Selection of turfgrass species and improved cultivars is one of the most important decisions a sports field manager can make to ensure a healthy turfgrass stand. Selecting the wrong species can contribute to poor density, poor playability, and alterations in nutrient and water inputs. Sports field managers should select turfgrass species and cultivars based on the existing site conditions, the intended maintenance, expected wear and the intended use of the turfgrass. Criteria include the selection of:
Drought-tolerant species and cultivars where water is limited or not available.
Wear- and compaction-tolerant species and cultivars for heavy play, high traffic areas, and recovery rate.
Disease-tolerant and endophytic cultivars to reduce pest damage and pesticide use.
Shade-tolerant species and cultivars for areas with limited or restricted light.
Turfgrass breeding programs have made tremendous advances in the development of improved turfgrass species and cultivars. Within each turfgrass species, cultivars can now be selected for improved characteristics such as increased lateral growth and tillering that help provide denser playing surfaces, tolerance of a lower height of cut (HOC), increased stress tolerance to drought and wear, speed of recovery, and improved pest resistance, shade tolerance, and salinity tolerance. As a result, managers can select species or cultivars requiring less water and fertilizer inputs.
When considering natural grass options, managers can consult with Extension specialists who can provide guidance on turfgrass selection for sports fields (e.g., wear tolerance and recuperative potential). In addition, the National Turfgrass Evaluation Program (NTEP), the Alliance for Low-Input Sustainable Turf, and the Turfgrass Water Conservation Alliance provide information on high performance cultivars for different regions of the country. The NTEP website provides searchable data from NTEP testing locations in different states. Sports field managers can also learn about new and improved cultivars by attending educational conferences, workshops, and university turfgrass field days.
Warm Season Turfgrasses
Common bermudagrass (Cynodon dactylon) and hybrid bermudagrass (C. dactylon x C. transcaalensis) are typically the preferred warm season grasses for sports field surfaces. Breeding efforts, particularly for hybrid bermudagrass, have yielded improved varieties that are more wear tolerant and have improved cold tolerance. Hybrid bermudagrasses are established by sod or sprigs, whereas common bermudagrass can also be established by seed. While the choices in cultivars of bermudagrasses are limited compared with those available for cool season grasses, there are important differences in establishment method (seed or vegetative), stand density, cold tolerance, growth rate, and pest tolerance that should be considered in the selection of a bermudagrass cultivar best suited for a sports field.
Zoysiagrasses (Zoyia matrella and Z. japonica) and seashore pasplum (Paspalum vaginatum) are warm season grasses that are also used for sports fields. Zoysiagrasses exhibit greater shade tolerance and seashore paspalum has excellent salt tolerance.
Cool Season Turfgrasses
Cool season turfgrasses used in sports fields include Kentucky bluegrass (Poa pratensis), perennial ryegrass (Lolium perenne), and turf-type tall fescue (Schedonorus arundinaceus, formerly Festuca arundinacea). Based on its recuperative potential from rhizome regrowth, Kentucky bluegrass has long been a popular sports turfgrass species. Perennial ryegrass blends well with Kentucky bluegrass in both appearance and management requirements, but its rapid germination and establishment rate makes it an important turfgrass of heavily trafficked cool season fields. New improved turf-type tall fescue cultivars have better tolerance to lower mowing heights and improved tolerance to cold, drought, wear, and disease. Breeding improvements have expanded the acceptability of turf-type tall fescue further north beyond the transition zone. Therefore, once turf-type tall fescue is established, these improvements have expanded the use of turf-type tall fescues on sports fields, and especially lower input, non- irrigated sports fields. While Kentucky bluegrass and perennial ryegrass are cool season grasses best suited for fields that require a lower mowing height, turf-type tall fescue may offer an option for multi-use fields. For sports fields requiring a lower height of cut specific for a desired ball roll or bounce characteristic (e.g., baseball or field hockey), turf-type tall fescue might not be suitable as more frequent inputs and increased maintenance would be required.
Growing acceptable turfgrass on sports fields in the transition zone can be challenging. Cool season turfgrasses are stressed during prolonged hot and humid summers, while bermudagrass has a 4-5 month dormancy period (loss of green color and no active growth) and annual concerns with winterkill potential. More information about turfgrass selection is published in Grass Options for Athletic Fields in the Transition Zone, University of Kentucky. More information on managing bermudagrass in the transition zone can be found in the Virginia Cooperative Extension publication Optimizing Bermudagrass Athletic Field Winter Survival in the Transition Zone.
Another grassing option in the transition zone that has attracted a great deal of interest is a perennial two-grass system of bermudagrass and Kentucky bluegrass (often referred to as “bluemuda”). The goal is to provide an actively growing playing surface (and green color) regardless of the season. Practitioners and researchers alike continue to refine the management protocol and expectations of the end product, but the strategy has been implemented on sports fields all across the transition zone to varying degrees of success.
The turfgrass establishment phase requires greater quantities of water and nutrients compared with routine maintenance of established turfgrasses. To this end, establishment requirements should be considered carefully to minimize environmental risk during construction, as discussed in the Planning, Design, and Construction chapter.
Whether seeding, sodding, or sprigging, proper site preparation aids establishment and can help avoid long-term problems, such as drainage issues and surface smoothness. No amount of water, fertilizers, and pesticides can overcome an unsuitable soil resulting from poor field construction.Trying to overcome soil limitations with excessive water and chemical inputs increases the level of effort and management expense needed to manage the sports field. Additionally, an increased chance of runoff exists that can potentially impact water quality.
Prior to turfgrass establishment, any drainage issues should be corrected through grading and installation of drainage technologies. Site preparation includes removing any debris that could hinder root growth and limit access to water and nutrients. Soil tests should be conducted to address any limitations (e.g., insufficient nutrient levels or pH). Prior to planting, soil pH adjusters and fertilizer materials should be incorporated into the top 4” to 6” of soil, as needed based on soil test results, especially for immobile nutrients. This is also the time to incorporate any organic or inorganic amendments recommended to improve the physical or biological properties of soil.
Little (or no) soil preparation of thinning or degraded natural grass areas often leads to failed turfgrass establishment. Sowing seed or installing sod into/on a sparse turfgrass canopy will ultimately not be successful if the underlying issues have not been corrected. In compacted soils, the newly emerged seedlings may root but may not adequately penetrate the soil such that the new plants persist. For spot seed renovations, it is recommended to core cultivate the soil in multiple directions, seed, and then drag the cores back into the area after seeding to ensure soil to-seed contact.
Seeding Cool Season Turfgrasses
Turf-type tall fescue, Kentucky bluegrass, and perennial ryegrass sports fields take several months to become fully established. Even 100% coverage does not automatically mean that the playing surface is ready for use. New advancements in turfgrass management may alter the timetable for grow-in in some situations. Fields should not be used until they are able to tolerate and recover from consistent wear. Frequent mowing during establishment encourages tillering in turf-type tall fescue and perennial ryegrass and encourages rhizomatous growth in Kentucky bluegrass. The degree of success and the time required for establishment totally depends on environmental conditions, available nutrients, irrigation and rest during the establishment period. A spring renovated field stressed by summer heat or drought may take longer to fully establish than a field seeded in late summer/fall.
In the transition zone, cool season species should be seeded in the late summer and should not be utilized for play until the spring. If summer conditions are moderate, sports fields renovated and seeded in the early spring can be used in the fall. However, a hot and dry summer will stress the young turfgrass seedlings and may damage the turfgrass stand. Therefore, delaying play until the following spring rather than subjecting the field to play while conditions are stressful, might warrant consideration.
Seeding Warm Season Turfgrasses
Warm season fields can be seeded, with the exception of hybrid bermudagrass, though sprigging is more common. Warm season fields can often begin to tolerate traffic within eight to 12 weeks of establishment, if weather conditions are favorable and adequate nutrition and irrigation are available. However, a longer establishment period is recommended to allow a field to mature and better tolerate traffic occurring from play. If not yet mature, 100% turfgrass coverage does not equate to a playing surface ready for use.
The optimal time to install turfgrass sod is during the growing season, which encourages rooting. However, late-season turfgrass sodding can be an option if the preferred timing is not possible. Turfgrass sod that is laid late in the season can require less water to root and establish as temperatures are more favorable for shoot and root growth. Irrigation requirements are lower when sodding late in the season rather than in the height of summer. In the northern regions of the U.S., sod can be installed until the ground freezes as roots will “knit in” as temperatures begin to warm in the spring.
For a sand-based field, sod should be selected that has been grown on a soil with a similar physical structure as the field. Sod that is grown on clay or organic soils and then installed on a sand-based field will often fail because it will not root properly due to the layering effect of the dissimilar soils. An aggressive cultivation program reduces the layering effect, but it is a long- term process and ideally avoided by matching soil types of sod and field. Layering of fine soil over coarse soil reduces water infiltration and percolation rates, leading to a saturated playing surface.
Turfgrass sod, whether on a native soil field or a sand-based field, can be topdressed to fill in the gaps between the sod pieces to aid in establishment and create a smooth uniform playing surface. The sod should be inspected, regularly after installation to reduce evidence of gaps that might appear and should be topdressed with matching soil.
Bermudagrass sprigs (shredded stems) are generally planted from mid-spring through mid- summer. Southern areas may benefit from early to late spring plantings while areas further to the north in the transition zone may need to wait until between late spring and early summer. It is preferable to sprig as early in the bermudagrass season as possible so the stand can be well established to withstand cooler temperatures and traffic in the fall and winter. While it is certainly not the norm, dormant sprigging has been employed successfully in some locations, but there is obvious potential that a late spring freeze can injure poorly rooted, actively growing plants.
Sprigs can be planted in rows or furrows or by broadcasting them uniformly over the entire field surface; typical planting rates range from 400 to 800 bushels (1,000 - 1,200 bushels for zoysiagrass) of sprigs per acre. Higher rates are planted if it is a late planting date, better coverage is desired, or sprigging into existing turfgrass. Planting early in the season (early to late spring for warm climates and late spring to early summer for the transition zone) may require fewer bushels because the bermudagrass has more time to establish and provide optimum coverage. Cultural management during the first growing season is crucial for survival and success of bermudagrass sprigs. Depending on soil temperature, moisture, and management, sprigged fields can be 100% covered in turfgrass within eight weeks after sprigging. However, what might be a great looking playing surface actually has very poor traffic tolerance at this time; sprigged fields that are only eight weeks old are not mature.
Bermudagrass enters some degree of winter dormancy in many areas of the United States with persistent air temperatures less than 50°F and shorter days in the winter. To provide color and an actively growing playing surface as bermudagrass growth slows, many bermudagrass sports fields are overseeded with a cool season grass, typically perennial ryegrass, in early to mid-fall. Potential issues can arise in the spring when the overseeded cool season grass competes with the dormant bermudagrass when it begins to actively grow. A general overview of overseeding in the transition zone is published in The Need to Overseed, Texas A&M Agrilife Extension.
Though winter overseeding is a common practice for warm season sports fields, careful attention is required to encourage growth of cool season grasses without negatively affecting the underlying bermudagrass.
Timing of Overseeding Bermudagrass
The timing of the seeding event, and the selection of the appropriate turfgrass species, are important considerations in the overseeding process. If seeded too early in the fall, the bermudagrass can still outcompete the overseeded cool season species. If seeded too late, the cool season grass might not establish adequately before the cooler temperatures predominate. To increase overseeding success, the overseeding event should be timed with night temperatures that are consistently around 50°F, two to three weeks prior to the first killing frost.
Spring Management of Overseeded Bermudagrass Fields
In the spring, additional early spring fertilizer applications may be necessary to ensure proper growth and development of the overseeded cool season grass. As the temperatures warm and daylight hours increase, cool season turfgrass competes very aggressively with the transitioning and green-up of bermudagrass. This competition can be an issue until air temperatures consistently reach a high of 80°F. Such competition delays total bermudagrass fill-in and, if a heat wave causes the overseeding to quickly die, results in a thin, soil-exposed stand of bermudagrass. Therefore, gradual transitions from bermudagrass to cool season grass in the fall and back to bermudagrass in late spring are necessary to maintain consistent playability.
To transition from cool season grass to bermudagrass in the spring, a number of methods can be used to manipulate populations of the overseeded cool season turfgrass. Applications of plant growth regulators (PGRs) may be beneficial but must be timed appropriately and prior to bermudagrass green up. Transition-assisting herbicides, such as those in the sulfonylurea chemical class, may be needed to adequately eliminate the cool season turfgrass. These herbicides require warm soil temperatures (> 60°F) for best activity and remove ryegrass from a bermudagrass stand in 2-4 weeks.
Overseeding Cool Season Turfgrass Fields
In cool season grass regions and some areas of the transition zone, overseeding consists of adding new seed of cool season turfgrasses to an existing field of cool season turfgrasses. Generally, that means seeding more Kentucky bluegrass or perennial ryegrass, or a mix of the two, into a Kentucky bluegrass field or a field with a mix of cool season grasses. This type of overseeding provides a better playing surface for current season play and increases turfgrass density for future seasons.
The selection of improved cultivars of Kentucky bluegrass, perennial ryegrass, and turf-type tall fescues for overseeding should take into consideration the differences in germination rate. This helps maximize seed germination and complete establishment of all species in the seed mix. A strategy can be to use a mixture of species with the percentage of each changing from early to late fall overseeding. University Extension specialists can assist in devising a regionally appropriate overseeding strategy.
Erosion and Sediment Control
Exposed, bare or thin fields can be prone to the loss of topsoil. Soil carried by wind and water transports contaminants, which may impair water quality of nearby surface waters. For example, erosion can enrich surface waters, where phosphorus and, to a lesser extent, nitrogen can cause eutrophication. When sediments and soils enter water, they can also increase turbidity, blocking sunlight and impacting aquatic plants and animals. Therefore, prior to any field construction or renovation, erosion and sediment control measures should be documented in an erosion and sediment control plan. Erosion and sediment control measures should be installed prior to any soil disturbance. Once established, turfgrass provides excellent erosion and sediment control.
Cultural practices for newly established turfgrass fields include mowing, nutrient management, and irrigation. These practices are described below with respect to establishment and are covered in detail in the Cultural Practices chapters of this document.
Regular mowing promotes new tiller formation and stimulates turfgrass growth and density. The turfgrass should be allowed to initially grow one-third to one- half higher than the desired HOC before mowing. As an important cultural practice, mowing newly established sports fields should follow the one-third rule. Maintaining cutting units (i.e. providing the sharpest and properly balanced mowing blades or consistent reel to bedknife contact) is critical because it supports a healthier turfgrass plant. The soil should be dry and stable enough to support the weight of mowing equipment without rutting.
One-Third Rule: Remove no more than one- third of the leaf tissue with the first and each subsequent mowing event.
Soil tests should be conducted prior to seeding or sodding. Unless soil tests report deficiencies, supplemental micro- and macronutrient, besides nitrogen may not be needed during establishment. In phosphorus-deficient soils, phosphorous (P) should be applied to the soil before seeding or sodding based on soil test recommendations. For example, a rate ranging from 0.5 to 1.5 pounds (lbs) P2O5 per 1,000 square feet (ft2) (22 to 65 lbs P2O5 per acre) may be recommended. A follow-up application of phosphorus fertilizer may be required four to eight weeks after seedling germination or sodding. If a soil test indicates a deficiency in phosphorus or if symptoms of phosphorus appear (such as purple-blue color, thin canopy, poor nitrogen response) a second application may be justified. Soils with a pH greater than 7.5 are at greater risk of phosphorus deficiency during establishment. Therefore, higher rates and a second application of phosphorus fertilizer are recommended for high pH soils, unless otherwise not allowed by state or local nutrient management regulations.
Nitrogen (N) management is also essential during establishment for native and sand-based fields. For turfgrass establishing on native or sand-based soils, soluble sources of N fertilizer should be applied with a goal of delivering approximately 0.25 lb N per 1,000 ft2 per week. To reduce the frequency of applications of soluble fertilizers on sand-based soils and to reduce the loss of soluble N from leaching through the sand profile, the grow-in fertility program is commonly supplemented with nitrogen. These nitrogen sources are typically 50% or greater slow-release in order to provide uniform nitrogen release for a period of six to 10 weeks. This usage maintains consistent N feeding to the developing turfgrass. The concept also applies to native soils in terms of optimizing N use efficiency, but it is not as critical given the limited N leaching potential of the native soil.
Micronutrients may be beneficial during establishment, especially on sandy or high pH soils with low nutrient holding capacity, based on soil tests. Grow-in fertility programs under these conditions often include a micronutrient package. Periodic tissue testing is the most effective way to determine deficiencies on established turfgrass.
Light and frequent irrigation is required throughout the turfgrass establishment phase. Seeded fields should be moist on the surface and down to 0.25” in depth until germination. If seed mixtures are used, germination of all the species needs to be considered as well as field conditions and weather. Once all species have germinated, irrigation frequency should be reduced while the duration of the irrigation event is increased. Sodded fields should be irrigated as the sod takes root. Rooting should be checked by lightly pulling a sod corner. Irrigation frequency can be reduced when the sod cannot be pulled back from the soil surface.
Turfgrass covers are an excellent tool to extend color at least four to six weeks in the fall and encourage spring greening by one to two months (Goatley et al. 2005). On newly planted or renovated fields, turfgrass covers can also enhance seedling development and sod rooting in winter in some regions of the country. Covers may also help protect turfgrasses from frost or freeze damage. Covers should also be considered to encourage and accelerate as much off-season recuperation as possible for high wear areas on both warm season and cool season fields. Covered sports fields protect crowns/stolons/rhizomes from freezing temperatures, reducing the potential for winter damage from cold, desiccating winter winds.
The stimulation of turfgrass growth by the use of covers also requires special attention by the sports field manager, as pests also respond to the enhanced temperatures and moisture. Depending on environmental conditions and the blanket’s characteristics, a fungicide treatment might be necessary on cool season or ryegrass-overseeded bermudagrass fields that remain covered for several weeks. More information on using covers on bermudagrass fields is published in the Virginia Cooperative Extension publication Optimizing Bermudagrass Athletic Field Winter Survival in the Transition Zone.
Turfgrass Establishment Best Management Practices
Turfgrass Selection Best Management Practices
Work with university Extension specialists as needed to evaluate selection recommendations.
Select cultivars that are adapted to the sport, field characteristics, maintenance regimes, pest resistance, and spring or fall transition needs. Also consider other desired characteristics such as vigor, tolerance to environmental extremes, wear tolerance, speed of recovery, and shade tolerance (where applicable).
Develop and implement strategies, such as overseeding, hydro-seeding, or sodding to effectively control sediment, minimize the loss of topsoil, and protect water quality.
Turfgrass Establishment Best Management Practices
Ensure erosion and sediment control devices are in place and properly maintained.
Seed cool season grasses in the timeframe that allows for optimal seed germination (typically early August to late September) and for development well before cold temperatures significantly slow growth prior to winter.
Anticipate the wear on known heavy traffic areas by reseeding heavily and often for uniform playing surfaces.
Establish turfgrass sod when plants are actively growing so the sod will root or “knit” down into the soil as quickly as possible.
Fill gaps in sod seams with soil or sand to provide a uniform surface.
Overseeding Best Management Practices
Where allowed by regulations and ordinances, use seedling compatible, selective pre- emergence herbicides at the appropriate time to reduce weed competition and improve the chance of success with seeding establishment during the spring.
Balance fertility programs between the needs of both the cool season and warm season grasses and apply fertilizers only during periods of active turfgrass growth.
Consider the germination rate of the turfgrass species and cultivar in the timing of the overseeding event.
Warm Season Fields
o Time overseeding events on warm season bermudagrass when night temperatures are consistently around 50°F, two to three weeks prior to the first killing frost.
o Chemically or mechanically transition from ryegrass to bermudagrass as soon as possible upon the completion of spring sports to avoid weakening the bermudagrass from competition.
Cool Season Fields
o Overseed cool season fields to provide a better playing surface for current season play and increase turfgrass density for future seasons. o Utilize improved varieties of cool season species to maximize turfgrass performance while limiting the need for inputs (e.g., fertilizer, water, pesticides).
o Utilize university Extension specialists to make recommendations for cool season seed mixtures.
Cultural Practices Best Management Practices
If necessary and allowed by regulations and ordinances, apply a fertilizer containing phosphorus at the time of seeding. An additional application should be applied if soil or tissue tests demonstrate the need.
Nitrogen and sufficient water are essential during establishment. Light and frequent applications of nutrients and water are most desirable. A slow-release nitrogen source will provide a consistent release of nutrients.
Allow the turfgrass to initially grow one-third to one-half higher than the desired HOC before beginning to mow and never remove more than one-third of the turfgrass leaf at mowing.
Keep mower blades sharp. Dull mower blades may dislodge or damage young grass.
Consider mowing with a walk-behind mower rather than a heavier riding mower to avoid making wheel track depressions in the soil.
Delay watering prior to mowing to help the soil dry and to better tolerate the weight of the mower.