A dense, wear-resistant sod is essential on athletic fields and play areas to provide playing safety, good footing, and a pleasing appearance. Production and maintenance of such a turf depend on the kinds of grasses used, proper design and construction, good soil drainage, proper seedbed preparation, adequate fertility, and a maintenance program which recognizes the special nature of the care involved.
Prepared by John C. Harper II, professor emeritus of agronomy.
Types of Fields
Three basic types of construction currently are used for athletic fields.
These include fields constructed from the natural soil existing at the site, or in part from topsoil hauled to the site; fields constructed from modified soil; and fields constructed from a soilless medium (essentially 100 percent sand).
Natural soil fields
The majority of athletic fields constructed today, at least at the high school, club, and small community levels, are natural soil fields. This is because natural soil fields are the least costly to establish initially. Although some athletic field sites in Pennsylvania may have sandy loam soils, most sites will have much heavier soils. These heavier soils, due to their high base exchange capacity, hold adequate nutrients resulting in relatively simple maintenance fertilization programs. They also have high water holding capacity, eliminating the absolute necessity but not the desirability of having an irrigation system.
Natural soil fields often are plagued with internal drainage problems.
These fields must be crowned with a turtle-back crown to ensure adequate surface drainage. Because these soils compact readily, especially in the surface inch, internal drain tile within the playing area normally is not recommended; but perimeter tile lines with open catch basins are required to rapidly remove the concentration of surface water coming off the field crown. Crowned fields are not suitable for multiple sports because of the difficulty they cause in controlling the ball in such sports as soccer and field hockey.
As turf thins during the playing season natural soil fields may become quite muddy during periods of heavy rain. Although it is not unusual to incorporate a small amount of organic matter into the surface of a natural soil field, such soil is not considered to be modified soil construction.
Modified soil fields
Those fields that have had a coarse physical amendment, such as sand, mixed uniformly with the existing soil are modified soil fields. Most Pennsylvania soils require 50 percent or more coarse amendment be added to make a marked physical improvement of these soils. Properly modified soils will have better internal drainage and less susceptibility to compaction, compared to unmodified soils. Nevertheless, modified soil fields require crowning of the field, as well as perimeter tile lines with open catch basins. In addition, the subgrade also should be crowned and a 6-inch stone blanket placed between the subsoil and the modified soil to facilitate water movement from internal drainage to the perimeter tile lines.
The particle size range of the coarse physical amendment is important and it may be difficult to obtain the desired size range without paying a premium for specially screened material. Also, it is essential to obtain a uniform mixture of the soil and physical amendment. This may be difficult if on-site rather than off-site mixing is used.
Modified soil fields require irrigation facilities and increased attention to the maintenance fertilizer program. Like natural soil fields the crowning of the field restricts multiple use and fields may still become quite muddy under adverse weather conditions. The cost of modified fields is quite high, especially if the physical amendment must be custom screened. However, this increased cost is compensated, in part, by better playing conditions and easier maintenance.
Although quite expensive initially, soilless fields offer a number of advantages over natural or modified soil fields. If the proper sand size is used these fields will have excellent internal drainage, eliminating the need to crown the field and to have open perimeter catch basins. Soilless fields do require internal drainage tile within the playing area to remove the water that rapidly percolates through the sand.
As with modified soil fields the sand particle size range is extremely important and it may be difficult to obtain the desired size range without custom screening. Irrigation facilities are an absolute necessity because of the low water-holding capacity of the sand. Sand fields require intensive management. Although aeration requirements normally are reduced, an intensive fertilizer program as well as frequent irrigation are required. Establishment from seed is more difficult than with a soil medium due to the drying problem, but seeding is recommended in preference to sodding when commercial sod produced on sand is unavailable. The use of sod grown on mineral soil may negate the infiltration advantage of the sand. There also have been some complaints of reduced footing on sand fields where the turf has thinned badly.
A number of variations are used in constructing sand fields. The Prescription Athletic Field (PAT) system developed at Purdue University is a highly modified system involving the installation of a plastic film barrier between the underlying soil and the sand. This film prevents the vertical movement of water out of the system. Tile drainage lines are trenched into the underlying soil at depths of 4 to 18 inches, depending on the drainage tile size. The plastic barrier must follow the contour of the trenches resulting in a closed system. The sand layer over the plastic barrier varies from 12 to 30 inches thick. Moisture content above the barrier is controlled by pumping water into or out of a grid sytem of 2-inch porous pipe buried in the sand and connected to the 4-, 6-, and 8-inch drainage lines. The system rapidly draws water down through the sand by using vacuum diaphragm type pumps, capable of handling both water and air contained in the system. Operating in reverse, the pumps serve as an irrigation system by pumping water into the system. Some PAT fields incorporate electrical cables near the surface to extend the growing season of the grass.
Example Design and Layout
Athletic fields should be designed to meet standard dimensions established for the game for which they will be used. Local conditions and project specifics should be considered when designing fields.
Complete diagrams of field dimensions and markings may be found in official rule books of the Pennsylvania Interscholastic Athletic Association, the National Collegiate Athletic Association, or the professional leagues. Football dimensions and markings, for example, differ among high schools, colleges, and professional leagues. Contours and drainage provisions are particularly important from the standpoint of play and to provide for fast removal of surplus water. Surface grades and the design of subsurface tile lines for water removal are shown in Figures 1 through 7.
Soil compaction is a major problem on athletic fields constructed from soil or modified soil mixes. Its primary cause is trampling and the use of heavy equipment either in construction or maintenance, especially if the soil is wet. Compaction seals the surface and prevents normal movement of air and water into and through the soil. This not only interferes with normal plant growth but also causes very unsatisfactory playing conditions. Good contouring will aid substantially in reducing compaction. Contouring allows rapid removal of excess surface water, which is primarily responsible for chronically wet soil.
Compaction is less of a problem on soilless fields but provisions must be made for their drainage. The high infiltration and percolation rates of these fields normally require the installation of internal drainage tile.
Turfgrasses require a quarter to a third of an inch of water per day. This is equal to approximately 150 to 200 gallons per 1,000 square feet. A good quality loam soil will hold about 1,200 gallons of available water per 1,000 square feet, to a 6 inch soil depth. Therefore, an adequate irrigation installation for turf on a loam field should be capable of supplying the turf with a minimum of 1½ inches of water every 7 to 9 days. Sand has a much lower water holding capacity than loam soils. Irrigation systems for sand fields should supply the turf with a minimum of 1½ inches of water about every 4 to 5 days. The proper system is one which will distribute enough water uniformly to meet maximum turf needs.
Irrigation systems vary from padded pop-up types of sprinklers, spaced uniformly over the entire playing area, to occasional outlets on the perimeters. Traveling sprinklers, with hose connections to perimeter outlets, provide very satisfactory and efficient irrigation for athletic fields. They apply water uniformly over an area and are readily adjusted to wind direction and velocity. However, lower initial costs of perimeter outlets may prove more expensive in the end, when consideration is given to the additional labor and equipment required over many years.
The capacity of an irrigation system depends upon many variables such as water pressure, volume, pipe sizes, and sprinkler outlets. Since these vary widely under different local conditions, a competent irrigation engineer or other authority should be consulted when field irrigation is to be installed.
The orientation of fields in relation to the sun must be considered in designing an athletic field. Where daylight use is anticipated, fields should be laid out with the main or long axis north and south.
Proper crowning of gridirons constructed from natural soil or modified soil is a necessity that will ensure excellent surface drainage without interfering with play. The design should provide a 10- to 18-inch crown (approximately 1 to 1.9 percent) sloping uniformly from the center of the field to the sidelines, without pockets. The parallel sidelines should be level. Tile systems are placed along the sidelines with open catch basins to remove water more rapidly than it will be absorbed through the soil (Fig. 1 and 2). Except for cases of seepage and high water tables, tiles under the entire playing area of soil fields may be of little value because surface compaction impedes water movement to the tile.
Figure 1. Football gridiron showing end section and tile lines for natural soils and modified soil fields
Figure 2. Cross section of tile line along sidelines for fields constructed of natural and modified soils. Open catch basins are not necessary for soilless fields, but other specifications would be similar.
The design of natural soil or modified soil soccer fields (Fig. 3) should provide grades with a drop of not more than 1 percent from the center crown to the edges. This is much less than the grade permissible on a football gridiron. Since the high center crown on the latter makes side shots in soccer more difficult, it is not advisable to use an area for both football and soccer. A field of minimum width and a 1 percent slope would have an approximate 9-inch crown. A field of maximum width and 1 percent slope would have an approximate 16-inch crown.
Figure 3. Soccer field showing end section and tile lines for natural soil and modified soil fields
Field hockey fields
The drainage crown for natural soil or modified soil field hockey fields should be the same as for soccer. Due to the nature of the game, crowns greater than 1 percent would be a detriment to play.
Figure 4. Field hockey field showing end section and tile lines for natural soil and modified soil fields.
Standard baseball diamonds normally have the pitcher's mound elevated approximately 15 inches above homeplate and the baselines. The fall from the mound should be turtle-backed and not abrupt to the edge of the mound area. The infield area, from the edge of the mound to the basepaths, should have not more than 1 percent grade. Surface water from the infield can be removed by placing tile lines on the outer edge of the skinned area. These lines should be drained away from the playing area in any manner conforming to local conditions. the outfield should be graded to 1 percent slope, from the center in all directions, with the water carried off at the edges by a catch basin tile system if necessary (Fig. 5). Little League fields are laid out in the same manner but on a reduced scale.
Figure 5. Regulation baseball diamond showing design of tile system.
Soilless (sand) fields for all sports
A false water table normally will develop at the interface of the sand layer and the underlying soil. The underlying soil has very low infiltration and percolation rates in comparison to the sand. Therefore an internal tile drainage system if necessary in a sand field.
Two basic tile systems are used. The most common system (Fig. 6) is to install 4-inch tile lines in the subgrade at a depth equal to the tile size, at 20- to 30-foot intervals across the field. These lines are connected to a perimeter line beyond the field sidelines. A second approach is to grade the subsoil so that sloping channels run the length of the field are are approximately 40 to 50 feet apart (Fig. 7). These channels should have a minimum slope of 2 percent. Gravel-encased tile lines are placed in the bottom of the channels. Excess water drainage from the sand then flows down the underlying slope to the tile lines which are connected to perimeter lines at the end of the field. This system will require more sand than the cross tiling system because it is desirable to maintain 14 to 18 inches of sand at the most shallow point. Conversely, this system requires considerably less tile line and no trenching.
Figure 6. Overhead drawing of a cross-field tile system (tile lines approximately 20-30 feet apart) for modified soil and soilless (sand) fields. Soilless fields do not require open catch basins. Modified soil fields must be crowned, soilless fields may be level.
Figure 7. Longitudinal tile system for all types of soilless (sand) fields. Tile line laid on bottom of swale and encased in gravel. Minimum of 14 to 18 inches of sand at most shallow point.
A clear, complete set of specifications covering in detail all materials, soil preparation, and seeding of any athletic field is a necessity. This will provide a definite and uniform basis on which bids can be made, and, if properly drawn, it will prevent misunderstandings as to exactly what, when, and how a job shall be done. Good specifications add the assurance of quality and proven techniques to the mutual benefit of the customer and contractor.
Specifications will vary widely on individual jobs because of differences in soil, climatic conditions, and use requirements of the areas involved. Certain elements, however, should be common to all. These include a preliminary statement of what is to be done, areas involved, materials to be used, and rates and methods of their application.
An outline of specifications that can be adapted for a wide variety of situations follows. Here, the suggested form of the contract appears first. Explanations of the contract design appear iafter. Your own outline of specifications probably would not use this split-page format.
Section I. Scope of contract
These specifications include:
- Finished grading. Install tile drainage, catch basins, and irrigation system; remove trash and stones; grade and contour; furnish and apply topsoil.
- Preparation of seedbed. Furnish and apply lime, fertilizer, and physical conditioning materials; incorporate materials into the soil.
- Seeding. Furnish and apply specified seed of acceptable purity and germination.
- Vegetative planting. Supply stolons, sprigs, plugs, or crowns of specified species and/or varieties. Plant in specified manner.
- Sod. Supply sod of specified species and/or varieties and lay sod in approved manner.
- Repair and reseeding. Provisions for cases of an unsatisfactory stand.
- Maintenance. Mowing, fertilizing, watering, and pest control provisions.
- Payment provisions.
Authors explanation of contract
Explanation. The scope of contract section summarizes all items in the contract for which contractors will be responsible, beginning with finished grading. It permits them to determine quickly any contract provisions which they will be unable to undertake because of lack of equipment, labor, or for other reasons. While such an initial outline is not essential, it has proved to be a great convenience, particularly when detailed specifications cover various areas and involve several pages of provisions, which otherwise would have to be examined in detail to get the necessary information.
The section should list in order all of the major operations that are called for in the body of the contract. The blanket from indicates the major items usually included in this section. The requirements of the particular job will determine which operations should be included in the specifications prepared for it.
Section II. Seasonal and weather limitations
- Fall planting. Not prior to _____ or later than _____.
- Spring planting. Not later than _____.
- Planting at times other than specified may only be done under specific conditions and with the consent of the owner or owner designated representative.
- All operations shall be performed only when the soil is in proper condition to permit satisfactory work, and with expressed consent of the owner or owner designated representative.
Explanation. The desirability of seedings during optimum periods, and seedbed preparation only under favorable soil conditions, make the inclusion of this section necessary. Continuation of work at other than specified times or conditions should proceed only with the consent of the owner, architect, or other owner designated representative.
Section III. Materials
1. Fertilizers. Shall be of standard quality as designated in Section III, 13, a, b; delivered to site in original bags or bulk; protected at all times prior to application against mechanical or weather damage which would prevent proper distribution; applied at rates and in manner designated in Section III, 13, a, b, and Section V, 2, b, c, d.
Explanation. Because of the wide variety of materials on the market, it is necessary to indicate quality and rate of application of each material for individual area. The concentration of all material requirements in one section simplifies determination of total quantities.
Fertilizers. Fertilizers differ in the quantities of nutrients which they contain, in the ratios in which these nutrients are present, and in the kind of material from which each nutrient is derived. It is essential, therefore, that the rate of application, grade, and composition of each fertilizer used be indicated for each area.
Quantities needed are best determined by soil tests, available through Agricultural Extension Service or other agencies. Specifications should include the grade and the kind of material from which the nutrient elements are derived. For example, a complete tabulation of fertilizer for a football gridiron might be set up as in parts a and b of the table in Section III, 13.
2. Lime. Shall be standards commercial product of quality designated in Section III. 13, c of this section, delivered in bags or bulk and applied at the rate specified in the same paragraph and in the manner designated in Section V, 2, b.
Lime. Rates of application are based o lime requirement tests. Ground agricultural limestone is the recommended form. Its value is based on chemical composition (calcium carbonate equivalent) and degree of fineness. Ground agricultural limestone is available as calcium carbonate (calcite) or as a mixture of calcium and magnesium carbonate (dolomite). Standard ground agricultural limestone contains a minimum of 89 percent calcium carbonate equivalent [calcium carbonate plus (magnesium carbonate x 1.19)], 95 percent passing a 20 mesh sieve, 60 percent passing a 60 mesh sieve, and 50 percent passing a 100 mesh sieve.
3. Physical conditioners. Shall be material designated in Section III, 13, d, e; applied at rate specified in same section and paragraph and in manner designated in Section V, 2, b.
Physical conditioners. Conditioning materials commonly used for improving soil are organic matter and sand. The characteristics of organic matter that have the greatest effect on their value are the kind, organic matter content, and moisture absorptive capacity.
Peats are the most commonly used source of organic matter. They should contain a minimum of 90 percent organic matter and have a minimum water holding capacity of 500 percent. Peats are classified as reed-sedge, sphagnum, and sedimentary. Only the first two should be considered for use as soil conditioners. Sedimentary peats usually contain high percentages of mineral and colloidal matter which cause them to compact and harden under use. Other sources of organic matter such as rotted sawdust, manures, peat humus, spent mushroom manure, seed hulls, licorice root, and sewage sludge are sometimes used, but they generally are not as effective as good quality peat.
Sands vary widely in the size of individual particles and the percentages of each size class present. Graded, washed sands with the fines removed or coarse grades of ground rock are the most satisfactory. Specifications should define clearly the type, particle size, and particle size range.
4. Seed. Shall be commercial grades of types specified in Section III, 13, f, and shall meet requirements of (state-federal) seed laws.
a. Seed shall be delivered at site in original containers and shall not be mixed and blended except in presence of owners or their authorized representative.
b. Seed shall have been tested for germination and purity by accepted methods with a period of _____ prior to delivery. Seed tag shall show date of germination test, germination, and purity indicated in Section III, 13, f.
Seed. In tabulating seed requirements, areas that are to receive different kinds or quantities should be listed separately. If a single species or variety is to be used, it should be designated by its accepted commercial name, such as common Kentucky bluegrass or (varietal name) Kentucky bluegrass.
If mixtures are specified, the tabulation should show ingredients with the percentage by weight of each. Separate purity and germination minimums should be specified for each kind of seed in the mixture.
5. Mulch. Shall be delivered as specified in Section III, 13, g.
Mulch. Mulches are desirable to protect new seedings from washing by heavy rains and to prevent excessive dryiing of the seedbed which may delay or seriously injure germination. Many kinds of materials can be used, hay and straw being the most common. Other materials include asphalt, latex, plastics, wood fibers, paper, and cloth.
The most important items in mulching specifications are the kind, quality, and rate of application of the material used. If local supplies of an acceptable material are available, the specifications should be adapted to provide specific directions for its use.
6. Vegetative material (stolons, sprigs, plugs, crowns). Shall be of quality, species, and/or varieties designated in Section III, 13, h; vegetative material to be planted at rates specified in the same paragraph by methods specified in Section V, 4, a, b, c.
Vegetative material. Where areas are to be planted vegetatively, the materials tabulation should specify the species or variety of stolons, sprigs, plugs or crowns; their quality, and the rate of planting. One-year-old material usually is the most vigorous and will produce the best and quickest cover. Since stolons or sprigs generally are sold on a volume basis (by bushel or square feet) it is desirable that they be free from soil which would reduce the amount of viable material in a measured unit. Where plugs, sprigs, or crowns are used, the rate of setting also should be indicated, e.g., "on 12-inch centers."
7. Sod. Shall be of species and/or varieties and quality specified in Section III, 13, i; laid in manner designated in Section V, 5, a, b, c, d.
Sod. In specifying sod the important items are the species and variety or mixture, the quality, the size and thichness of sod pieces, and the type of soil (mineral or organic) the sod is grown on.
8. Drainage blanket. Shall be material designated in Section III, 13, j; applied at rate specified in same paragraph, and in manner designated in Section V, 1, a.
Drainage blanket. Material used for the drainage blanket should be specified as to type (crushed limestone, washed gravel, cinders, etc.) and size. The preferred material is 1B or 2B crushed limestone as specified by the Pennsylvania Department of Transportation. Washed gravel of 1- to 2-inch diameter is satisfactory.
9. Tile. Shall be of the type and size designated in Section III, 13, k; laid in accordance with the architect's or engineer's plans.
Tile. Type of drainage tile should be specified. Common clay farm tile, plastic, iron, or composition tile may be used. Slit or corrugated tile is very effective, readily available, and by far the easiest to install. If catch basins are supplied in sufficient quantities, solid iron, plastic, or composition pipe may be used. Drawings of the tile system and method of constructing catch basins should be included.
10. Irrigation. All pipe, fittings, sprinkler heads, etc. shall be of type and size specified in Section III, 13, l; installed according to the architect's or engineer's plan.
Irrigation. Type of pipe (plastic, cement, galvanized iron, cast iron, or composition) and size (diameter) must be specified. Drawings of the irrigation system, including method of constructing risers, etc., should accompany the specifications.
11. Topsoil. Shall be of the quality specified in Section III, 13, m.
Topsoil. Where additional fill is required to bring an area to grade specifications or where the existing soil is of very poor quality, it may be necessary to use topsoil. In such cases, the specific areas to be covered should be defined and the required depth of fill specified. Also, a definite statement should be made under the quality column indicating the character and quality of the soil used. Quality of topsoil is difficult to characterize. Soil tests provide information on soil reaction, basic nutrient availability, and organic matter content. Textural classification, according to the United States Department of Agriculture classification system, should be indicated. Aggregate structure and freedom from noxious weeds such as quackgrass, bentgrass, and common field weeds can be determined by an experienced agronomist prior to purchase or use. Topsoil should be natural surface soil from well-drained areas. It is desirable to have a sandy loam soil containing less than 30 percent silt and less than 10 percent clay.
12. Pesticides. Shall be type specified in Section III, 13, n.; applied at rates specified in same paragraph.
Pesticides. It is sometimes desirable to use special materials in preparing a seedbed for growing turf. These include such things as sterilants, insecticides, and other pesticides. Where these are used, the materials tabulation should list each one separately with definite statements of the required quality plus rate and method of application. The stage of construction when applying these materials should be indicated.
13. Quality and rate of application. All materials shall be of quality and shall be applies on areas at rates shown in the following tabulations under Section III, 13.
Quality and rate of application. Items under the materials section of the specification form are self-explanatory. Adherence to accepted standards provides assurances of having satisfactory materials on the job in their proper condition. Where different areas are involved, provision is made in the tabulation for specifying the quality and quantity of individual materials needed for each. This requires a seperate description (identificaiton and size) of the areas under each material specified.
Tabulations of material qualities and rates of application (Section III, 13)
Note: Examples are for illustrative purposes only and should not be construed as recommended fertilizer programs for athletic fields.
a. Basic fertilizer SAMPLE
Materials and Methods of Construction
Building a good athletic field requires more than a clear set of specifications. The kind and quantity of materials to be used, how and when they are applied, and the manner in which the work is done are just as important. A number of things must be adjusted to the specific conditions of the individual job. The basic principles affecting the use of fertilizers, lime, and other materials, and the relationship of the kind and condition of the soil to methods of its preparation are vital factors in producing good turf at the lowest possible cost.
Soils and sands vary widely in the quantities of available plant nutrient materials which they contain. Nutrients most likely to be deficient are nitrogen, phosphate, and potash. Soil tests, available through the Agricultural Extension Service and private concerns, will provide adequate information on the need for phosphate and potash. When tests show medium to low levels of these materials, liberal applications should be made in preparing the seedbed for turf. Adequate quantities of phosphate and postash can be supplied by applications of 50 to 60 pounds per 1,000 square feet of 0-25-25 fertilizer or equivalent. The material should be applied prior to tillage operations and worked into the soil as deeply as possible.
Soil tests are not a reliable measure for determining the quantity of nitrogen that should be used. They show only the quantity of soluable nitrate nitrogen present. This type of nitrogen is utilized or lost very rapidly. The Pennsylvania State University soil testing laboratory does not test for nitrogen in samples submitted for turfgrass establishment.
Three basic facts control the use of nitrogen for turfgrass establishment. These are the needs of the grass itself, the kind of nitrogen applied, and the depth to which it is mixed into the soil. It seldom is necessary to apply more than 1 pound of quickly available nitrogen per 1,000 square feet to meet the normal requirements of the young seedling grass. If larger quantities are applied, total losses from leaching may be greater and there is danger of overstimulation that may make the young grass more susceptible to damping-off and other diseases. This immediately available nitrogen may be exhausted quickly, requiring reapplication within 3 to 4 weeks. The necessity for a second application in such a short time may be avoided by supplementing the intial application with an 3 to 4 pounds of nitrogen per 1,000 square feet derived from materials such as natural organics, ureaform compounds, IBDU (isobutylidene diurea), or sulfur-coated urea, which release nitrogen slowly. Thus there is less danger that the nitrogen will be lost through leaching and denitrification before it can be used by the grass roots.
It is best to apply fertilizers containing nitrogen just prior to seeding. These also should carry phosphate and potash, even though previous applications of these nutrients have been made. This will insure that liberal quantities of the nutrient materials will be available to developing seedlings. The starter fertilizer shoud be worked into the soil to a depth of not more than one inch. If a material containing nitrogen in soluable form is used, the nutrient ratio should be 1-1-1: one part nitrogen to one part of phosphate to one part of potash. A grade such as 10-10-10 would conform to this. The fertilizer should be applied at a rate that supplies 1 pound each nutrient per 1,000 square feet. If a fertilizer containing 35 percent or more of the total nitrogen as water insoluable nitrogen or controlled release nitrogen is used, the ration of nitrogen to the other nutrients can be increased to 2-1-1 or 3-1-1 and the material applied at a rate to supply 3 to 4 pounds of nitrogen per 1,000 square feet.
It sometimes is necessary to supply other essential nutrients, depending upon local soil conditions. Sandy soils are more likely to be deficient than silt or clay soils. Agricultural experiment stations in most states have made detailed studies of the need for trace elements. Ask your Agricultural Extension Service for its recommendations.
The soil reaction (degree of acidity or alkalinity) affects the activity of soil microorganisms, the availability of plant nutrients, the growth of grasses, and the activity of disease-causing fungi. Soil microbial activity is essential to the decomposition of clippings and other organic matter and to the breakdown of certain types of fertilizer materials and their subsequent conversion to nutrient forms that can be utilized by the plants. At pH values of 7.5 or under 5.5 certain plant nutrients become limiting through the formation of insoluable compounds. Most grasses make their growth in a pH range of 6.0 to 7.5. Fungi which cause 99 percent of our turf diseases are favored by high acidity. It is fortunate that grasses make their optimum growth, nutrients are most available, soil microorganism activity greatest, and fungi activity is reduced at a pH range of 6.0 to 7.5.
Lime is the most economical and most readily obtainable material for correcting soil acidity. Soil testing laboratories have equipment to make lime requirement tests. Properly take soil samples representative of the area should be submitted to them and lime applications based on the results of the test. Lime requirement test recommendations are based on standard ground limestone. Application rates should be enough to meet the full lime requirement. Lime should be applied prior to preliminary tillage operations and worked into the soil to a minimum of 5 to 6 inches.
Physical conditioning material
Soil compaction is one of the most common causes of poor turf on athletic fields constructed from natural or modified soil mixes. It is caused by squeezing together of the soil particles during trampling and by the use of heavy construction or maintenance equipment. Heavy soils with high proportions of fine silt and clay compact more than lighter sandy types containing large quantities of coarse particles.
Compaction reduces the rate of movement of air and water through the soil. This results in stagnant conditions that prevent grass roots from functioning normally. They first become shallow and eventually die. As a result the turf weakens, loses its vigor and density, and is more subject to injury.
The effects of compaction can be minimized by adding conditioning materials when the field is built. Materials most commonly used for this purpose are sand and some form of organic matter. The quantity and quality of sand used will depend upon the character of the soil to be treated. Heavy clays and silts may require as much as 50 to 60 percent sand by volume, mixed to a five inch depth, to improve their resistance to compaction while retaining the firmness necessary for good playing conditions. Soils with higher contents of natural sand do not require as much addtional sand for conditioning.
Sand for soil modification
The effectiveness of sand for soil modification is dependent on particle size, particle size range, and the amount of sand used. Graded sands with the fines removed are best adapted for use as physical conditioners. The specifications should designate the type (i.e., washed ground silica rock) and the percent of each particle size in the range previously designated. Research at The Pennsylvania State University indicates that a uniform coarse sand (80 percent between 1.0 and 0.50 mm and 95 percent between 2.0 and 0.5 mm) to be more effective than finer and less uniform mortar and concrete sands. It is suggested that at least 80 percent of the sand be between 2.0 and 0.5 or between 1.0 and 0.25 mm. Narrower size ranges would be desirable, but locating a nearby source and the high cost of such material are limitations to specifying narrow ranges of sand size. Some of the finer and non-uniform sands that are available may be acceptable as amendments, but considerably larger quantities are required to obtain desirable results. Non-uniform sized sand contains many different sizes of particles, and the beneficial effect of particle bridging may be lost as smaller particles fill the voids created by larger particles.
Sands for soilless construction
Sands used for soilless construction should be finer textured than sands used for soil modification. Sands having approximately 60 percent in the medium size range (0.5 mm to 0.25 mm) and 95 percent in the very coarse to fine sand range (2.0 mm to 0.125 mm) currently are recommended. The reasoning is that if the coarse fractions equal or predominate the medium fraction, the sand tends to be droughty and unstable. A sand high in very fine and fine fractions has slower drainage characteristics and may restrict water infiltration. If the sand has equal distribution of coarse, medium, and fine particles the result is a harder surface with reduced drainage potential. Thus, the key fraction must be medium sized sand to insure reasonable water holding capacity and firmness. The sand size recommended by Purdue University for PAT fields is approximately 0.125 mm to 0.5 mm (fine to medium sand).
Various types of organic materials also are effective in reducing soil compaction. Raw or cultivated reed sedge peats are well adapted for this purpose. They have a high moisture-absorptive capacity, and improve aeration of the soil. Where peats are used, it is seldom necessary to apply them at rates of over 10 percent by volume. Depending upon the depth to which they are mixed, this would require 1 to 3 cubic yards of peat per 1,000 square feet of area. Organic matter may be mixed into the top 2 to 3 inches of sand fields to improve the moisture holding capacity, especially during the establishment period.
Other types of organic materials may be used to make soils more resistant to compaction. These include such things as sewage sludge, tannery wastes, seed hulls, and well-rotted sawdust. Most of these materials, because of their faster rates of decomposition, are effective for a much shorter time than peats. The quantity applied must be estimated on the basis of moisture content, physical character, and relative persistance in the soil. Sewage sludge may contain 30 percent or more water, so that relatively high rates of application will be necessary to obtain the required quantity of dry matter. Seed hulls usually are light and fluffy and are difficult to mix uniformly into soil when applied at heavy rates. Rotted sawdust decomposes relatively slowly and can be used at volumes approximating the rate of application for peats.
The maximum value of any soil-conditioning material is obtained only when it is uniformly mixed into the soil to the specified depth. Various tools, such as rotary hoes, rotovators, or disks, can be used. The operation should be checked repeatedly to assure that a thorough job is done. When both peat and sand are to be used, the peat should be spread first with the sand following. The heavy sand will help to work the lighter peat throughout the mixture.
Seed preparation is a critical operation in constructing an athletic area. Improper seedbed preparation or preparation under adverse weather or soil moisture conditions may result in complete seeding failure. Working soils containing excessive moisture, especially with heavy equipment, will destroy the physical condition of the soil. Destruction of the soil physical condition increases soil compaction with a resultant reduction in aeration and drainage of the soil. Compaction impedes the movement of fertilizer nutrients, water, and air into the soil. The basic premise in modifying soils with sand and/or organic matter is to reduce the compactability of the soil.
In addition, the physical condition of the soil can be destroyed by overtillage. This is especially true if a rapidly revolving tine type rotary tiller is used. This machine tends to beat the soil to the degree that soil structure is destroyed. Rotovators, on the other hand, are quite satisfactory for seedbed preparation. Rotovators, in contrast to rotary tillers, are equipped with shovel-like cultivators which revolve relatively slowly. Plowing provides an acceptable method of tillage provided care is taken to work out, by disking and floating, the uneveness caused by the furrows. Depending on the soil involved, tillage by disking alone may be satisfactory.
The final seedbed should be a homogeneous mixture of the original soil, physical amendments (sand and organic matter), lime, and fertilizer. When mixing sand and organic matter into the soil, the organic matter should be laid down first with the sand on top. Tillage tends to float the light organic materials upwards while the heavy sand moves downward. Layers of any given material must be avoided. Disruption of the soil continuity may cause serious drainage problems. Tillage depth should be a minimum of 6 inches. If no drainage blanket is used under the topsoil, tillage should be sufficiently deep to mix a minimum of 3 inches of the subsoil with the topsoil. This will provide a transition zone between the subsoil and the topsoil without a sharp line of demarcation between the two.
Prior to application of the starter fertilizer, the seedbed should be firmed to indicate the presence of pockets or soft spots in the seedbed. Such areas must be eliminated by regrading. The starter fertilizer may be worked into the top 1 inch of soil with a York rake or similar tool.
Grasses and seed mixtures
The species and variety of grass and the quality of the seed are important items in constructing an athletic field. Turf should be composed of those species tha are most wear resistant and at the same time capable of quickly healing injuries caused by play. Good seed of high purity and germination is necessary to produce a dense, vigorous turf that can be used in the shortest possible time.
In the northern section of Pennsylvania and at elevations above 1,000 to 1,200 feet in southern sections of the Commonwealth, recommended seedings are Kentucky bluegrass blends with or without improved turf type ryegrasses; tall fescues alone; and mixtures of Kentucky bluegrass and fine fescue with or without improved turf type ryegrasses. In the southern sections of Pennsylvania (with less than 1,000-foot elevation), best results are obtained from Kentucky bluegrass blends with or without improved turf type ryegrasses and from tall fescue alone. The use of fine fescue for athletic fields should be avoided in southern Pennsylvania. The use of tall fescue is questionable throughout Pennsylvania unless you do not use the athletic field for two growing seasons, to allow the grass to develop a well-established root system. Tall fescue should not be used for baseball infields or field hockey fields; the coarseness and potential clumping of this bunch type grass may deflect the roll of the ball.
Kentucky bluegrass varieties vary greatly in their genetic base and consequently show considerable variation in resistance and/or susceptibility to various turfgrass diseases, growth habit, vigor, density, color, mowing height tolerance, and nutrient requirements. For these reasons blends of Kentucky bluegrass varieties are preferred over the use of a single variety. When seed specifications call for Kentucky bluegrass blends, a minimum of three and maximum of five varieties should be used with no single variety being less than 20 percent of the blend.
Seedings of Kentucky bluegrass blends or Kentucky bluegrass and fine fescue mixtures may be supplemented with 10 to 15 percent improved turf type ryegrass is desired. In certain unusual situations as much as 50 percent turf type ryegrass may be suggested. When seedings are made at other than optimum times such as early to mid-summer and late fall, it is desirable to include 15 to 20 percent improved ryegrass in the mixture. These ryegrasses are quite compatible with Kentucky bluegrass and have better mowability and persistance than the older common types.
For the latest varietal recommendations for Kentucky bluegrass, fine fescue, and turf type ryegrass, obtain Special Circular 168 Turfgrass Seed Mixtures from your county Extension office.
Recommended grasses and seeding rates
|Formula||Percentage of mixture||Rate of seeding|
|For athletic areas in southeastern Pennsylvania, south and east of south mountains|
|1. Kentucky bluegrass blend* (3 to 5 varieties)||100||3 lb per 1,000 sq ft|
|2. Tall fescue||100||10 lb per 1,000 sq ft|
|For other Pennsylvania areas|
|1. Kentucky bluegrass blend* (3 to 5 varieties)||100||3 lb per 1,000 sq ft|
2. Kentucky bluegrass* (2 or 3 varieties)
|4 lb per 1,000 sq ft|
|3. Tall fescue||100||10 lb per 1,000 sq ft|
|For slopes, banks, cuts, fills in all Pennsylvania areas|
|1. Penngift crown vetch|
Tall fescue or fine fescue or perennial ryegrass
|3 lb per 1,000 sq ft|
|2. Tall fescue||100||6 lb per 1,000 sq ft|
|1. Tall fescue||100||8 lb per 1,000 sq ft|
*10 to 15 percent turf type ryegrass may be added to these mixtures.
The quality of seed depends upon its purity and viability. Purity refers to that percentage of a pound which is seed of the species, variety, or mixture named. Thus, a pound of Kentucky bluegrass seed that shows 90 percent purity would contain nine-tenths of a pound of seed of that species. The remaining one-tenth pound would consist of inert matter, such as stems and chaff, and seeds of other grasses or weeds.
The viability of seed refers to that percentage of pure seed in a pound that will germinate when subjected to a standard laboratory germination test. If a pound of commercial seed is 90 percent pure shows 80 percent germination, only 72 percent (80 percent of 90 percent), or less than three-quarters of the pound is viable seed. Since purity and germination percentages may vary widely for different grasses and with individual lots of seed, rates of seeding must be adjusted to the actual figures for any lot. The rates specified in the prior table are based on the following purity and germination percentages for the various grasses.
|Species or variety||Minimum purity, %||Minimum germination, %|
|Kentucky bluegrass, named variety||95||75|
|Kentucky bluegrass, common||85||75|
|Perennial ryegrass, improved turf type||98||90|
|Penngift crown vetch||98||75*|
*Including hard seed not to exceed 35 percent.
Methods of seeding
The most important items in seeding turfgrass areas are uniform distribution, proper cover, and firm soil around the seed. Various types of mechanical seeders will distribute seed uniformly when they are correctly calibrated and operated. These can be divided into two general classes: (1) the hopper and cyclone types which drop the seed on the surface of the seedbed, and (2) the cultipacker type which distributes and covers the seed, and firms the soil in one operation. If the hopper or cyclone type is used, seed must be covered by light raking, harrowing, or dragging, and these operations must be followed by light rolling to firm the soil. In either case, the seeder should be calibrated to determine the proper setting for the kind of seed and desired seeding rate.
Calibrating can be done in various ways. A simple method is to hang a shallow pan under the seed hopper and operate the equipment at a standard speed for a given distance at a trial setting. The distance traveled multiplied by the width of the hopper will give the area covered. Seed discharged into the pan can be weighed to show the quantity used on the area covered. Settings then can be adjusted to deliver more or less as desired. Cyclone seeders normally are calibrated by a trial and error method. If a known amount of seed is placed in the hopper and completely run out, the amount of seed applied to a specific area can be calculated. By adjusting the hopper opening and repeating this process, reasonably accurate calibration can be optained.
To secure maximum uniformity in distribution, it is desirable to set the machine to deliver half of the total rate desired. This will permit making two passes over the area. Best results are obtained when the second pass is made at a right angle to the first.
Hydroseeding is also an acceptable method of seeding athletic fields. Lime, fertilizer, and mulch should not be mixed with the seed in the hydroseeder. Frequently, with this combination, the seed does not have firm contact with the soil. Lime and fertilizer should be worked into the seedbed in the conventional manner prior to hydroseeding. Hydromulch should be applied in a separate operation following hydroseeding.
Dormant seeding may be used to advantage when construction schedules prevent seeding at optimum times. The object is to gain several weeks' growing conditions in early spring. The principle of dormant seeding is to sow seed during winter when weather conditions normally prevent germination and seedling establishment of all species. It should be emphasized that dormant seedings seldom are as successful as conventional seedings. Unusually warm spells during the winter may initiate germination, with seed and/or seedling loss during subsequent freezing weather.
Mulches are used primarily to protect against washing prior to germination and establishment of the new turf, and to prevent rapid drying out of the seedbed which might delay or injure germination. They are effective, also, in protecting late fall seedings from winter injury.
Hydromulching, using various wood fiber products, is an excellent and rapid method of mulching. The wood fiber and water slurry tend to bind the mulch to the soil and eliminate the need for "tie-down" materials often necessary with other mulching materials. Mulching rates with these products vary from 1,000 to 1,500 pounds per acre.
Other materials commonly used are straw of cereal grains such as wheat or oats, or some form of hay or coarse grass clippings. Mulching rates with these materials vary from 1½ to 2 tons per acre, depending upon how uniformly they are spread. Machines have been developed that spread mulch mechanically. These do an excellent job and should be used if available. However, hand spreading is not difficult and can be done rapidly.
Various methods can be used to hold the mulch in place. It can be weighed down by placing boards or brush at intervals over the area. These can be removed as soon as the mulch has been thoroughly wetted down and flattened into place, and before the seed has germinated. A system of stakes and tie-down strings also is effective. For best results, the stakes should be placed on 40-foot centers and the strings stretched between them in a systematic design.
Where equipment is available, the mulch cover can be sprayed with a solution of cut-back asphalt at a rate of one-tenth gallon per square yard. The asphalt serves as a binding material that holds the mulch in place. This method requires special spraying equipment. It is expensive and there is little evidence that it is effective enough to justify the additional cost and trouble involved. Also, several latex based sprayable mulches do an acceptable job.
If the mulch has not been spread uniformly and is so heavy on certain areas that the young seedlings have difficulty growing through it, part of it should be removed. Where the grass shows green above the mulch it can be left on without danger of injury to the turf.
Sodding is the quickest but most expensive method of initially establishing turf. Its use on an athletic field is best suited to those situations requiring a mature, wear resistant turf cover in a short time. A properly laid sod on a well-prepared sodbed will knit and be ready for use within 4 to 6 weeks. In contrast, one full growing season is needed to produce comparable turf by seeding.
Sodding generally is not recommended for sand field construction unless sod grown on a comparable sand can be found. Sod produced on heavy soil may impede water infiltration into the sand. Sod produced with commercial sod netting should be avoided on all fields. Player cleats penetrating the sod may become entangled in the netting, causing the player to fall or to rip out large pieces of sod.
A successful sodding operation depends on the quality of sod, its condition, and the care used in preparing the bed and laying the sod. Unless quality sod is used, results will not justify the high cost involved in establishing turf by this method. It should be dense and well knit so that sod can be cut as thin as possible, and in long strips that can be rolled to facilitate handling. Thinly cut sod weighs less, lies better, and roots quickly. Quality sod of the grasses adapted for use on athletic fields should have a maximum root and soil thickness of one-half to three-quarters of an inch. It should be cut in strips 12 to 18 inches wide and 4 to 6 feet long. This makes a convenient size roll for handling. If cut sod is to be held for several days before laying, it should be spread out flat, grass side up, in a cool place and kept moist. Rolled or stacked sod will weaken and yellow rapidly and will not be in good conditiion to start growth promptly when laid.
Preparation of the sodbed, including liming, fertilizing, and soil conditioning, should be the same as for seedbeds. The surface should be firmed by rolling, and, if dry, it should be wet down with a fine spray just prior to laying sod.
The first course of sod should be laid to a line that has been squared to the longitudinal axis of the field. Sods of the next course are matched against the first so that the joints between pieces inn the adjacent courses do not coincide. The sod is tamped lightly as it is set to insure good contact with the soil surface at all points. Any openings that occur in the seams between pieces should be filled with prepared topdressing to prevent excessive drying out at these spots. In periods of dry weather, a regular watering program should be followed until the sod has rooted.
Freshly laid sod should not be rolled. Rolling at this time often causes the sod to creep ahead of the roller and usually does more harm than good. After rooting has occurred, a light roller can be used to smooth out minor irregularities.
Establishment of turf by vegetative planting is limited to those grasses that spread by creeping stems or runners. The process consists fo shredding sod grown in nurseries for this purpose and planting the material on a prepared seedbed. The shredded sod can be broadcast over the entire area or planted in spaced rows. If broadcast, it must be covered to a depth of a quarter of an inch to half an inch with prepared topdressing soil. If planted in rows (sprigging), the runners are set in open furrows 2 to 3 inches deep and covered by backfilling soil over them. In either case, seedbed preparation should be the same as for seeding, and the entire area firmed by light rolling after planting.
From 5 to 10 bushels of shredded planting stock will be required per 1,000 square feet of area to be planted if the broadcast method is used. When planted in rows, one bushel of planting stock will plant about 600 linear feet of row. Rows can be spaced from 12 inches (or less) to 2 feet, depending on the kind of grass and how quickly complete cover is required. Zoysia rows require closer spacing than Bermudagrass because of zoysia's slower growth rate.
Plugging involves the planting of blocks or plugs of sod at measured intervals throughout the area. Size and spacing of plugs must be determined by the amount of planting material available and the desired rate of spread. Plugs should fit tightly into the prepared hole and then be firmly tamped into place.
The only grasses adapted to Pennsylvania conditions, and which are practical to plant vegetatively, are Bermudagrass, zoysia, and creeping bentgrass. Since Bermudagrass and zoysia are climatically adapted only to the extreme southeastern part of Pennsylvania and creeping bentgrass does not make a satisfactory athletic field turf, vegetative planting has only a very limited application.
A good maintenance program is just as necessary to ensure athletic field turf of satisfactory quality as are sound establishment methods.
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 for 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:
Fertilizer Program 1. For natural soil and modified soil fields where soil tests show minimal* to adequate levels of phosphorus and potassium, or no soil test has been made.
|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||60-30-30||100-50-50|
|25% to 49% of the N derived from a slowly available source||60-30-30||50-25-25||50-25-25|
|water soluble N||40-20-20||30-15-15||50-25-25||40-20-20|
Fertilizer Program 2. For natural soil and modified soil fields where soil tests show very high levels of phosphorus and potassium.
|Nitrogen source||Time of Application|
|Late spring||Early summer||Late summer||Early fall|
|Pounds per acre applied|
|Natural organic (5-7% N)||900||765||1,000|
|Ureaform (38% N)||230||200|
|IBDU (31% N)||250||275|
|Sulphur coated urea (SCU) (approx. 32-37% N)||250||250|
|Urea (45% N)||90||90||100||90|
Fertilizer Program 3. For soilless (all sand) fields.
|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||80-40-40||68-34-34||68-34-34|
|* 25-49% of the N derived from IBDU, SCU, or methylene urea||44-22-22||44-22-22||64-32-32||64-32-32|
|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.
Maintenance Guidelines Schedule
The following outline is offered only as a guide. Depending on weather fluctuations, location within the state, and localized conditions, this schedule may vary as much as plus or minus 2 to 4 weeks, especially as regards timing of operations and applications of materials. This outline is suggested for use on general athletic fields and fields that primarily receive late summer and fall use. Fields receiving spring and early summer use only, such as baseball fields, may require slightly different sequence of operations. The maintenance schedule will vary with the type of field construction. Sand fields, for example, will require a more intensive fertilization and irrigation program than will soil fields. Soil fields normally require a more intensive aeration program than will sand fields.
Late February to late March
Seeding on honeycomb (where feasible). Apply seed in early morning when soil is frozen and is expected to thaw during the day. Divide total amount of seed to be sown into three to four equal lots and apply on three to four different mornings. Use a certified variety of turf type perennial ryegrass or a blend of certified turf type perennial ryegrasses. Seeding rate may vary from 1 to 5 pounds per 1,000 square feet depending on existing turf density.
Soil test. Soil test mailing kits are available from your county Extension Service office. Be sure the sample submitted is representative of the entire area.
April to early May
Clean up.Collect any debris that has collected over the winter months such as leaves, paper, and other trash.
Aerate six to ten times over with a spoon type or hollow tine type aerator that removes soil cores. Do not use spiker type equipment.
Overseed or reseed. Overseed (where some turf exists) immediately following aeration. When it is available, use a disk type turfgrass seeder to cut the seed into the soil. If a disk seeder is not available, broadcast seed evenly over the area. Immediately follow either seeding method with some form of covering operation. Use a drag mat, flexible tine harrow, or weighted piece of chain link fence. Use same seed and rate as recommeneded for seeding on the honeycomb.
Reseed where no turf exists. Lightly disk the area to provide a seedbed. Then broadcast seed, rake, or drag lightly to cover seed, and roll lightly to put seed in firm contact with the soil. Use same seed as above at full 5 pounds per 1,000 square foot rate.
Mow as needed. Cut at height of 2 to 3 inches. Never remove more than one-third of the total leaf surface at a given mowing. Keep mowing equipment sharp and properly adjusted.
Mid April to early May
Crabgrass control, preemergence. Application date for preemergence crabgrass control materials varies greatly with weather conditions. Apply material when soil temperature in the surface inch reaches 60°F (16°C). If area has been overseeded or reseeded, siduron (Tupersan) is the only preemergence material that may be used. When siduron is used a second application at approximately one-half rate must be made 4 to 6 weeks after the initial application. If area has not been seeded DCPA (Dacthal), bensulide (Betasan), or benefin (Balan) may be useful for the preemergence crabgrass control.
Mow as needed.
Early to late May
Fertilize. Fertilization should be withheld until leafspot conditions (cool, wet weather) subside and should be based on soil test results. In lieu of a soil test, follow guideline fertilizer programs. Use a turf type fertilizer containing 30 percent or more water-insoluable nitrogen (WIN), derived from ureaform, IBDU, or a natural organic; or controlled release nitrogen (CRN), derived from sulfur coated urea.
Mow as needed.
Chickweed and/or knotweed control. Apply 2,4-D plus mecoprop (MCPP) or 2,4-D plus dicamba (Banvel). Do not use if area has been seeded.
Disease control. High quality fields containing high Kentucky bluegrass populations may require fungicide applications for leafspot control. Two to four applications at 10- to 14-day intervals may be required. Recommended fungicides include anilazine (Dyrene), chlorothalonil (Daconil 2787 WP or F), cycloheximide (Actidione), iprodione (Chipco 26019), and maneb fungicides (Maneb WP, Tersan LSR, Fore).
Insect control. If a heavy white grub (Japanese beetle, Northern Masked Chafer, May-June beetle) population has been carried over from the previous fall it may be necessary to apply an insecticide at this time. Recommended insecticides include isofenphos (Oftanol), diazanon (Diazanon), chlorpyrifos (Dursban), and trichlorfon (Dylox, Proxol).
Mow as needed.
Fertilize. The use of fertilizers containing soluable nitrogen or less than 30 percent WIN or CRN will necessitate more frequent applications. Sand fields, regardless of nitrogen source, will require more fertilizer applications than soil fields. See the suggested guidelines found earlier in this publication.
Crabgrass control, postemergence.If preemergence control was not applied it may be necessary to apply at postemergence herbicide. Two to five applications may be required depending on the pattern of crabgrass germination. Materials should be applied only when there is adequate soil moisture and air temperatures do not exceed 80°F. Do not apply if area has been spring seeded. Recommended materials include a number of methanearsonates (AMA, DSMA, CMA, MAMA, MSMA).
Knotweed control. Do not apply knotweed control herbicides if area was spring seeded. Control may be obtained until approximately the end of June with mecoprop (MCPP). Beyond this date it will be necessary to use dicamba (Banvel).
Clover control. Mecoprop (MCPP) or dicamb (Banvel) may be used for clover control. Do not apply if area has been spring seeded.
Mow as needed.
Irrigate as needed. Amount of water applied and frequency of irrigation depend upon soil type and natural rainfall. If drought occurs and irrigation is initiated, continue to water throughout the drought period. During drought periods sandy soils wil require approximately 1/3 to ½ inch of water every 2 to 3 days, loam soils will require approximately ¾ inch of water every 5 to 6 days and heavy soils will require approximately 1½ inches of water every 8 to 10 days.
White grub control. Ther most serious white grub infestation normally are the occurence of Japanese beetle grubs from mid-August until the soil begins to freeze in the fall. If isofenphos (Oftanol) is used it should be applied in mid to later July for most effective control. If an application of isofenphos was made in the spring there will be sufficient carryover to control the later summer infestation. If either diazinon (Diazinon), chlorpyrifos (Dursban), or trichlorfon (Dylox, Proxol) is used it should be applied about September 1 to 10.
If the area becomes infested with grubs of the black turfgrass ataenius, the grubs will be most prevalent in June through mid July. Insecticide should be applied as soon as grubs are observed.
Late August to early September
Aerate lightly (one to three passes) and drag to break up cores. Irrigation may be necessary prior to aeration to obtain maximum spoon or tine penetration.
Weed control. Broadleaf weeds can be controlled at this time with 2,4-D. Do not attempt to control crabgrass or knotweed at this time. Clover can be controlled at this time with mecoprop (MCPP).
Mow as needed.
Irrigate as needed. It is suggested the field be kept low in soil moisture for games and irrigated after use.
Mid September to mid October
Aerate and overseed. Some superintendents find it beneficial to lightly aerate (one pass) and lightly overseed (¼ to ½ pound per 1,000 square feet) with turf type perennial ryegrass every week or two during the fall playing season, especially prior to or just following game use.
Mow as needed.
Irrigate as needed.
Thatch build-up is seldom a problem on athletic fields.
Mid November to early December
Aerate six to ten times over, with a spoon type or hollow tine type aerator at the close of the fall playing season.
Basic fertilization. If a soil test indicates additional amounts of phosphate and/or postash are required due to low soil levels apply these materials immediately following aeration.
Lime. If a soil test indicates the need for lime, apply the required amount of ground agricultural limestone just prior to or immediately following aeration.
Dormant seeding. Some superintendents feel that domant seedings at this time are beneficial. The success of dormant seedings is highly dependent on winter weather conditions. Mild, wet spells may cause rotting of the seed. Dormant seedings normally are not highly successful.
The following should be included under the above heading Late August to early September
Fertilize. Apply fertilizer in accordance with soil test results. In lieu of a soil test, follow guideline Fertilizer Program 1 found earlier in this publication.
Prepared by John C. Harper II, professor emeritus of agronomy.