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Minimizing Turf Damage From Hydraulic Oil Leaks

USGA Green Section | Published on 10/2/2024
By: John Petrovsky, manager, Green Section Education


Hydraulic oil leaks are an unfortunate reality that superintendents have to deal with. Is there anything that can be done to reduce the risks, minimize damage and speed up recovery? Research has some answers, but you may not like them.

Key Takeaways

  • It is the hydraulic oil itself that damages turfgrass, not the temperature of the oil. Research shows that hydraulic oil will kill grass whether it is hot or at ambient temperature.

  • Vegetable-based, synthetic and petroleum-based oils all significantly damage turfgrass. However, synthetic oils cause less injury under certain conditions than other types of hydraulic oil and recovery is faster.

  • Hydraulic oil readily moves through the turf canopy into the soil, spreading downward and laterally. It negatively affects soil health and can persist for a long period of time.

  • Flushing with water or applying various products has not been shown to reduce damage or speed up recovery.

  • Removing and replacing damaged sod and contaminated soil is a labor-intensive but effective method of remediation.

  • Electric mowers eliminate the risk of hydraulic oil leaks. With conventional equipment, preventative maintenance is the best way to avoid leaks and proper training of employees can reduce damage if a leak occurs.


     

Golf course superintendents dread hearing that a piece of equipment had a hydraulic oil leak on the course – especially on greens, tees or fairways. Thoughts of dead grass, figuring out how to deal with it, and explaining to golfers what happened can swirl as the superintendent drives out to the scene of the crime. If a leak happens in the dark or the operator isn’t paying close attention, multiple holes can be affected. Is there anything that can be done to minimize the damage and speed up recovery? Should you immediately start hand watering the area with wetting agent pellets or dishwashing soap? Do you have to remove the soil, or can you just cut out the dead strips of grass and resod? What would happen if you didn’t do anything?

When it comes to managing hydraulic leaks, there’s a lot of misinformation out there that can cause superintendents to respond in a way that doesn’t help or sometimes makes the damage worse. In this article, we look at what the research says you should do and get to the bottom of what actually kills the grass, the fate of the oil and other important considerations.

Why Does Hydraulic Oil Kill Grass? Spoiler Alert, It’s Not the Heat.

Anyone who has been in the golf maintenance industry for a while has likely heard someone say: “It’s the heat that kills the grass, not the oil.” The notion that the high temperature of the oil is as much a cause of injury as the oil coating the plants and moving into the soil appears often in social media posts, trade publications and is even alluded to in some of the earlier scientific literature. This seems plausible, but the research shows that this is not the case.

The late Dr. William “Lee” Berndt was a leading expert on hydraulic oil leaks in turf and studied all aspects of the issue during his long and accomplished scientific career. Having heard this claim repeatedly, but not finding any supporting research to back it up, Dr. Berndt decided to initiate a series of experiments to investigate.

In a study conducted in 2005 and 2006 on hybrid bermudagrass and seashore paspalum, Berndt found that increasing the temperature of hydraulic oil from 122 degrees F to 176 F had no impact on the amount of turf that died or how long it took to recover (Berndt, 2007). Another experiment in 2014 on ‘TifEagle’ bermudagrass, looked at the effects of applying hydraulic oil at 95 F (air temperature) and at 176 F (oil at maximum operating temperature in a mower). After one week, there was no difference in the amount of dead bermudagrass between the two treatments, confirming the results of the earlier study (Berndt, 2018).

One interesting finding from the 2014 study was that hot water (176 F) also killed bermudagrass shoots. In reality, any very hot fluid can injure or kill turfgrass. The difference with hydraulic oil is that it will kill turfgrass regardless of the temperature. No matter if the hydraulic oil was hot or cool, all grass exposed to it was just as dead a week later. It also continues to kill turf as it moves in the canopy and soil, which was a topic of additional research studies.
 

"No matter if the hydraulic oil was hot or cool, all grass exposed to it was just as dead a week later."

Hydraulic Oil in the Soil

Hydraulic oil is a petroleum-based fluid made of hydrocarbons, which are widely known to be toxic to plant life. Hydraulic oils are also hydrophobic, coating soil particles and making them water-repellent while increasing a soil’s carbon-to-nitrogen ratio, which negatively impacts plant health further (Everett, 1979).

As part of the previously mentioned study on the effects of oil temperature, its movement in the soil and effect on plant health were also investigated in a separate greenhouse container study. Movement of a vegetable-based oil, synthetic oil and a conventional petroleum-based oil into the soil was found to be mostly via capillary action and gravity, typically leading to a “plume” effect as the oil spread downward and laterally. Just one-tenth of an ounce of hydraulic oil seeped down 1.5 inches and affected 6 cubic inches of soil (Berndt, 2007). Interestingly, the synthetic hydraulic oil resulted in significantly less damage to hybrid bermudagrass, both above and below ground, which is discussed next.

Are Vegetable Oil-Based or Synthetic Fluids Safer Than Petroleum-Based Oil?

Vegetable-based hydraulic oils have been promoted as a biodegradable solution to the hydraulic oil leak problem and some early research found them to be less harmful to turfgrass in long-term trials (up to a year) following a leak (Elliott & Prevatte, 1995). However, more-recent research has shown that not to be the case.

In the 2007 study alluded to earlier, researchers investigated the difference in turf damage from three different hydraulic oil types: conventional petroleum-based oil, biodegradable vegetable-based oil and a synthetic poly-glycol-based oil. In a container study, pots were treated with each of the oils and assessed for tissue and root damage over time. Results showed that the poly-glycol-based synthetic hydraulic fluid caused substantially less turf injury and preserved a greater degree of rooting than either vegetable-based hydraulic oil or petroleum-based hydraulic oil when spilled onto ‘TifEagle’ bermudagrass turf (Berndt, 2007). Unlike the 1995 study, vegetable-based biodegradable oil did not lessen injury.

A separate field study on bermudagrass and seashore paspalum putting greens was conducted as part of this experiment and also demonstrated poly-glycol-based synthetic hydraulic fluid caused substantially less turf injury than the vegetable- or petroleum-based oil. The petroleum-based oil resulted in more damage than the vegetable-based oil. Interestingly, ‘Tifdwarf’ bermudagrass was damaged less than ‘TifEagle’ and seashore paspalum was impacted the least (Berndt, 2007).

 

Poly-glycol-based synthetic hydraulic oil (Syn) caused less injury to this bermudagrass putting green than vegetable-based oil (Veg) or mineral-based oil (Min). Multiple studies have found this specific type of synthetic oil reduces injury in certain situations and can be flushed through the rootzone. (Dr. William Berndt)

In a 2014 study, scientists again compared the damage caused by a petroleum-based oil, a vegetable-based oil and a synthetic oil. Again, synthetic oil reduced the extent of turfgrass damage compared to petroleum and vegetable oils. Researchers hypothesize this is due to differences in properties like viscosity and density, which can affect the persistence and dispersion of hydraulic oil in the rootzone (Berndt et al., 2017).

So far, all the research discussed has been on warm-season grasses. A study conducted at Penn State University from 2010 to 2012 had the goal of evaluating hydraulic oil leaks on cool-season turf. In their study comparing five different types of hydraulic oils (one petroleum, one vegetable, two synthetic and one diester) they found all hydraulic oil treatments killed ‘A-4’ creeping bentgrass within two weeks (Kaminski et al., 2019). However, another question this study sought to answer was how remediation practices can mitigate damage. They came to a similar conclusion as Berndt did, that synthetic polyalkylene glycol hydraulic fluid causes less damage to turf, but only if certain remediation practices are performed after a leak.

What Should You Do After a Leak?

Theories about how to respond to a leak are wide-ranging and full of misinformation. When a post appears on social media from an anxious turf manager looking for advice following a hydraulic leak, the solutions offered can run the gamut. Researchers looked at some common remedies to see if any make a difference.

Flushing with water and/or detergents

Drenching the leak with water hoping to flush the oil through the soil is one of the most common responses. Unfortunately, studies show that this approach does not reduce damage or shorten recovery time (Berndt et al., 2017; Kaminski et al., 2019). Adding detergent to a water flush is sometimes espoused as a remedy, but that has been shown to actually increase the extent of injury by dispersing the oil further (Berndt, 2018). The only exception to this was with synthetic oil, specifically polyalkylene glycol fluids. Penn State’s research indicates applying a detergent and water solution to this type of hydraulic oil leak, brushing it in and then rinsing, eliminated turfgrass injury after four weeks. It’s important to note this detergent, brushing and rinsing remedy did not work on petroleum- or vegetable-based hydraulic oils.

Other remedies

Other products often used in an effort to mitigate damage or speed up recovery include wetting agents and other surfactants, activated charcoal, clay materials, kitty litter, saponifiers, emulsifiers and organic amendment products. Cultural practices including aeration and topdressing, scalping the turf and verticutting are sometimes promoted as ways to speed up recovery as well. There is no research that shows any of these approaches consistently mitigate damage or speed up recovery.

The fastest way to recovery

The oil causes the damage, and until it’s gone recovery will be slow. How slow depends on factors like soil type, time of year, plant species, overall plant health and your climate. For example, damage from a hydraulic oil leak on a perennial ryegrass/Kentucky bluegrass tee in New Jersey in November will likely be visible until the following spring if recovery is left to Mother Nature.

Although it’s labor-intensive and time-consuming, stripping the damaged sod, removing and replacing the contaminated soil, and sodding the area with new grass is probably the fastest way to repair hydraulic oil leak damage. A hexagon turf repair tool or other type of plugger can be used to repair damage from smaller leaks. Be sure to dispose of the contaminated sod, soil or plugs in the same way you would any other oil-soaked material.


 

Removing and replacing contaminated turf and soil is labor-intensive and time-consuming, but it’s the fastest way to repair damage from a hydraulic oil leak.



A (Fluid) Ounce of Prevention

Hydraulic features on golf course mowers became popular in the 1960s, thanks to machines like the Toro Parkmaster, and have long been the standard for larger mowers in the golf maintenance industry. Fortunately, today’s mowers are much less prone to hydraulic leaks thanks to better engineering and materials. Still, it’s important for golf course superintendents to work with equipment technicians to minimize the chance of leaks. The last thing you want is to have a hydraulic hose blow that you already knew was in bad shape.

It's also vital to train operators on how to detect hydraulic leaks as soon as possible and how to react. It’s common to see photos of hydraulic leaks with lines of fluid on every pass across a green. Mowing often takes place in the dark so it can be difficult to spot a leak. However, operators should always be alert for any sudden change in noise from the reels or hydraulic pump, sluggish response when steering, or units lifting abnormally. Glancing at the previous pass occasionally can also tip off an operator to an issue. If a leak is detected, it’s critical to move the machine off the turf immediately – preferably onto an impermeable surface away from drains or water features to minimize any environmental impact and make cleanup easier.


 

Damage like this may be avoidable by training operators how to detect signs of a hydraulic issue and how to react.

There Is No Quick and Easy Fix

Since the introduction of hydraulic components in golf course maintenance equipment, there have been hydraulic oil leaks and superintendents have tried just about everything to mitigate damage and speed up recovery. Researchers have studied many popular products and tactics used to respond to hydraulic oil leaks and found that none of them work well on a consistent basis. Using electric mowers is one way to avoid hydraulic leaks, but this type of equipment is still not widely used in the golf course maintenance industry.

For the foreseeable future, hydraulic oil leaks will be a significant risk for turf managers and more research is needed to find products and methods that can minimize the damage. For now, keeping hoses and other components of the hydraulic system in good shape and training staff to be vigilant while mowing are the best ways to avoid losing turf due to a leak.

This article is dedicated to the memory of William “Lee” Berndt, Ph.D., who sadly passed away in 2024. Dr. Berndt’s contributions to turfgrass science were great and he will be missed.

References

Berndt, W.L. (2007). Effect of synthetic hydraulic fluid on warm-season turfgrass. Applied Turfgrass Science, 4, 1-13. https://doi.org/10.1094/ATS-2007-1119-01-RS

Berndt, W.L., Riger, J.W. & Riger, C.W. (2017). Nonlinear regression modeling of hydraulic oil injury on a bermudagrass green. International Turfgrass Society Research Journal, 13, 240-249. https://doi.org/10.2134/itsrj2016.04.0216

Berndt, L. (2018). Does temperature influence hydraulic oil injury? Golfdom, 74(1), 47.

Elliott, M. L., & Prevatte, M. (1995). Comparison of damage to 'Tifgreen' bermudagrass by petroleum and vegetable oil hydraulic fluids. HortTechnology, 5, 50-51.

Everett, K. R. (1978). Some effects of oil on the physical and chemical characteristics of wet tundra soils. Arctic, 260-276.

Kaminski, J. E., Lulis, T. T., & Russell, T. R. (2019). Hydraulic fluid type and remediation practices on hydraulic leak injury to creeping bentgrass putting greens. HortTechnology, 29(6), 941-945. https://doi.org/10.21273/HORTTECH04447-19


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