A SHARP IDEA

by CHRISTOPHER E. HARTWIGER

Sometimes new challenges can be overcome with old solutions. The advent of high-density bentgrass and bermudagrass varieties is raising the level of putting quality on putting greens throughout the country. However there is a price to be paid to meet this higher standard because many of these varieties require a more intensive maintenance program.

Paul Jett and Jeff Hill at Pinehurst Resort and C.C. (Pinehurst, N.C.) have found dethatching to be an extremely important part of the management program for the G-2 bentgrass greens on Courses #2 and #8. The G-2 bentgrass has an extremely fine texture and requires exceptionally low mowing for optimum playability. They have concerns about rapid accumulation of organic matter in the upper portion of the profile as well as the incorporation of sand topdressing into the canopy. They have found that routine dethatching of the greens successfully addresses both of these concerns.

EVOLUTION OF A SAND-BASED PUTTING GREEN
From the moment that grass is established on a sand-based putting green, the physical properties of the soil in the upper portion of the profile begins to change. Organic matter in the form of old roots and other plant matter accumulates, which can alter the balance of pore space. Typically, more capillary pore space is created at the expense of larger macropores. Since the capillary pore space contains water virtually all the time, soil oxygen and infiltration rates decrease.

Managing the physical properties of the soil in the upper portion of the profile is essential to maintaining healthy bentgrass through the summer months. Physical removal of accumulated organic matter and the incorporation of topdressing are the two primary means of accomplishing this goal. These practices are even more vital in managing the new high-density bentgrass and bermudagrass varieties.

THE DETHATCHING PROCESS AT PINEHURST
At Pinehurst, Mr. Hill and Mr. Jett use the Graden Vertical Mower to dethatch the G2 bentgrass greens on Course #2 and Course #8 every six to eight weeks. A deeper setting is used for organic matter removal and a shallower setting is used to create channels for topdressing incorporation. The unit is gentle on the turf and complete recovery occurs within a week, regardless of the depth used. Mr Hill and Mr Jett believe aggressive dethatching removes more organic matter than core aerification, with less recovery time.

Light, frequent topdressings are essential to help maintain good porosity, firmness, and dilute the accumulation of organic matter. However sometimes the turf canopy on some of these varieties is so dense that the larger particles are not readily incorporated. If the mowers are removing the larger sand particles, the benefits associated with light topdressings are not realised. Mr Jett and Mr Hill have found a light dethatching can be used to open up the canopy for easier incorporation of sand topdressing.

The cleanup process requires two easy steps. First, snow shovels are used to push the removed material to the edge of the green for easy pickup. Next, crew members with backpack blowers blow any remaining material off the greens. After rolling and/or mowing the next day, the greens are back in play with minimal disruption.

USING THIS TIP AT YOUR GOLF COURSE
The physical removal of organic matter and frequent topdressings are more important than ever before when managing a new high-density bentgrass or bermudagrass variety. While some organic matter is essential to provide wear tolerance, too much will place the greens at risk for problems during periods of high heat and humidity. Paul Jett and Jeff Hill have found dethatching to be a major key in addressing this concern and a means to help provide players with outstanding conditions throughout the year. However, dethatching is a process that can be beneficial to older golf courses with sand-based putting greens. This practice can help remediate situations where the excessive accumulation of organic matter is hindering the performance of the greens.

The first step in implementing a dethatching program is acquiring a piece of equipment that can handle the job. Ideally, select a unit that can cut two inches deep into the profile without any difficulty or major disruption to the canopy. Generally, verticutting reels on triplex mowers are not an option because they will not cut deep enough into the profile.

The next step is to set a dethatching schedule that is appropriate for your golf course. Keep in mind that optimum times for dethatching bentgrass and bermudagrass greens will vary. Identify whether your objective is to assist in the incorporation of topdressing or organic matter removal. Aggressive dethatching should be performed during the period of peak growth to avoid stress and minimise the recovery period of the turf. A shallower setting is more desirable for the incorporation of sand topdressing.

Golfers' expectations and superintendents' skills continue to raise the standards of putting quality. Using this sharp idea at your golf course will benefit the greens automatically and will give you a head start in meeting those rising expectations.

CHRISTOPHER E. HARTWIGER uses his well-honed skill as an agronomist in the Southeast and Florida Regions. He makes Turf Advisory Service visits in Tennessee, North Carolina, South Carolina, Georgia, Alabama, Mississippi and Florida.

Note:
1. Pinehurst Resort and C.C. is the site of the 1999 US OPEN. The Open will be played on the #2 Course.
2. Pinehurst has been operating 2 Graden GS04 Verticutters for approximately 18 months.
3. At the GCSAA Trade Show in Orlando in February Paul Jett was very enthusiastic about the GS04. He has one unit virtually for exclusive use on the #2 course. He told us at the show that he had invited superintendents from other major clubs to play on the course last September and all were impressed with the condition of the greens. This he put down to the use of the GS04. At least 4 of the 6 superintendents were able to persuade their clubs to purchase GS04s based on their experience at Pinehurst.