
- Add sufficient topsoil to fill in any low spots. Topsoil should be equal in quality or of better quality than the existing soil.
- Apply ground limestone according to soil test if needed.
- Apply basic fertilizer (phosphate and/or potash) according to soil test.
- Refill and finish grade for seeding.
- Seed with one of the seed mixtures suggested for establishment. Choose a seed mixture similar to any existing turf. Seed at the full establishment seeding rate. If the seeding is made in the spring and the field must be used in the fall of the same year, seeding should be made with a blend of 100 percent turf type perennial ryegrasses. Apply seed with broadcast, cultipacker, or similar seeder or by hydroseeding.
- If broadcast seeder is used, drag or lightly rake seed into one-quarter inch of soil. Firm with light roller to put seed in close contact with the soil.
- Mulch with suitable mulching material.
Repair by plugging and sodding.
This may be the only satisfactory method of maintaining an adequate turfgrass cover on heavily and continuously used fields. Its essential features consist of setting sod plugs into small damaged areas of not over 6 inches in diameter and patching larger areas with sod from a nursery maintained for this purpose.
A hole cutter, such as is used for setting cups on a golf course, is the best tool for plugging. A 3-inch-deep plug is cut out of the area to be repaired and replaced with a sod plug from the nursery.
Sodding can be done at any time during the growing season if the turf is handled carefully and watered properly. The first step is resodding is to remove the old turf from the damaged area. Small sections can be lifted with a hand tool. Some type of power sod cutter should be the same as outlined for new seedings. The prepared surface should be firmed by light rolling. If the soil is dry, apply water in a fine spray to dampen it just prior to laying the sod. Sod pieces of any convenient size can be used. Where large areas are involved, strips 4 to 6 feet long by 12 to 18 inches wide are very satisfactory. Sod should be cut as this as possible. A well-kint Kentucky bluegrass of fine fescue sod can be cut so that not more than half an inch of soil is present below the crowns of the grass plants. Bermudagrass sod can be cut even thinner. Sod should be laid as soon as possible after cutting. If it must be held for more than 1 to 2 days, particularly when temperatures are 70 to 75 degrees, it should be unrolled and kept watered until used.
Sod can be purchased from commercial growers or can be grown in your own sod nursery when land is available. The sod nursery is by far the most economical and satisfactory source of material. It assures turf composed of the desired grasses and the prompt use of cut sod. A nursery of 10,000 square feet supplies enough sod to meet average renovation requirements.