It has been proven since the inception that modified sand based greens and the USGA specification greens can not function properly with thatch accumulations of greater than 2% in the upper three inches of the rootzone. The superintendent’s duty is to mitigate these excess accumulations of thatch and organic material. This is accomplished by a carefully planned program to cultivate, remove and dilute the thatch and organic layer and restore the original design characteristics and the air and water movement specifications to the rootzone.
The program for thatch and organic matter management with sand based greens
Late Winter – Early Spring
This program deals mainly with fall cultivation; however success is due to a season-long management program. The ideal program begins in late winter to early spring with a greens aerification using 5/8-inch tines. Cores are removed; then straight sand topdressing matching the original mix is added to fill the aerification holes. At this time you may also add a laboratory recommended soil amendment to be added to or with the sand. Dictated by on soil tests, a program may call for additions of slow release mineral or organic fertilizer or other minerals needed by the rootzone to supply the turf with balanced recommended nutrients. This early-season heavy cultivation allows the greens to weather the stresses of June, July and August.
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| Aerification Hole Filled with Sand |
Throughout the Seasons
Once greens are healed from the initial work, you should begin a season-long verti-cutting and topdressing program at approximate three-week intervals, you should vigorously verticut in two directions then follow up with a light topdressing, applying the material in two or three directions with a spinner type spreader. Depending on rate of application, the top dressing is either brushed in or lightly watered. Greens should then be rolled mowed using backup units or just rolled; the golfer should experience virtually no disruption to the putting surface. Depending on weather, you should strive to maintain an aggressive verticutting/topdressing schedule during the spring and early summer. During the height of the summer, adjust this program as necessary and perhaps substitute with HyroJect applications because of weather extremes.
Late Summer
When late August arrives, you should begin the fall cultivation program. On the Monday and Tuesday before the Labor Day weekend, all greens are serviced with DryJect or HyroJect. These machines fracture the rootzone using water at high pressure. The DryJect creates an opening in the turf and then the machine injects a topdressing material into the hole. Light topdressing when using the HyroJect is recommended since sand is not injected with is brand of aerification machine. Since water is used in the process the greens should be allowed to dry. They are then brushed, mowed and opened for play. The advantage of using the DryJect is that a green of 5,000 to 6,000 square feet can be aerified, sand injected, cleaned and mowed in approximately 1/1/2 to 1 3/4 hours, Minimum disruption occurs with this process and greens are very playable after rolling and mowing.
Contracting these aerification processes out to a specialized contacting company make for a fast process. The companies generally use three or four machines. You would provide the topdressing material; with the addition of one laborer with each machine, your crew would also be responsible for the final cleanup and mowing. Two full days should be dedicated to this process.
It should be noted that DryJect and HyroJect is not a true aerification process, since no cores are removed and no organic matter management is achieved. The main objective in this initial step is to relieve some compaction, generate new root growth at the aerification site, develop a better gas exchange, help in water infiltration and incorporate fresh topdressing material into the green profile.
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| Toro HyroJect |
With reasonable growing conditions, the greens show no evidence of the DryJect or HyroJect service seven to 10 days after the procedure.
During this time it is also the ideal time to incorporate seed into the green surface as needed. There are many methods that can be used to accomplish this procedure. The Graden or deep Verti-Cutting will work well to prepare a seedbed. Bentgrass seed should be place no deeper than ½ inch with ¼ being the minimum. The seed should be placed with a drop-spreader and lightly dragged into grooves created by the slicing process. The recommended seeding rate for bentgrass seed is ¼ pound per 1000 ft². The seeded areas should be kept moist for at least ten to fourteen days to hasten germination.
Mid - Fall
Mid-October begins step two in this process. This consists of heavily dethatching all greens using a Graden dethatching unit from Australia. This unit can penetrate a turf surface to a depth of 1 1/2 inches. You should set spacing of the blades at 1 inch. Using the thicker 9/64- inch blade, the dethatching operation can impact slightly better than 14% of a greens surface area. An option available is to use a 5/64-inch blade, which then impacts nearly 8% of the surface. The intent is to aggressively manage the organic material profile in the mix so the thicker blade is the one that should be used.
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| Graden Vertical Mower |
An average green can be dethatched in less than an hour depending on its size. Cleanup takes longer since a considerable amount of material is generated. It’s best to use blowers to clean the surface. Once the green is cleaned, topdress it with sufficient material to fill these newly created grooves. The material is brushed or blown in, greens all mowed with back up units and you will again ready for play. An average size maintenance staff of six should complete nine holes of dethatching, cleanup and topdressing in a normal eight-hour workday.
Though not a traditional aerification, the heavy dethatching, can be is as effective as coring with less putting disruption, Using 1-inch tines on a spacing pattern of 1 inch by 2 inches will impact slightly more than 15% of the surface area, so deep dethatching work is comparable to pulling cores. The positive outcome to this operation is less putting disruption and more content golfers.
Depending on weather, healing takes from 10 days to two weeks. During that time a light spoon feeding of liquid fertilizer will be applied to aid in the recovery process.
It is paramount that organic material management is practiced throughout the year. A constant effort to keep organic matter in the 1 to 2 percent range is critical to plant health as well as playability. Organic matter percentage is measured by taking undisturbed core samples and sending them off to a lab for analysis not an inexpensive process, but one that needs to be performed if you wish to track the level and success of your management program.
Early - Winter
By early November a decision must be made whether to put the Graden on greens for dethatching in a second direction or to aerate using 1/4-inch tines. These 1/4-inch tines on a 2-inch by-2-inch spacing only impact slight more than 2% of the surface area, so the question becomes, is the impact significant enough to justify the effort? Usually we just go back with Gradens equipped with 5/64--inch blades. This operation impacts about 8% of the surface area. With two fall dethatching procedures combined, you will have impacted nearly 22 percent of the green surface area. Because firm greens and a removal of organic matter are the goals, this double dethatching should works well for most USGA or sand modified greens rootzones.
Mid - Winter
By December most play will be considerably low. At that time it would be advisable to apply snow mold materials for winter protection. A final heavy top dressing is then applied to all greens (between ⅛ and ¼ inch). After topdressing brush all greens so a uniform covering is achieved.
This late-season topdressing allows for winter protection, since snow cover may or may not be a normal occurrence in you part of the world. Also, after a few early-season mowings, the greens, although not yet quick, are quite smooth and true.
As important as golfer satisfaction is, the agronomic needs of the plant should also be considered. Because most of us manage USGA greens or sand modified rootzones, our major intent is to manage the organic matter portion in the rootzone (upper 3 inches). Compaction is a consideration, but not the major factor in how the program was developed. If you can achieve balance in fertilization, watering, cutting height and pest management programs then aggressively manage the organic matter in the top three inches, I feel confident your greens will perform much better.
I also feel comfortable that this approach to greens cultivation and organic matter management will be effective on older-style push-up greens. Most of these greens have been modified by years of topdressing so the profile is in many ways similar to that of a sand modified rootzone green.
Aerification a golf course is a balancing act between making strong agronomic improvements vs. politics and playability. As technology evolves, newer and different equipment will come to the marketplace, changing our approach to many facets of our profession. The modern superintendent will examine these changes to determine what portions best fit his or her programs. This constant experimentation and innovation give golfers the wonderful turf conditions they now enjoy. Continued experimentation and innovation will move our craft and the game of golf forward.
The strength of this program lies in its season-long approach. All of these operations, equipment and procedures play important roles in this cultivation philosophy. In severe thatch and organic matter percentages these programs may not substitute for deep core aeration, but I have found them to be very effective tools in an effort to produce top quality turf. They are less disruptive to play and a machine such as the Graden does remove a great amount of thatch. An integration of various approaches utilizing different machines makes this program successful.
In discussions with many superintendents, I often hear that attempting to balance the needs of the plant versus the needs of the golfer difficult work. The answer is that it cannot work easily. There will always be some golfer discomfort any time disruptive management practices are undertaken on a green. Only through continued member education will the process become more harmonious. The superintendent’s efforts should always be aimed at meeting the needs on both sides of the equation and, hopefully, getting all parties on the same page of the book.
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