June 19, 2000
ENVIRONMENTAL EFFECTS OF LAWN TREATMENT
By: Kevin E. McCarthy
You asked for a description of research conducted by Connecticut or other states on the environmental effects of commercial lawn care, particularly groundwater contamination.
We did not find any research conducted by or for states on this specific topic. However, we found research in Connecticut, Maine, Massachusetts, Minnesota, Ohio, and Pennsylvania on the broader issues of pesticide contamination of groundwater and fertilizer contamination of surface waters. The data are limited but suggest that, when properly applied, the use of pesticides and fertilizer by lawn care companies does not significantly threaten these resources. We will provide citations to these studies upon request.
On the other hand, the improper or excessive use of pesticides and fertilizers, whether by commercial lawn care companies or homeowners, can cause groundwater contamination and other environmental problems.
Lawn care companies routinely apply pesticides and fertilizer to lawns. Pesticides are designed to kill organisms such as insects (insecticides), weeds (herbicides), and mold or fungus (fungicides). Pesticides include active ingredients which are designed to kill the target organisms and inert ingredients, which may also have harmful effects. The fertilizers applied by lawn care companies generally include nitrogen, phosphorous, and potassium.
The primary concern about the pesticides used in lawn care is that they can leach through the soil and contaminate the groundwater. Pesticide leaching depends, in part, on the chemical and physical properties of the pesticide. For example, a pesticide held strongly to soil particles is less likely to leach. Solubility is another factor because a pesticide that dissolves in water can move with water in the soil. The persistence, or longevity of a pesticide also influences the likelihood of leaching. A pesticide that is rapidly broken down by a degradation process is less likely to leach because it may remain in the soil only a short time.
The improper use of pesticides can also harm beneficial insects, animals, and the applier. If a pesticide is overused, the pests can become resistant to it. Pesticides can also be carried by runoff into streams and lakes, where they jeopardize aquatic life. The environmental effect of a pesticide may be influenced by such factors as its volatility, its method of application, the type of formulation, soil and plant characteristics, its solubility of the pesticide, adsorption on soil or plant surfaces, the persistence, and climatic conditions. The Web site of the Rachel Carson Council, an environmental advocacy group, describes potential environmental and health effects of pesticides used in lawn care http://members.aol.com/rccouncil/ourpage/samples.htm#lawns.
The primary concern about fertilizers (particularly nitrogen and phosphorous) is that they run off into streams and other water bodies, particularly when they land on sidewalks and driveways. The runoff flows into water bodies where it causes rapid growth of algae. This growth reduces oxygen levels and harms fish and other organisms. This process, called eutrophication, is a particular problem in the eastern part of Long Island Sound. As is the case with leaching, runoff is affected by many factors. These include the slope of an area; the characteristics of the soil; and the amount and timing of rainfall or watering.
A second concern about nitrogen in fertilizer is that its nitrate form may leach into groundwater supplies. The nitrogen in nitrate is not bound to soil particles and can move through the soil with water. Once beyond the root zone, nitrates can continue moving through the soil and may find their way into ground water as well as surface water sources.
We were unable to find research on the specific issue of the impact of commercial lawn care but found research conducted by and for states on several related issues. These include pesticide contamination in groundwater in urbanized versus other areas, pesticide contamination below golf courses, and nitrogen runoff from fertilized turfed areas, such as lawns and golf courses. None of these focus on commercial lawn care per se, although golf courses are normally treated professionally.
Universities, the lawn care industry, and environmental agencies have produced many documents on best management practices to reduce these risks. Examples of relevant Web sites include http://www.uidaho.edu/wq/wqbr/, http://www.trugreen.com/, and http://www.dnr.state.wi.us/org/water/dwg/gw/bhgwater.htm. There is also a large body of research on the general topic of integrated pest management, which has identified many techniques to reduce the use of pesticides.
SA 86-44 required the Department of Environmental Protection, in conjunction with the Agricultural Experiment Station and the United States Geological Service, to study pesticide contamination of groundwater. The department issued its report, which is available in the Legislative Library, in December 1991. The study tested 89 wells at 59 sites, of which 32 were farms, 17 were golf courses, and 10 were residences. The study found 24 different pesticides at 39 sites, most at very low levels. The most commonly discovered pesticides were atragari (found at 25 sites) and DCPA (found at 15 sites). While the report notes the types of pesticides discovered and the land use of the site, it does not discuss the source of contamination.
A 1999 study conducted by the state Department of Environmental Protection found no statistically significant difference in nitrate nitrogen levels in 214 wells in residential lots that were fertilized and 191 that were not. Further information about the study is available at
Two studies of golf courses on Cape Cod published in 1990 provide evidence that lawn care products applied to turfgrass do not leach into groundwater. Four courses were selected as likely to have groundwater contamination based on their permeable, sandy soils; history of high pesticide and fertilizer use; and age (at least 30 years). The researchers argued these courses should represent a worst case scenario for potential groundwater contamination. The study detected no trace of seven pesticides-mecoprop (MCPP), siduron (Tupersan), pentachlorophenol, anilazine (Dyrene), iprodione (Chipco 26019), diazinon, and dacthal. The highly mobile herbicides 2,4-D and dicamba were detected only once each in about 70 samples, both in amounts well below their health advisory limit values. Isofenphos (Oftanol) was detected once and chlorothalonil (Daconil) was detected twice. In all instances, detection values were below stated health advisory limit values. Finally, none of the currently registered turfgrass pesticides was detected at toxicologically significant levels.
The University of Minnesota extension service published a report in 1997 on the effects of turfgrass maintenance on ground and surface waters http://www.extension.umn.edu/distribution/horticulture/DG5726.html. Several studies summarized in the report found that the amount of nitrogen carried in runoff from turfed areas was very low. That is because turf has many closely spaced plants forming a relatively closed canopy over the soil surface. The density and height of the canopy combine with the texture of blades of grass to resist the movement of water over turf. In most cases the contamination in the runoff was much less than the Environmental Protection Agency established drinking water standard. The extensive fibrous root system located in the upper two inches of the soil (the root zone) also helps minimize runoff.
Studies summarized in the report found that fertilizer leaching problems are greatest: (1) on coarse-textured soils such as sands and sandy loams; (2) when quick-release nitrogen sources are applied at high rates followed by heavy irrigation or rainfall; and (3) when a quick-release source of nitrogen is applied when the grass is not actively growing. Other studies summarized in the report describe the potential impact of the phosphorous in fertilizer and the phosphates formed when it breaks down chemically.
Research conducted at Ohio State University found that insecticides seldom penetrated more than 1.5 inches below the grass. When isazophos (Triumph), isofenphos (Oftanol), ethoprop (Mocap), chlorpyrifos (Dursban), and bendiocarb (Turcam) were applied to a golf course fairway, 98% to 99% of the residue remained in the thatch layer 1 to 2 weeks after application. Residues in the one inch of soil below the thatch never exceeded 0.8 parts per million during the 34-week sampling period.
Similar Ohio research evaluating the downward mobility of several herbicides used to kill weeds before they emerge from the ground noted that 77% to 100% of the pendimehtalin, bensulide, and oxidiazon residues remained in the thatch layer. When applied to turf without thatch, 82% to 99% of recovered residues from these materials stayed in the upper one inch of soil. Other research has shown that pendimethalin is relatively immobile and generally does not leach from turfed areas into the groundwater.
Further information about these studies is available at http://www.ag.ohio-state.edu/~ohioline/b820/index.html. This report also discusses variations in pesticide persistence and soil permeability, which affect the extent to which a pesticide affects groundwater
Research at Pennsylvania State University has shown that even under extreme conditions, the amount of runoff from sodded golf course slopes is small. The herbicides 2,4-D, 2,4-DP, dicamba, and pendimethalin, were not detected in most runoff samples, and when detected, the concentrations were low. No chloropyrifos was detected in any of the samples. In a later study, neither pendimethalin nor chlorpyrifos was detected from turfed slopes in runoff or leachate samples.