07 - CULTURAL PRACTICES
Cultural practices are essential to providing a high-quality playing surface.
Examples of these practices include mowing, soil aerification, tree and shade management, and organic matter management (i.e., verticutting and other methods of thatch management). Turfgrass cultivar, climate, budget, and golf course expectations are all important aspects of necessary BMPs and inform how they are best carried out.
Mowing
When developing a management plan, mowing is one of the most fundamental cultural practices to include. Turfgrass growth rate, texture, density, color, wear tolerance, and root development are all affected by mowing practices.
When it comes to turfgrass, mower types, frequency, and mowing height matter. More frequent mowing increases shoot density and tillering, but it also decreases root and rhizome growth due to the stress related to leaf tissue removal. Conversely, mowing too infrequently leads to alternating vegetative growth cycles followed by scalping which can further deplete the plant’s food reserves.
There are several factors that determine proper mowing height including frequency, shade, root growth, abiotic and biotic stress, mowing equipment, and season of the year. The impact of these factors depends on which turfgrass species and/or cultivar is being managed and the intended use of the area. Improper mowing practices can result in weakened turfgrass with poor quality and density.
Maintaining an optimal root-to-shoot ratio is crucial. Mowing turfgrass too low at one time can cause an imbalance between the root system and the residual vegetative tissue. This will leave more roots present than the plant physiologically needs and cause the plant to shed unnecessary roots. Turfgrass cut too short will result in plants that need ample time to provide enough food to produce shoot tissue for future photosynthesis. It is best not to remove more than 30 to 40 percent of the leaf area in a single mowing as the root growth will be least affected.
Proper mowing and rootzone management are foundational practices for healthy turfgrass.
Mowing frequency required during active growth, conforming to 1/3 rule based on mowing heights
Source: Adapted from Best Management Practices for New England Golf Courses, February 2020
Best Management Practices
Maintain proper mowing heights and frequency within the ranges adapted for the species and cultivars being managed.
Increase mowing frequency during periods of rapid growth and decrease frequency during dry and stressful periods.
For turfgrass that has grown too tall, avoid mowing down to the proper height all at one time. Severe scalping reduces density and can result in significant reduction in root growth. Mow tall grass frequently, gradually decreasing height until the proper height of cut is reached.
To aid and improve the health of shaded turfgrass, mowing height should be increased by a minimum of 30%. When turfgrass is shaded, growth is affected by the plant filtering out photosynthetically active radiation. This causes turfgrass to grow upright in an effort to consume the light to meet the plant’s photosynthetic needs.
Using plant growth regulators (PGRs) for grasses grown in shaded areas has been shown to improve overall turfgrass health.
Prolonged cloudy weather and periods of drought significantly impact turfgrass health. During these periods, increasing mowing heights to the maximum that use will allow will increase the plant’s rooting depth and photosynthetic capacity.
Use proper mowing equipment; reel mowers produce the best quality and are suited for maintaining a height of cut below 1.5 inches.
Rotary mowers deliver adequate cutting quality for maintaining turfgrass at a height of cut above one inch and are more versatile when compared to reel mowers on uneven terrain.
Maintain clean, sharp blades and proper adjustment. Dull blades will shred leaf tissue resulting in increased water loss and potential for diseases to develop.
Flail mowers are most commonly used for maintaining utility turfgrass areas that are rarely mowed and have low aesthetic requirements.
Mowing patterns influence functional characteristics of a turfgrass surface in addition to aesthetic.
Alternating between mowing and rolling can reduce stress on turfgrass, especially putting greens.
Turfgrass clippings contain significant amounts of potassium and phosphorus in addition to 2%-4% nitrogen on a dry-weight basis which is a source of nutrients. Clippings should be properly handled as nutrients can be a source of stormwater pollution.
Return grass clippings to the site during mowing, except when underlying turfgrass plants could be smothered by a large number of clippings and when clippings on greens have a negative impact on play and functional use, such as affecting ball roll. In such cases, grass clippings should be removed.
Grass clippings should be removed during periods of pest infestation and/or weed seed production to reduce the spread of weeds, diseases, and insects. Mowers should be cleaned following use on an area infested with a pest issue. In the case of disease (e.g., Pythium), sterilization may be recommended using a bleach dilution.
Properly dispose of collected clippings in order to avoid unpleasant odors near play areas and prevent fire hazards. Consider composting or dispersing healthy clippings evenly on natural areas where they can organically decompose. Do not compost or dispose of clippings on impervious surfaces or near ponds and streams.
Mowing Directions
It is important for growing grass to keep an upright growth habit, which provides a smooth playing surface. This can be achieved with varying mowing directions. Rotating directions prevents turfgrass from lying over which will cause it to grow in the direction that it is being mowed. This practice prevents other issues such as rutting and “grain.” “Grain” is the result of lateral growth habit. This effects the playing surface by influencing the ball to roll in the same direction the grass is growing and causes inconsistent ball roll speed. In addition, this impedes the mower’s ability to cut effectively which leads to the accumulation of thatch.
Another downside of a singular mowing direction is rutting. This causes wear and soil compaction due to driving the same area repeatedly. As a solution, golf courses can provide a chart of daily mowing directions. Using clock positions as a template is one method to creating a daily varied mowing pattern. For instance, Monday’s direction is 12 to 6, Tuesday is 3 to 9, Wednesday is 8 to 2, and Thursday is 10 to 4. By varying mowing directions, operators can also create a checkerboard pattern, giving them more visibility of the lines.
Avoid the use of heavy mowers or other equipment on saturated soil – as this can increase the likelihood of rutting/compaction.
Types of Mowers
When it comes to best practices for mowing turfgrass, using appropriate equipment is essential. Rotary mowers and reel mowers are the best cutting units to get the job done.
Rotary mowers are best suited for maintaining grass at a higher height-of-cut. This mower’s blades are mounted horizontally to a vertical shaft that spins at high speeds. The sharp, highspeed blade cuts through the leaf blade like a knife as opposed to a scissor cut. Rotary mowers are not able to mow shorter than one inch, which can be a disadvantage. Maintain a sharp blade for best results, however it is always important to be cautious of swinging blade-related danger.
Reel mowers are best for areas maintained at a shorter height-of-cut like golf course greens. This is a cylinder mower with eight to 16 evenly spaced blades and a sharp stationary bedknife mounted beneath the reel. As the cylinder spins, the reel mower creates a scissor cut between the blade and bedknife. These mowers have the advantage of saving fuel and allowing for battery operated options as they require less power. Reel mowers will need frequent adjustment and maintenance in order to get the lowest mowing height and highest cut quality. The skill needed for proper adjustment and maintenance can be a disadvantage in addition to the reel mowers limited range of height-of-cut options.
Height of Cut
There are various types of playing surfaces on every golf course. Each surface requires different mowing frequencies and height-of-cut. Factors that influence mowing practices include seasonal changes, air and soil temperatures, and how quickly the grass is growing. For example, cooler temperatures and shorter days in the winter reduce the plant’s opportunity for photosynthesis. This results in slower growing speeds that require less mowing. Warmer temperatures and longer days in the summer months allows turfgrass the opportunity to photosynthesize which creates rapid growth. These conditions create the need for additional mowing. As a general guideline, it’s important not to remove more than one-third of the top growth in a single mowing. To achieve the desired height-of-cut, this may require more frequent mowing.
Each surface will require appropriate equipment in order to maintain an optimal golf course. The best equipment for roughs is a rotary mower set between one and two inches for height of cut and mowed once or twice weekly on average. Other areas of the course require reel mowers. Fairway, tee, and approaches should be kept at a height-of-cut of 0.5 inches or less for ideal playability. Depending on the turfgrass’ growing speed, these areas will likely need mowing two or three times weekly.
Putting greens are the most important feature of the golf course. To ensure an ideal playing surface, greens demand the highest priority and maintenance. The average mowing height for greens ranges from .07 to .125 inches. Maintaining this height-of-cut means daily upkeep and mowing are needed. Reel mowers are best suited for the job. Keeping the equipment’s blades sharpened and regular adjustments will result in a quality cut.
Rolling
Rolling putting greens daily will push down imperfections, keeping the surface smooth. This helps increase putting speeds for improved ball roll all without the need to lower the height-of-cut. Supplementing rolling with mowing allows one to raise the height-of-cut which will result in healthier turfgrass.
Research has found that preventing weeds and occurrence of disease are other benefits of rolling. Lightweight rollers are recommended. If a heavy roller is used, there are risks of soil compaction and additional aerification may be required to relieve soil issues.
Plant Growth Regulators (PGRs)
Golf course superintendents commonly use PGRs on putting greens to reduce turfgrass shoot growth to decrease mowing requirements, which can improve ball roll. Another benefit is the maintenance of green speed throughout the day, which can be enjoyed by golfers playing later in the evening. PGRs are also used to reduce irrigation, and fertility needs; control seed heads; as well as improve density, color, stress tolerance, and overall turfgrass quality.
PGRs are divided into six classes based on mode of action. Table 1 shows the most widely used PGRs.
Gibberellic acid (GA) inhibitors suppress GA in the plant, reducing turfgrass clipping yield. GA suppression will wane after time causing a potential rebound effect where the turfgrass goes through a period of increased clipping yield. Reapplications before the rebound phase occurs are necessary to help maintain suppression.
Track growing degree days (GDDs) following the application of a PGR. Using GDDs prevents the over-regulation of turfgrass, which can cause significant damage, or conversely, the rebound phase. Degradation levels of each PGR type are based on the rate applied and seasonal temperature levels. Charts showing PGR reapplication thresholds are available to help determine the number of GDDs before applying the next application.
Best Management Practices
Use PGRs on playing surfaces to aid with improving overall turfgrass quality and reduce irrigation needs.
To find the most effective PGR application timing, use GDDs thresholds indicated on published charts.
Use PGRs to help gain green speed; this is more effective and results in healthier turfgrass than excessively low cutting heights or very frequent mowing schedules.
Use GA inhibitors to reduce clipping yields, improve turfgrass quality, and help lower maintenance costs.
Use seaweed extracts and humic acids to help improve turfgrass quality while reducing N inputs and avoiding excessive growth.
Table 1. PGR chemical classes, modes of action, chemical names, and products.
Source: Adapted from Connecticut Golf Industry Best Management Practices Guide, 2020
Cultivation
Cultivation practices are essential to golf course management. High traffic areas like putting greens, fairways, and tees will experience deterioration with routine use. Soil issues related to everyday use will be limited to the top three inches of the soil profile. Other negative impacts of routine use include compacted soil and thatch accumulation. Properly managing these issues will enhance plant health by increasing nutrient and water uptake, encouraging root growth, promoting atmospheric gas exchange, and reducing thatch accumulation.
Aerification
Occasional tilling is a customary soil practice for correcting problems related to soil compaction. Turfgrass will not allow for serious physical disruption from tilling without destroying the playing surface. Core aerification is used for managing thatch and soil compaction with reduced physical disturbance. This method also successfully improves drainage. In conjunction with core aerification, applying light sand frequently will help control thatch, smooth playing surfaces, and potentially alter the soil’s physical characteristics.
Solid tine aerification is also a method to reduce soil compaction. Other forms of aerification and cultivation include air-injection, sand-injection, water-injection, slicing, drill-and-fill, and fraise mowing.
Vertical Mowing
Thatch accumulation can commonly occur in areas with less traffic. Over accumulation of thatch and other organic matter can cause a host of challenges including increased insect activity, disease, scalping, reduced water infiltration, root growth reduction and an overall undesirable playing surface. Vertical mowing is the best method for managing grain and removing accumulated thatch. Mower groomers serve as small vertical mowers attached to the front of the reels which serrate stolons to improve plant density and manage grain.
Comparison of Methods Used to Selectively Cultivate Turf
Best Management Practices
Core aerification is the removal of small cores, typically 0.25 to 0.75 inch in diameter, from the soil profile. Core aerification programs should only remove 15% to 20% of the surface area on an annual basis. High traffic areas may need two to four or more core aerifications annually. For help determining the area’s specific needs reference the International Sports Turf Research Center (ISTRC) http://www.istrc.com/.
Watch for wear patterns that affect the quality of the turfgrass, cart traffic on fairways may cause compaction which can affect turfgrass health.
Perform core aerification when turfgrass is actively growing for quicker surface recovery.
To prevent the formation of compacted layers in the soil profile from cultivation, vary the depth of aerification by changing tine length during each event.
Solid-tine aerification is a method to manage soil compaction with minimal surface disruption. Since this method does not remove soil from the profile, it is only a temporary solution and does not aid in thatch management.
Drill-and-fill aerification brings soil to the surface and distributes it into the canopy by drilling deep holes in the soil profile with drill bits. Using sand or other root-zone materials to backfill holes allows the replacement of heavy soil in an effort to increase water infiltration in the soil profile.
Slicing is best performed on moist soil and can reduce soil compaction and promote water infiltration with little surface damage. It is faster than core aerification but not as effective.
Spiking also reduces soil compaction by breaking up crusts on the surface and disrupting algae layers to allow better water infiltration.
Setting a vertical mower to a depth that light cuts the surface can reduce the grain of putting greens. To stimulate new growth, set the verticutter to a deeper depth penetration to cut through stolons and rhizomes. Depth for thatch removal should be set to reach the bottom of the thatch layer extending beneath it into the soil surface.
Vertical mowing should be initiated when thatch level reaches greater than 0.25 inch in depth; for putting greens, shallow vertical mowing should be initiated at least monthly to avoid accumulation.
Aggressive dethatching with a verticutter is not recommended for putting greens as this causes damage that requires extensive recovery time.
Topdressing playing surfaces with sand after heavy vertical mowing and core aerification help turfgrass to recover. Rates are determined by how well the turfgrass canopy absorbs the material without risk of burying the plant. Typical rates range from a depth of 0.125 to 0.25 inch.
Topdressing
Topdressing is the application of desirable rootzone material, rootzone amendment, or pure sand to the turfgrass surface to help the crown of the plant remain as close to the soil surface as possible. This practice encourages maximum root development, water, and air movement; and minimizes pest susceptibility. Before application, remove thatch and other organic matter through appropriate cultivation practices.
Particle size must be compatible with the existing rootzone material in order to be effective. In other words, the topdressing should have the same size distribution as the construction mix or have a coarser texture. If the grain used is finer than the original sand mix material, it can have the undesired result of excessive moisture retention in the topdressing layer, due to low rootzone infiltration rates. Modifying the top three inches of soil with topdressing increases infiltration rates and reduces runoff.
Objectives of Sand Topdressing
• Dilute thatch accumulation
• Smooth the playing surface
• Maintain surface drainage
• Increase infiltration
• Increase soil macroporosity at the surface
• Increase surface firmness
Best Management Practices
Throughout the growing season, apply light topdressing sand frequently (every seven to 14 days) or match the applications with the plant growth potential. This will help control thatch and smooth uneven playing surfaces on putting greens.
Using finer materials may cause layering and reduce water infiltration.
Weed-free topdressing material with a similar particle size to the underlying root is recommended.
During active turfgrass growth, increase the amount of topdressing to putting greens in conjunction with aggressive cultivation practices. Harvest cores and refill the holes with topdressing.
Lab test topdressing material with the Standard Test Method for Particle Size Analysis and Sand Shape Grading of Golf Course Putting Green and Sport Field Rootzone Mixes known as ASTM F1632.
Include 15 to 20 subsamples at 4-inch depth. If previously top-dressed, use the current topdressing layer depth. To determine suitability of topdressing material, compare test results to USGA guidelines and the prospective topdressing material to determine compatibility.
To ensure the topdressing material meets USGA guidelines for hydraulic conductivity, lab test the material with the Standard Test Methods for Saturated Hydraulic Conductivity, Water Retention, Porosity, and Bulk Density of Putting Green and Sports Turf Rootzones or ASTM F1815.
Accredited labs for testing:
International Sports Turf Research Center http://www.istrc.com/
Turf & Soil Diagnostics https://www.turfdiag.com/
Thomas Turf Services soiltest@thomasturf.com
Overseeding Warm-Season Turfgrass
Overseeding can help maintain turfgrass color and playability during the fall and winter by establishing a temporary cool-season grass into the warm-season base when the warm-season grass enters dormancy. This process can also improve the biological and microbiological soil activity by prolonging the period of time turfgrass is actively growing throughout the year.
Effective overseeding programs require year-long planning and involve all facets of root-zone cultivation and weed control with the goal of upholding warm-season turfgrass health while allowing the cool-season grass species to be established. Overseeding increases the need for irrigation and routine mowing which can cause significant thinning of the base grass during spring transition. The cool-season overseed also acts as a shade crop restricting sunlight for the warm-season base grass to reestablish in the spring.
Best Management Practices
Thatch depth greater than 0.5 inch in the warm-season turfgrass base will prevent good seed-to-soil contact and will result in sporadic germination and establishment. Remove thatch as part of an active cultivation program before overseeding.
Reduce or eliminate fertilization of the base grass three to four weeks before the planned seeding date to minimize growth and competition.
Core-aerify the soil four to six weeks before the planned overseeding date to open turfgrass canopy and aid in uniform establishment of overseeded grass.
Select grass species/cultivars that are adapted to the desired use, taking note of disease resistance, and spring transition traits. Cultivars with improved heat tolerance can delay spring transition and create increased competition for water, nutrients, and light with the warm-season turfgrass base.
The use of Growth Regulators prior to overseeding is a common practice and allows for less severe removal on existing warm season grasses to increase establishment and enhance Spring transition.
Irrigate newly planted overseed to maintain constant moisture levels, not allowing the soil surface to dry out. Gradually reduce irrigation once the seedlings have been mowed.
Do not fertilize with N immediately before or during establishment of overseed as the N may encourage warm-season turfgrass competition and increase disease potential.
Move hole locations on putting greens daily during the establishment period to minimize damage to seedlings from foot traffic.
Reduce fertilizer rates in spring to slow growth of overseeded grass. Once warm-season turfgrass regrowth is apparent, restore fertilizer applications to stimulate growth of the warm-season turfgrass.
Colorants (dyes and pigments) can be used to provide winter color to dormant grasses.
Overseeding practices can generate significant dust that may require dust control measures.
Bunkers
Bunkers are designed specifically for the golf course based on playability and level of management desired. These hazards serve more than one purpose by providing an obstacle for golfers while offering aesthetic appeal. Some consider bunkers to be the course’s personality.
A bunker is made up of a drainage component, a liner, and top sand. The drainage system is installed on the bunker floor followed by the liner installed on the base. Liners aid in the prevention of contaminated sand and reduce sand from washing down banks from heavy rain. The top sand layer can be firmer or softer depending on the drainage capacity, or how quickly moisture clears the bunker floor.
When selecting sand, it is recommended to perform a sand analysis with an accredited lab as sand selection influences playability. There are several important parameters to consider when selecting potential sand. Infiltration rate determines favorable sand with a recommended rate of at least 30 inches per hour. A penetrometer reading is a good predictor of the sand’s tendency to result in fried egg or plugged lies. Sand depth with an average of 4 to 6 inches at the base of the bunker and 2 to 3 inches on the faces is recommended by the USGA. Weather and maintenance are other parameters to consider. To ensure the best sand selection, acquire several potential sands and construct test bunkers or test bunkers at other golf courses. Angle of repose should be tested for the sand that is to be used to ensure the bunker “faces” are not too steep to hold the desired sand in place.
Bunker maintenance includes regular raking. There are many types of rakes and methods that create an optimal playing surface. Motorized raking equipment can be used on large bunkers, while small bunkers will need to be raked by hand. Firm bunker surfaces develop as a result of regular rainfall or irrigation and shallow raking. Soft bunker surfaces tend to develop from dry weather and deep raking.
Best Management Practices
Golfer clientele and maintenance costs will influence bunker designs. Constructing numerous bunkers and features such as intricate edges, revetted, and high flashed faces will increase costs and difficulty.
Extensive herringbone drainage and a quality bunker liner is recommended.
Avoid washout by shaping bunker surrounds so that surface water doesn’t drain into the bunker.
Install irrigation to water bunker banks and keep the sand from becoming too dry.
Construct test bunkers or visit other golf courses to help with sand selection.
Lab test prospective sand with an accredited lab when selecting bunker sand.
Sand depth of 4 to 6 inches on the bunker floor and 2 to 3 inches on the banks is best for playability.
Maintaining firmer bunker banks and a smooth, weed-free surface helps prevent “fried egg” lies.
Rake bunkers four times weekly for a consistent surface, with touch-ups in between to save labor.
Bunker banks should be mowed weekly and edged on a two to four-week interval.
Maintain proper depths by probing the sand about every two weeks depending on whether the bunkers are highly contoured or flat.
Dirty and contaminated bunkers can be refreshed by removing the top one or two inches of sand and replaced with new sand.
Fluff sand and improve playability when bunkers are too firm by using a motorized bunker rake with cultivating tines.
Golf course architects recommend rebuilding bunkers every seven years depending on condition.
Resources for Sand Analysis:
Turf & Soil Diagnostics
613 E. 1st Street
Linwood, KS 66052
Phone: (855) 769-4231
lab@turfdiag.com
Thomas Turf Services
11183 State Highway 30
College Station, TX 77845
Attn: Bob Yzaguirre
Phone: (979) 774-1600
Mobile: (979) 575-5701
soiltest@thomasturf.com
Shade Tree Management
Full sun is ideal for most turfgrasses. Heavily shaded areas have decreased air circulation and lack the opportunity for photosynthesis, leading to disease and pests. Problems should be identified and monitored with annual shade audits. Survey sun patterns throughout the year to determine which trees are blocking light from desired areas. Note the tree species, value, health, life expectancy, location, maintenance requirements, and safety concerns.
Increase airflow and light by removing branches as necessary. In the case of severe issues, select trees may also need to be removed. When planning tree planting, it is crucial to consider turfgrass plant health. Competing tree roots can cause turfgrass health and performance to suffer.
Best Management Practices
Tree limbs and roots can be pruned to reduce competition for nutrients, sunlight, and water.
Trees located near low mowed areas like greens and tees can disrupt turfgrass growth. Thin the tree’s canopy to promote growth or remove and/or relocate the tree if possible.
Survey sun angles throughout the year to understand how it affects plant health.
Annual shade audits should be performed to identify problems. Apps like “Sun Seeker” can be used to pinpoint the shade-causing trees.
Tree surveys can be conducted with an arborist to identify tree species, value, health, life expectancy, location, maintenance requirements, and safety concerns.
Where trees are intricate to design and playability; circulation fans are recommended to improve air circulation.
