8 - Cultural Practices
Mowing
Mowing is the most basic yet most important cultural practice to consider when developing a management plan. Mowing practices have an impact on turf growth, density, texture, color, root development, and wear tolerance. Frequent mowing will increase shoot density and tillering. It will also decrease root and rhizome growth as a result of plant stress associated with removal of leaf tissue. Infrequent mowing results in alternating cycles of vegetative growth followed by scalping, which further depletes food reserves of the plants.
Proper mowing height is a function of the species/cultivar being managed and the intended use of the site. Other factors influencing mowing height include mowing frequency, shade, mowing equipment, time of year, root growth, and abiotic and biotic stress
Maintaining an optimal root-to-shoot ratio is critical. Turfgrass plants that are mowed too low will require a substantial amount of time to provide the food needed to produce shoot tissue for future photosynthesis. If turf is mowed too low in one event, an imbalance occurs between the remaining vegetative tissue and the root system, resulting in more roots being present than the plant needs physiologically. As a result, the plants will slough off the unneeded roots. Root growth is least affected when no more than 30 to 40 percent of leaf area is removed in a single mowing. Failure to mow properly will result in weakened turf with poor density and quality.
Cultural practices are an important part of golf course turf management, working hand-in-hand as part of IPM, water and irrigation management, plus golf course playability.
Best Management Practices
Maintain turfgrass mowing heights within the ranges of adaptation for the species and cultivars being grown.
Mowing frequency should increase during periods of rapid growth and decrease during dry, stressful periods.
If turf becomes too tall, it should not be mowed down to the desired height all at once. Such severe scalping reduces turf density and can result in a dramatic reduction in root growth. Tall grass should be mowed frequently and height gradually decreased until desired height of cut is achieved.
Shade affects turfgrass growth by filtering out photo-synthetically active radiation. As a result, turfgrass plants respond by growing upright in an effort to capture more light to meet their photosynthetic needs. As a result, mowing height should be increased by at least 30% to improve the health of turf grown in a shaded environment.
The use of the plant growth regulators has been shown to improve overall turf health when used as a regular management tool for grasses growing in shaded environments.
Environmental stresses such as prolonged cloudy weather or drought can have a significant impact on turf health. Increase mowing heights as much as use will allow in order to increase photosynthetic capacity and rooting depth of plants.
Use proper mowing equipment.
Reel mowers are ideally suited for maintaining turfgrass stands that require a height of cut below 1.5 inches. They produce the best quality when compared to other types of mowers.
Rotary mowers, when sharp and properly adjusted, deliver acceptable cutting quality for turf that is to be cut above 1 inch in height. They are more versatile on uneven terrain compared to reel mowers. Dull blades will result in shredding of leaf tissue, increasing water loss and the potential for disease development.
Flail mowers are most often used to maintain utility turf areas that are mowed infrequently and do not have a high aesthetic requirement.
Mowing patterns influence both the aesthetic and functional characteristics of a turf surface.
Turfgrass clippings are a source of nutrients, containing 2% to 4% nitrogen on a dry-weight basis, as well as significant amounts of phosphorus and potassium.
Nutrients contained in clippings can be sources of pollution and should be handled properly.
Clippings should be returned to the site during the mowing process unless the presence of grass clippings will have a detrimental impact on play. Cases when clippings should be removed include times when the amount of clippings is so large that it could smother the underlying grass or on golf greens where clippings might affect ball roll.
Collected clippings should be disposed of properly to prevent undesirable odors near play areas and to prevent fire hazards. Consider composting clippings or dispersing them evenly in natural areas where they can decompose naturally without accumulating in piles.
Alternate between mowing, rolling, and mowing when turf shows signs of stress.
Do not dispose of compost clippings near ponds, streams, or on impervious surfaces.
Remove clippings during periods of weed seed production, to reduce disease spread, to eliminate potential smothering of turfgrass plants from excessive clipping volume, or when clippings interfere with functional use of turf.
Cultivation
Turfgrasses are unique in three ways: they tolerate frequent close mowing; they persist under traffic conditions; and they form a dense, contiguous community. These characteristics make turfgrasses ideal for functional outdoor spaces like golf courses. However, high traffic areas such as fairways, tees, and putting greens can deteriorate with routine use.
The negative impacts of soil compaction and high wear will be evident in concentrated traffic areas. Thatch accumulation can be problematic in less trafficked areas. The surface of the soil profile (top three inches) needs to be actively managed to enhance turfgrass health by improving water movement, increasing atmospheric gas exchange, reducing root penetration resistance, and removing thatch accumulation. Accumulation of excessive thatch and organic matter will reduce root growth, reduce water infiltration, cause scalping, create an undesirable playing surface, and encourage disease and insect activity.
Cultivation involves disturbing the soil or thatch through the use of various implements to achieve important agronomic goals that include relief of soil compaction, thatch/organic matter reduction, and improved water and air exchange. Cultivation techniques will result in disturbance of the playing surface that can require significant time for recovery. Frequency of cultivation should be based on traffic intensity and level of soil compaction.
Core aerification is effective at managing soil compaction and aiding in improvement of soil drainage. Light and frequent applications of sand will smooth the playing surface, control thatch, and potentially change the physical characteristics of the underlying soil when done in conjunction with core aerification.
Best Management Practices
Core aerification involves removal of small cores or plugs from the soil profile. Cores are usually 0.25 to 0.75 inch in diameter. Annual core aerification programs should be designed to remove 15%-20% of the surface area. Use ISTRC to determine specific needs. http://www.istrc.com/ High-traffic areas may require a minimum of two to four core aerifications annually.
Core aerification should be conducted only when grasses are actively growing to aid in quick recovery of surface density.
Vary depth of aerification events by incorporating varying length tines to prevent development of compacted layers in the soil profile as a result of cultivation.
Solid tines cause less disturbance to the turf surface and can be used to temporarily reduce compaction and soften surface hardness during months when the growth rate of grasses has been reduced. Benefits are temporary because no soil is removed from the profile.
Deep-drill aerification creates deep holes in the soil profile through use of drill bits. Soil is brought to the surface and distributed into the canopy. Holes can be backfilled with new root-zone materials if a drill-and-fill machine is used. These machines allow replacement of heavier soils with sand or other materials in an effort to improve water infiltration into the soil profile.
Slicing and spiking reduce surface compaction and promote water infiltration with minimal surface damage.
Slicing is faster than core aerification but less effective. It is best accomplished on moist soils.
A spiker breaks up crusts on the soil surface, disrupt algae layers, and improve water infiltration.
Vertical mowing (verticutting) can achieve a number of different goals. The grain of a putting green can be reduced by setting a verticutter to a depth that just nicks the surface of the turf. Deeper penetration of knives will stimulate new growth by cutting through stolons and rhizomes while removing accumulated thatch.
Verticutting depth for thatch removal should reach the bottom of the thatch layer and extend into the surface of the soil beneath the thatch.
Dethatching with a verticutter is an aggressive practice that is not recommended on golf putting greens because of the damage that occurs and the extensive recovery time required.
Initiate vertical mowing when thatch level reaches 0.25 to 0.5 inch in depth. Shallow vertical mowing should be completed at least monthly on putting greens to prevent excessive thatch accumulation.
Groomers, or miniature vertical mowers attached to the front of reels, are effective at improving management of grain and improving plant density through cutting of stolons.
Top-dress the playing surface with sand following core aerification and heavy vertical mowing to aid in recovery of turf. Rates will vary from 0.125 to 0.25 inch in depth and will depend on the capacity of the turf canopy to absorb the material without burying the plants.
Light, frequent applications of topdressing sand on putting greens can smooth out minor surface irregularities, aiding in the management of thatch accumulation.
Use weed-free topdressing materials with a particle size similar to the underlying root zone.
Use of finer materials can result in layering and can have a negative impact on water infiltration.
Daily rolling of putting surfaces following mowing can increase putting speeds by roughly 10%, allowing for improved ball roll without lowering height of cut.
To minimize potential for compaction caused by rolling, use light weight rollers.
Topdressing
The goal of topdressing is to keep the crown of the turfgrass plant as close to the soil surface as possible by physically removing organic matter and thatch through cultivation and adding desirable rootzone material to the surface by sand topdressing. Obtaining this goal through proper management enables the turfgrass plant to maximize root development, minimize any disruption in water or air movement, and minimize pest pressure (disease/insect).
The particle size of topdressing material must be compatible with the existing rootzone material and topdressing materials should have the same particle size distribution as the construction mix or be coarser in texture. Topdressing materials finer in texture than the original construction sand can negatively impact rootzone infiltration rates and result in excessive moisture retention in the topdressing layer. Soil modification with sand of the top three inches results in higher infiltration rates and reduced runoff.
Best Management Practices
Apply higher rates of topdressing to putting greens in the spring and fall in conjunction with more aggressive forms of cultivation, harvest cores and fill holes with topdressing (Carrow, 2003). Apply lighter, more frequent sand applications (every seven to 14 days) throughout the growing season; or match sand applications with plant growth potential.
Laboratory test prospective topdressing materials using ASTM F1632, also known as the Standard Test Method for Particle Size Analysis and Sand Shape Grading of Golf Course Putting Green and Sport Field Rootzone Mixes. Compare the results to USGA guidelines for particle size distribution to determine the suitability as potential topdressing materials.
Laboratory test prospective topdressing materials using ASTM F1815, also known as the Standard Test Methods for Saturated Hydraulic Conductivity, Water Retention, Porosity, and Bulk Density of Putting Green and Sports Turf Rootzones, to ensure they meet USGA guidelines for hydraulic conductivity.
Sample existing greens on the golf course (15 to 20 subsamples at 4-inch depth or to the current topdressing layer depth if previously top-dressed) and laboratory test using ASTM F1632, and compare with the results with prospective topdressing materials to ensure compatibility.
Accredited labs such as:
International Sports Turf Research Center
Turf & Soil Diagnostics
Factors such as particle size, shape, color, uniformity and crusting potential, are all factors that contribute to creating aesthetics and playability.
Bunkers
In the rules of golf, a bunker is defined as a hazard consisting of a prepared area of ground, often a hollow, from which turf or soil has been removed and replaced with sand or the like. Bunkers are an integral part of nearly all golf courses and can be said to represent the personality of a course. Architects include bunkers in the design to provide aesthetic appeal and strategy by indicating the line of play.
Bunkers are defined as a hazard and provide some degree of difficulty to hit the ball out. The playability and management of bunkers is designed by the golf course architect and can vary greatly depending on the wishes of owners and skill levels of the intended golfers. They can result in an expensive item on the golf course, sometimes requiring more labor and expense to maintain than putting greens.
Three of the most important elements in constructing bunkers are drainage, liner, and sand selection. The drainage installed on the bunker floor will determine the level of moisture and firmness of the sand depending on how extensive the drainage system is and how quickly moisture leaves the bunker floor. The liner installed on the base of the bunker is of great importance in helping to avoid contamination of the sand and the reduction of sand washing down bunker banks during heavy rainfall. There are somewhere between six to 10 liners to choose from, each with a different methodology and particular materials. Most will do an excellent job.
The selection of sand is important because this item has the most influence on playability. Conducting a sand analysis with an accredited lab is recommended. The most important factor to evaluate may be the penetrometer reading, which will give a good prediction of the tendency of a sand to result in “fried egg “ lies. Generally, a penetrometer reading above 2.20 will result in a sand with a low potential for the ball to bury. The infiltration rate is another parameter that is important in determining a favorable bunker sand. A minimum rate of 30 inches per hour is suggested. It is difficult to predict how a bunker sand will actually play, so it is recommended that a golf course acquire a few potential sands and create test bunkers for golf pros, committee members, and other interested players to trial before making a decision. Visits to other golf courses is another way to test out various bunkers’ sands.
Sand depth and weather are important parameters in the final playability of a bunker sand. The USGA recommends an average sand depth of 4 to 6 inches at the base of the bunker and 2 to 3 inches on the faces. Finally, the maintenance of bunkers will ultimately create the playability of the surface.
Bunkers can be raked in two ways, either with a motorized bunker rake or by hand raking. Smaller bunkers must be raked by hand, while larger ones lend themselves to the labor-saving motorized units. Many different types of rakes and methodologies are used to create a smooth surface for the best playability. One of the most economical methods of raking is the “Aussie” method which involves only raking the base of the bunker, leaving the banks untouched to firm up and allow the balls to run down into the middle.
Frequent rainfall or irrigation and shallow raking will end in firm bunker surfaces, while dry weather and deep raking tend to create a soft surface. Golfer preference for bunker playability is a very personal thing with many players preferring a soft surface while others enjoy very firm sand.
Best Management Practices
Consider maintenance costs and golfer clientele when designing bunkers. High flashed faces, numerous capes or intricate edges, revetted, and greater numbers of bunkers will increase difficulty and drive up costs.
When constructing bunkers include extensive herringbone drainage and a well-researched bunker liner.
Contour bunker surrounds so that they do not drain surface water into the bunker resulting in washouts.
Irrigation should be installed that will water the bunker banks as well as the sand to keep it from becoming too dry.
Create test bunkers to help select a new sand.
Use an accredited lab to test bunker sands to help in making a good sand selection.
For best playability, install bunker sand depth with 4 – 6” of sand on the bunker floor and 2 -3” of sand on banks.
Strive to maintain a weed-free, smooth sand with a minimum potential for “fried egg” lies along with firm bunker banks.
Rake bunkers 4x per week to help maintain a consistent surface, touch them up on other days to save labor.
Mow bunker banks weekly with edging completed on a 2 to 4-week interval.
Probe sand to maintain proper depths every two weeks or so depending on whether bunkers are flat or highly contoured.
To keep bunkers looking their best, when they begin to look dirty and contaminated, remove the top 1-2” of sand and replace it with new sand.
When bunkers get too firm, use a motorized bunker rake with cultivating tines to fluff up the sand and improve playability.
Golf course architects recommend rebuilding bunkers on a 7-year interval; this timetable can change depending on the speed of bunker degradation
Shade and Tree Management
In general, most turfgrasses perform best in full sun. Excessive shade reduces photosynthesis and air circulation, thus increasing the susceptibility of the turf to pest and disease problems. It is important to maintain healthy trees and prune as needed.
Best Management Practices
Prune tree limbs and roots as needed to reduce competition for sunlight, water, and nutrients.
When possible, trees located near closely mowed areas such as tees and greens should be removed or relocated, or their canopy should be thinned to promote good turf growth.
Understand the variability in sun angles at different times of the year and how this affects turf health.
Conduct a shade audit to identify problem areas. Use apps like “Sun Seeker” to identify the trees causing shade.
Working with an arborist, conduct a tree survey that identifies each tree’s location, species, health, life expectancy, safety concerns, value and special maintenance requirements.
