After the Spill
The advent of the triplex greens mower has been a great benefit for golf courses. These machines allow courses with limited labor to maintain good playing conditions without hand-mowing. Even courses that regularly mow greens by hand can turn to triplex mowers on the weekends when time counts more than usual.
Unfortunately, the benefits of triplex mowers come with a price: the potential for hydraulic leaks. Not only triplex mowers, but tractors, aerators with hydraulic lift cylinders and any other machine that relies on hydraulics can significantly damage turf if a hydraulic leak occurs.
Most hydraulic fluids will kill putting-green turf. Even those that claim to be more environmentally benign are still damaging because the high temperature of the fluid (160 to 200°F) is enough to kill the grass.
I suppose you could call it the Murphy's Law of putting greens: Hydraulic hoses always seem to break when and where the damage is least tolerable … greens closest to the clubhouse, just prior to a major event or on an already-stressed green that can withstand no additional hardship. Of course, there really is no good time or place for a leak. Hydraulic leaks result in significant turf loss and a reduction in putting-green playability — things you never want to see.
Little research has been conducted on turf to assess recovery from machine-fluid damage; even less on turf maintained at putting-green height. However, practical field observations, combined with the small amount of research that is available, suggest some useful tactics to deal with hydraulic leaks.
BEFORE THE LEAK
Are hydraulic leaks preventable? Yes, but not entirely. As mowers age, you should check hoses regularly for any signs of wear and replace them, if necessary. Unfortunately, even brand new hoses can spring a leak (this is personal experience talking) resulting in turf loss. So, you can take preventative measures, but they are not foolproof. If you use triplex mowers or rollers on your putting greens, it is not a matter of if you will experience damage from a hydraulic leak; it is a question of when. The key to addressing the damage is to have a procedure in place to quickly fix any hydraulic mishap that occurs.
AFTER THE LEAK
Certain measures can improve turf's recovery if you implement them immediately after a leak occurs. For example, dishwashing liquid will disperse the hydraulic oil. While this may reduce the severity of the damage, it also can spread the problem over a slightly larger area.
Activated charcoal can also be used to absorb the oil, but its benefits are minimal. Activated charcoal also is messy to apply.
Some biological materials that claim to reduce the damage caused by petroleum products have come into the marketplace. Independent research on their effectiveness is limited, but they are one avenue that superintendents can explore and judge for themselves.
Any of these techniques may help to reduce the severity of damage, especially on higher-cut turf. However, on putting greens, playability dictates quick repair for which the above-mentioned techniques may be of little value.
You'll need to consider different factors before jumping into the repair process. The most important question is, “How bad is it?” A major hydraulic leak will require sodding or plugging, while a smaller leak may be left to heal on its own.
The second question is, “Where is the damage?” If damage from a hydraulic leak occurs in an area that is generally not in play, the need for repair may not be urgent. However, if it occurs in the middle of a green and it impacts many usable hole locations, repair will need to be immediate.
Sodding or plugging can repair the turf quickly and return the affected area to play as soon as possible. Without sodding, a hydraulic leak on a creeping bentgrass or bentgrass/Poa annua green will take 4 to 6 weeks to heal. On bermudagrass, healing actually may be more rapid without sodding. However, playability will still be affected for a long period.
Sodding addresses concerns about soil residual of hydraulic fluid. However, research at the University of Nebraska indicated that oil residual did not impact seed germination and survival when areas were repaired from seed.
When making a sod repair, remove and replace one narrow strip of sod at a time so that you do not alter the putting green's contours. The goal is to finish the job with as little change to the putting green as possible.
The final option for repair is to overseed and topdress the affected area to promote healing. As I mentioned, seed germination was not impacted by oil residual in a study that looked at this issue. The biggest problem with this approach is the downtime that it requires. However, small or out-of-play areas easily can be addressed in this manner. Be sure to provide enough surface disruption through spiking or aeration to create good seed-to-soil contact. Otherwise, seed germination will be significantly slower.
THE NURSERY GREEN — YOUR INSURANCE POLICY
For any significant damage that occurs on a putting green, a nursery green can be a perfect insurance policy. A putting-green sod nursery offers the opportunity to match turfgrass compositions, soil type and maintenance practices with the damaged greens. Areas repaired with sod from an on-course nursery will blend in quickly and soil compatibility problems will be minimal. Sod from outside sources can pose significant problems, especially with blending the sod with the existing turf. This is less of a problem where greens are composed of pure creeping bentgrass. However, pure creeping bentgrass sod does not blend well in a bentgrass/Poa annua green. For bermudagrass, it's easier to be relatively sure that the sod being used to repair damage is the same as that established on the greens.
HEALING THE DAMAGE
Once you actually make the repairs, do not forget to increase nitrogen fertilizer inputs in the repaired areas to promote more rapid healing. Field experience shows that foliar applications with urea or ammonium sulfate at 0.1 to 0.125 pound of nitrogen per 1,000 square feet on a 7- to 10-day interval can speed healing. Where you use sod or plugs, frequent, light topdressing will help to smooth the affected areas. Do not forget to hand-water sodded areas to prevent desiccation during hot weather. Sodded areas may need to be watered two or three times daily depending on weather conditions. Once you make repairs, focus maintenance efforts on the affected areas to maximize the rate of healing.
WHAT KIND AND HOW MUCH?
For many years, biodegradable crop-based oils have been available for use as hydraulic fluid for golf-course equipment. One question raised is whether these crop oils reduce damage from hydraulic leaks. The answer is, “No.” Initial damage from petroleum-based oils and crop oils are similar because it's the temperature of the oil when it contacts the turf that causes damage. Therefore, severity of damage relates more to the volume of oil spilled rather than the type of oil.
For recovery, however, there are differences among oil types. For major leaks where sod or plugs are needed for repair, there appears to be little advantage to crop-based oils. However, if greens are left to heal on their own, the Nebraska research indicated that areas affected by crop-based oils recovered more quickly than petroleum-based oil spills. This could provide a significant advantage on fairway turf where immediate repair is less necessary.
Any machine using hydraulics holds the potential to cause significant turf damage if a leak occurs. Most superintendents have to contend with this type of damage on greens at some point in their careers. For major damage, the only option for rapid healing is to remove the damaged turf and replace it with sod or turf plugs. A putting-green nursery can make such repairs easy to implement. With patience, hydraulic leaks will heal on their own, but playability and appearance of affected areas will last for several weeks or more.
Darin S. Bevard is the Mid-Atlantic regional agronomist for the U.S.G.A. Green Section. He is based in Kennett Square, Pa.
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