6 - Mowing & Root Zone Management
Practices such as mowing, aerification, tree and shade management, and verticutting are keys to providing a high-quality playing surface. Turf variety, climate, budget, and golf course standards all inform what BMPs are needed and how they are carried out.
Proper mowing practices and root zone management are cornerstones for healthy turf. These practices work hand-in-hand with IPM, water and irrigation management, plus golf course playability.
Mowing
When developing a management plan, mowing is one of the most important practices to consider. Turf growth, texture, density, color, wear tolerance, and root development are all affected by mowing practices.
Frequency and mowing height matter. Mowing too frequently increases shoot density and tillering, as well as decreases root and rhizome growth due to plant stress related to leaf tissue removal. Infrequent mowing results in alternating vegetative growth cycles followed by scalping, leading to further depletion of the plant’s food reserves.
Based on the species/cultivar being managed and the intended use of the site, there are several factors that determine proper mowing height including frequency, shade, root growth, abiotic and biotic stress, mowing equipment, and time of the year. Improper mowing practices will result in weakened turfgrass with poor quality and density.
It is crucial that an optimal root-to-shoot ratio be maintained. Mowing too low will result in turfgrass plants that need a significant amount of time in order to provide the food required to produce shoot tissue for future photosynthesis. Mowing turf too low at one time can lead to 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. It is best to remove no more than 30 to 40 percent of the leaf area in a single mowing as the root growth will be least affected.
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 turf that has grown too tall, avoid mowing down to the proper height all at one time. This kind of severe scalping reduces density and can result in significant reduction in root growth. Mow tall grass frequently, gradually decreasing the height until the proper height of cut is reached
When turfgrass is shaded, its growth is affected by the plant filtering out photosynthetically active radiation; this will cause the turfgrass to grow upright in an effort to consume the light needed to meet the plant’s photosynthetic needs; to aid and improve the health of shaded turfgrass, mowing height should be increased by a minimum of 30%
Using plant growth regulators for grasses grown in shaded areas is a management tool that has been shown to improve overall turf health
Periods of drought are environmental stressors that significantly impact turf health - during these periods, increasing mowing heights to the maximum that use will allow will help increase the plant’s rooting depth and photosynthetic capacity
It is important to use proper mowing equipment; reel mowers produce the best quality and are suited for maintaining a height of cut below 1.5 inches
For maintaining turfgrass at a height of cut above one inch, rotary mowers deliver adequate cutting quality; rotary mowers are more versatile when compared to reel mowers on uneven terrain
Maintain 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 turf areas that are rarely mowed and have low aesthetic requirements
Mowing patterns influence functional characteristics of a turf surface in addition to aesthetic
When turfgrass shows signs of stress, alternate between mowing and rolling
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; these clippings should be properly handled as these nutrients can also be a source of pollution
Return grass clippings to the site during the mowing process except in the case where underlying turfgrass plants could be smothered by a large number of clippings and when clippings on golf 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 also be removed during seasons of weed seed production to reduce the spread of weeds
Properly dispose of collected clippings in order to avoid unpleasant odors near play areas and prevent fire hazards; consider composting or dispersing clippings evenly on natural areas where they can organically decompose without accumulation; 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, thus providing a smooth playing surface. This is achieved with varying mowing directions. Rotating directions prevents turfgrass from lying over which causes it to grow in the direction that it’s being mowed. It also gives operators more visibility of lines.
Varying mowing directions prevents other issues such as “grain”, marcelling, and rutting. “Grain” is the result of lateral growth habit, which effects the playing surface by influencing the ball to roll in the same direction the grass is growing and inconsistent ball roll speed. In addition, the mower will not cut effectively causing the accumulation of thatch which results in marcelling over time. Marcelling is the washboard or wavy appearance of turfgrass that adversely affects playing conditions. Rutting is another downside of a singular mowing direction as tires driving the same area repeatedly causes wear and soil compaction. As a solution, many golf courses provide a chart of daily mowing directions. One method is to use clock positions to determine the daily 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.
Types of Mowers
Using appropriate equipment is essential when it comes to mowing turf. Rotary mowers and reel mowers are the best cutting units for the job.
Rotary mowers are best suited for grass that is maintained at a higher height-of-cut. This mower’s blades are mounted horizontally to a vertical shaft that spins at high speeds. The sharp, speedy blade impacts the turf by cutting the leaf blade like a knife as opposed to a scissor cut. It is important to maintain a sharp blade. Disadvantages of the rotary mower include the inability to mow shorter than one inch and swinging blade-related danger.
Reel mowers are used for other areas that are maintained at a shorter height-of-cut such as golf course greens, tees, and fairways. This is a cylinder mower with eight to 16 evenly spaced blades with a sharp stationary bedknife mounted beneath the reel. Unlike the rotary mower, reel mowers create a scissor cut between the blade and bedknife as the cylinder spins. These mowers save fuel and allow for battery operated options as they require less power. It is important to properly adjust and maintain reel mowers in order to get the lowest mowing height and highest cut quality. Disadvantages of reel mowers are height-of-cut options, skill needed for proper adjustment which must be done in accordance with the manufacturer, and maintenance.
Height of Cut
Golf courses consist of various types of playing surface which require different mowing frequencies and height-of-cut. There are other factors that influence mowing practices such as time of year, temperatures, and the grass’ growing speed. For example, early spring and late fall bring cooler temperatures and shorter days. This reduces the plant’s opportunity for photosynthesis resulting in slower growing speeds and require less mowing. With warmer temperatures and longer days in the summer months, grass has the opportunity to photosynthesize causing rapid growth and increases 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.
Using the appropriate equipment for differing surfaces helps create a more optimal golf course. For roughs, set a rotary mower between two and three inches for height-of-cut and mow once or twice weekly on average. Other areas of the course require reel mowers such areas as fairways, tees, and approaches. Depending on how quickly the turfgrass is growing, these areas will likely need mowing two or three times weekly.
Since golf course greens are the most important feature, they demand the highest priority with daily maintenance and mowing. Reel mowers are a must for course greens as they require lower mowing heights. The average mowing height for greens ranges from .07 to .125 inches, each golf course will determine the best mowing height for the respective course. The key is a height that can be maintained to provide smooth and constant green speed. Occasionally, a roller can substitute mowing. It’s important that reel mower blades are sharpened and adjusted often for cut quality. These practices will ensure an ideal playing surface.
Rolling
Daily rolling of a putting green can increase putting speeds for improved ball roll, without lowering the height-of-cut. Any time height-of-cut is raised, turf is healthier; research has shown that rolling contributes to less weeds and occurrence of disease. Rolling also helps improve smoothness of the ball roll by pushing down imperfections.
GA inhibitors affect turfgrass growth by reducing clipping yield through suppression of GA in the plant. After a period of time, the suppression will wane, and turf will go through a period of increased clipping yield, which is referred to as the rebound effect. To help maintain suppression, reapplications are necessary before the rebound phase occurs. This is accomplished by tracking growing degree days (GDDs) following the application of a PGR. Each PGR type has its own level of degradation based on the rate applied and temperature levels at the time of year. Charts showing PGR reapplication thresholds are available to help determine the number of GDDs before applying the next application. Rather than a calendar-based application schedule, use of GDDs prevents the over-regulation of turf, which can cause significant damage, or conversely, the rebound phase.
Best Management Practices
Use PGRs on playing surfaces to aid with improving overall turf 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 turf than excessively low cutting heights or very frequent mowing schedules
Use GA inhibitors to reduce clipping yields, improve turf quality, and help lower maintenance costs
Use seaweed extracts and humic acids to help improve turf quality while reducing N inputs and avoiding excessive growth
Cultivation
When it comes to golf course turf management, cultivation practices are essential. Putting greens, fairways, and tees experience deterioration as these areas experience higher traffic with routine use. Negative impacts of routine use include compacted soil and thatch accumulation. Soil issues caused by excessive use will typically be limited to the top three inches of the soil profile. Persistently managing these issues will enhance plant health by improving nutrient and water uptake, reducing root penetration, promoting atmospheric gas exchange, and removing thatch accumulation.
Aerification
Customary soil practices call for periodic tilling in order to correct problems related to soil compaction. Turfgrass does not allow for significant physical disruption from tilling without destroying the playing surface. A practice used to manage soil compaction with reduced physical disturbance is core aerification. This method helps manages soil compaction and improves drainage. In conjunction with core or solid tine aerification, applying light sand frequently will help control thatch, smooth playing surfaces, and potentially alter the soil’s physical characteristics.
Verticutting
Thatch accumulation can commonly occur in areas with less traffic. Over accumulation of thatch and other organic matter may result in increased insect activity, disease, scalping, along with reduced water infiltration, root growth reduction and overall undesirable playing surface. Verticutting, otherwise known as vertical mowing, can help manage grain and remove accumulated thatch. Groomers are a miniature vertical mower attached to the front of the reels which cut through stolons in order to improve plant density and manage grain.
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/
Perform core aerification when turfgrass is actively growing to recover surface density more quickly
To prevent the formation of compacted layers in the soil profile from cultivation, vary the depth of aerification with varying length tines during each event
To temporarily reduce soil compaction when grass growth rate is slower, use solid tines; this helps soften hard turf surfaces with less disruption - since this method does not remove soil from the profile, it is only a temporary solution
Solid tine aeration has also proven to be a replacement for core aeration on sand root zones and when organic matter levels are in check
Deep-drill 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
Sand injection is another form of aeration using water-based injection to create aeration holes through the root zone and simultaneously fill holes with sand
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 verticutter to a depth that nicks the turf’s surface can reduce the grain of putting greens; to stimulate new growth, set the verticutter to an increased depth of penetration to cut through stolons and rhizomes and remove thatch; 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 0.25 to 0.5 inch in depth; for putting greens, shallow vertical mowing (shallow enough to avoid intermixing the native soil and the sand topdressing layer) should be initiated at least monthly to avoid thatch accumulation
Topdressing playing surfaces with sand after heavy vertical mowing and core aerification help turf to recover; rates are determined by how well the turf canopy absorbs the material without risk of burying the plant; typical rates range from a depth of 0.125 to 0.25 inch
Additional information: https://www.usga.org/articles/2012/10/course-care-thatch-control-key-to-firm-resilient-fairways-21474850692.html
Topdressing
Managing turfgrass with topdressing encourages maximum root development, water, and air movement; and minimizes pest susceptibility. Topdressing achieves these benefits when desirable rootzone material, or sand mixture, is added to the surface. This helps the crown of the plant to remain as close to the soil surface as possible. Before application, thatch and other organic matter need to be removed through cultivation practices.
Particle size is important when it comes to topdressing because it must be compatible with the existing rootzone material to be effective. If texture of the materials used is finer than the original sand mix, this can have the undesired result of excessive moisture retention in the topdressing layer, due to lower rootzone infiltration rates. Modifying the top three inches of soil with topdressing creates better infiltration rates and reduces runoff. Sand should be tested by a Certified Lab before implementing a topdressing program or changing material.
“Particles used in the topdressing should have the same size distribution as the construction mix or have a texture that is coarser.”
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
Weed-free topdressing material with a similar particle size to the underlying rootzone is recommended; using finer materials may cause layering and reduce water infiltration
In the spring and fall, 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 topdressed, use the current topdressing layer depth; to determine the suitability of the 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
Turf & Soil Diagnostics
Bunkers
Bunkers are designed to create aesthetic appeal that some consider to be the course’s personality and serve as a strategic hazard that provides an obstacle for golfers. Golf course architects plan bunkers specifically based on shot values, playability, and level of management desired.
A bunker is made up of a drainage component, a liner in some cases (optional), and top sand. The drainage system is installed within the bunker floor. Depending on the capacity of the drainage, or how quickly moisture clears the bunker floor, the sand layer may be softer or firmer. When a liner is installed on the base of the bunker it helps to remove water quickly, reduces sand from washing down steep banks, and aids in avoiding contaminated sand due to subsoil infiltration.
Sand selection influences playability, it is recommended to perform a sand analysis with an accredited lab. There are several important parameters to consider when selecting potential sand:
Particle size analysis
Particle shape (angularity and sphericity)
Uniformity coefficient
Angle of repose
Acid reaction
Color
Climate
A penetrometer reading is a good predictor of the sand’s tendency to result in fried egg or plugged lies. Infiltration rate is another parameter that determines favorable sand. A rate of at least 30 inches per hour is recommended. As it relates to depth, factors like moisture release curves and moisture column tests should be included to find optimum sand depth especially with the use of porous aggregate bunker liners. An average sand depth of 4 to 6 inches at the base of the bunker and 2 to 3 inches on the faces is recommended by the USGA, but can vary based on sand type and incorporation of a liner system. Acquiring several potential sands and constructing test bunkers or testing bunkers at other golf courses is recommended before sand selection when possible.
Long-term maintenance should always be considered in bunker design and construction. Bunkers need raking and there are many types of rakes and methods that can be used to create a desired playing surface. Larger bunkers will allow for motorized raking while smaller bunkers may need to be raked by hand. Firmer bunker surfaces are desired by most golfers and will develop with regular rainfall or irrigation and shallow or minimized raking. Softer bunker surfaces, which result in buried lies, result from dry weather and deep or continuous raking, and should be avoided.
Best Management Practices
Golfer clientele and maintenance costs will inform 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 washouts by shaping bunker surrounds so that surface water doesn’t drain into the bunker
Irrigating bunker banks can keep the sand from becoming too dry, but can be costly to install
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 a typical recommendation, but varies depending on sand type and construction method
Maintaining firmer bunker banks and bottoms will help prevent “fried egg” lies.
To maintain a consistent surface, lightly rake and limit 2 or 3 times per week if possible, performing touch-ups in between to save labor
Bunker banks should be mowed weekly and lightly edged on an as-needed basis.
Maintain proper depths by probing the sand about every two weeks depending on whether the bunkers are highly contoured or flat, or in a location of high use
Dirty and contaminated bunkers may sometimes be refreshed by removing the top one or two inches of sand and replaced with new sand
Turn sand over when bunkers are too firm by using a motorized bunker rake with cultivating tines
Studies indicate bunker sand should be replaced every five to seven years depending on condition; use of liners may extend this period
Resources for Sand Analysis:
Turf & Soil Diagnostics
613 E. 1st Street
Linwood, KS 66052
(855) 769-4231
lab@turfdiag.com
http://www.turfdiag.com/
Thomas Turf Services
11183 State Highway 30
College Station, TX 77845
Attn: Bob Yzaguirre
(979) 774-1600
http://thomasturf.com/
A. McNitt & SerenSoil Testing
1338 Deerfield Drive
State College, PA 16803
(610) 360-5985
andy@turfsoiltesting.com
tom@turfsoiltesting.com
http://www.turfsoiltesting.com
Shade and Tree Management
Most turfgrasses typically perform best in full sun. Heavily shaded areas have decreased air circulation and opportunity for photosynthesis which can lead to turf decline, disease, and pest issues. Annual shade audits are recommended to identify problems. Survey sun patterns throughout the year to determine which trees are blocking light from desired areas. Remove necessary branches to increase airflow and light. For severe issues, select trees may need to be removed.
Turfgrass plant health is the key consideration when planning tree planting and/or removal. Competing tree roots can cause turfgrass health and performance to suffer. Notate tree species, value, health, life expectancy, location, maintenance requirements, and safety concerns.
Best Management Practices
Tree limbs and roots can be pruned in order to reduce competition for nutrients, sunlight, and water
Trees located near low mowed areas like greens and tees can disrupt turf 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
