Hydrocarbon machine fluid injury on greens: What do we know?

By |  March 26, 2018 1 Comments

Motorized turfgrass management equipment uses hydrocarbon-based machine fluids, including fuels, lubricants and hydraulic oils. Leaks of these machine fluids injure turf, especially on greens (Photo 1). The most pronounced visual symptom of machine-fluid injury is an area of turf exhibiting loss of visual green color with the onset of shoot necrosis.

Photo 1 The aftermath of a hydraulic oil spill on a TifEagle hybrid bermudagrass putting green in southwest Florida.

Over the last 35 years, only a handful of research reports have addressed machine-fluid injury. Gaining a better understanding of this injury type through additional research may lead to enhanced spill-mitigation tactics. This could be important for golf course superintendents, as spills of machine fluids occur frequently on greens all over the world. This article summarizes our current understanding of machine-fluid injury on putting green turf.

Machine fluids are contact phytotoxins

It’s not yet clear why machine fluids are phytotoxic. A literature review suggests petroleum hydrocarbons (i.e., gasoline) are lipid solvents, which upon contact with grass shoots causes dissolution of cell membranes. Rupturing of cell membranes causes cell constituents to leak out, resulting in cell death. Alternatively, other petroleum hydrocarbons (i.e., oil) may physically obstruct stomata, interfering with gas exchange and transpiration. Hydrocarbons infiltrating the root zone may cause anaerobic or hydrophobic root zone conditions that interfere with essential functions such as root respiration and the uptake of water/nutrients.

Spills affect shoots and roots

It’s obvious that machine fluid spills affect turfgrass shoots, as canopy injury is visually observable. What’s not so obvious is that roots are affected as spills of hydrocarbons infiltrate soil. This was demonstrated in 2017 when fluorescent dye was added to vegetable hydraulic oil.

Photo 2 Spatial distribution of a spill of vegetable hydraulic oil heated to 176 degrees on a plug of TifEagle hybrid bermudagrass. The oil contained fluorescent dye. Shining a UV light with a wavelength of 362 nm showed that the oil had spread over the shoots (left) and had infiltrated into the soil impacting roots and microorganisms (right).

The oil containing the dye, which fluoresces under UV light, was heated to 176 degrees F, and 0.1 fl. oz. was applied to the center of a 4-inch diameter plug of TifEagle hybrid bermuda-grass (Cynodon dactylon X C. transvaalensis) (Photo 2). Shining a UV light on the turf canopy (left) clearly showed shoots were covered with oil, as the dye fluoresced wherever oil had spread. Cutting the plug in half revealed that some of the oil had infiltrated to a depth of about 1 inch, affecting not only roots but root zone micro-organisms as well. Research to determine the spatial distribution of machine fluid spills begins this year.

Machine-fluid injury behavior is dynamic

The term “dynamic” refers to changes in a pattern or process with time. Injury resulting from spills of six different machine fluids, including brake fluid, diesel fuel, gasoline, motor oil, petroleum hydraulic oil and vegetable hydraulic oil were similar in some respects. For example, the injury area associated with spills of these machine fluids expanded with time to a maximum injury area, then contracted with time as healing of turf began. Shoots treated with machine fluids also lost visual green color with time, turning
from green to brown with onset of shoot necrosis. However, differences in the behavior of both injury area and visual green color loss have recently been documented.

Figure 1 Expansion and contraction of turfgrass injury area resulting from spills of 0.1 fl. oz. of gasoline and motor oil on a TifEagle hybrid bermudagrass green. Gasoline attained maximum injury area faster than motor oil. Motor oil injury began healing later and at a much slower rate. The Y axis is injury area and the X axis is time in days after treating.

Injury Area. The time it took to attain maximum injury area on TifEagle hybrid bermudagrass varied with machine-fluid type (Figure 1). Injury resulting from a spill of 0.1 fl. oz. of gasoline expanded to a maximum injury area of 4.6 sq. inch at 1.8 days after the spill event. This was determined using statistics known as nonlinear regression modeling. In contrast, injury resulting from a spill of 0.1 fl. oz. of motor oil expanded to a maximum of 4.2 sq. inch at 14.1 days after the spill. The maximum injury areas for these two fluids were similar, but it took 12 days longer for the injury from motor oil to reach its maximum area. In other words, the oil spread over the turf for 14 days after the spill. As a result, injury from motor oil began healing 12 to 13 days later at a much slower rate. Projected injury-area duration for the motor oil spill was estimated at 1,004 days versus 173 days for gasoline.

Ultimately, we discovered that injury areas from machine fluids having higher viscosity (i.e., motor oil and hydraulic oils) began healing later and had longer recovery times, with slower rates of healing, compared to machine fluids with lower viscosities (brake fluid, gasoline and diesel fuel). These differences may have been due to differences in biodegradability among fluids, as the literature suggests highviscosity petroleum hydrocarbons have relatively slow rates of biodegradation.

Figure 2 Changes in visual green shoot color with time in response to spills of 0.1 fl. oz. of gasoline and vegetable hydraulic oil. The Y axis is hue angle, which is a numerical descriptor of color. The X axis is days after treatment. Note how gasoline immediately caused loss of visual green color while color loss in response to vegetable hydraulic oil was more gradual. At 12 days after treating, all shoots were dead.

Visual Green Color Loss. The onset rate of shoot necrosis also varied with machine-fluid type (Figure 2). In other words, there were differences in how quickly the shoots died in response to spills. When 0.1 fl. oz. of gasoline was applied to TifEagle, the shoots became necrotic within 24 hours, which was evidence the shoots had been killed quickly. The visual green color half-life associated with gasoline was about six hours. In contrast, application of vegetable hydraulic oil resulted in a more gradual loss of visual green color; the visual green color half-life was 4.3 days. All shoots treated with brake fluid, diesel fuel, gasoline, motor oil, petroleum hydraulic oil and vegetable hydraulic oil were dead 12 days after treating. But the rate at which shoot death occurred differed significantly.

The nature of the fluids may explain these results. For example, gasoline contains high levels of constituents like toluene and benzene, which are lipid solvents. These compounds probably dissolved cell membranes quickly, killing shoots within 24 hours. Vegetable hydraulic oil, which does not contain significant amounts of lipid solvents, probably smothered the shoots/roots, resulting in a more gradual shoot death.

Volume influences injury; temperature doesn’t

Figure 3 Influence of volume on injury area for petroleum hydraulic oil (PHO) and vegetable hydraulic oil (VHO) spilled at ambient temperature (i.e., 95 degrees F). Injury response was linear for both oils. The PHO always resulted in larger injury area for a given spill volume, but shoots treated with VHO were just as dead.

The volume of a spill has a great deal of influence over injury area (Figure 3). Injury area on TifEagle hybrid bermuda-grass was directly proportional to the volume of machine fluid spilled, which makes sense. As spill volume increased from 0.03 fl. oz. to 0.17 fl. oz., injury area increased linearly for both petroleum hydraulic oil and vegetable hydraulic oil. Petroleum hydraulic oil always resulted in a larger injury area than vegetable hydraulic oil, but both oils killed shoots just as dead.

However, the temperature of the fluid at the time of the spill did not significantly influence the area of injured turf (Figure 4). There were no significant differences in injury area for hydraulic oils spilled at 95 degrees F or 176 degrees F. The notion that machine fluids need to be hot to kill turfgrass is a myth. Hot oils kill turf, but so do machine fluids at ambient temperature.

Figure 4 Influence of fluid temperature on injury area for petroleum hydraulic oil (PHO) and vegetable hydraulic oil (VHO). Shoots of TifEagle hybrid bermudagrass were treated with oil held at ambient temperature (95 degrees F) or heated to 176 degrees F, which was the estimated equipment operating temperature. Temperature of the fluid at the time of the spill was not a significant factor in injury area for either hydraulic oil. The PHO always resulted in a larger injury area, but shoots treated with VHO were just as dead, regardless of temperature.

Liquid detergent increases injury

Over the past 40 years, several methods for remediating machine-fluid spills have been described with limited success. A classic research example involved detergents, charcoal and calcined clays being applied to spills of various petroleum products. Researchers concluded that treating spills of hydraulic fluid and motor oil with detergent was an effective corrective treatment. Yet at two weeks after treating, only 45 percent turf cover was present, which in today’s world would be unacceptable.

Photo 3 Effect of washing spills of vegetable hydraulic oil heated to 176 degrees F on plugs of TifEagle hybrid bermudagrass with liquid dish soap. When plugs were left unwashed (bottom right), the injury was visible and distinct. Washing (top right) with detergent either injured all shoots directly (i.e., a detergent effect) or may have helped spread the spilled oil over a larger area, causing more extensive injury.

Research with liquid detergent and spills of vegetable hydraulic oil showed that applying liquid detergent after a spill may not be such a good idea (Photo 3). In this research, 0.1 fl. oz. of vegetable hydraulic oil was heated to 176 degrees then applied to pots of TifEagle hybrid bermudagrass. Half of the experimental units were left unwashed while the other half was treated with 1 fl. oz. of Dawn dishwashing detergent, then washed with a stream of water for 10 minutes. Distinct injury was visible where turf shoots were left unwashed. But where detergent had been applied and shoots were washed, injury appeared to be more extensive, affecting all shoots, not just those where hot oil made contact.

Based on this research, treating a hydraulic-oil spill with liquid detergent probably would not be the best choice in remediation tactics. Research now is being conducted to determine effective machine-fluid injury mitigation strategies.

You may reach William L. Berndt, Ph.D., Fort Myers, Fla., at leeberndt@aol.com or @Dr_Lee_Berndt for more information.


References
Berndt, W. L. 2007. Effect of synthetic hydraulic fluid on warm-season turfgrass. App. Turfgrass Sci. doi.org/10.1094/ATS-2007-1119-01-RS.
Berndt, W.L., J.W. Riger, and C.W. Riger. 2017. Nonlinear regression modeling of hydraulic oil injury on a bermudagrass green. Int. Turfgrass Res. Soc. J. 13: 1-10. doi: 10.2134/itsrj2016.04.0216.
Berndt, W.L., J.W. Riger, and C.W. Riger. 2018. Kinetics of hydrocarbon induced visual green color loss on a bermudagrass green. Agron. J. doi: 10.2134/agronj2017.08.0444.
Berndt, W.L. 2018. Does Hydrocarbon Fluid Type Influence Injury Area Dynamics on a Bermudagrass Green? Unpublished, in preparation.

All figures and photographs by Lee Berndt, Ph.D.

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1 Comment on "Hydrocarbon machine fluid injury on greens: What do we know?"

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  1. Paul Schofield says:

    Apply heavy doses of SUSTANE as soon as possible after a spill and brush it in

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