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Golf and Water Quality
Water. It descends from the clouds as rain to form streams, lakes, and seas. It's a major element of all living matter, an odorless, tasteless, slightly compressive liquid oxide of hydrogen, H2O. It appears bluish in thick layers, freezes at O C, and boils at 100 C.
Water is the principal reason that planet Earth is a habitable planet. Water is one of the most precious of our recyclable resources ... and its quality is our common concern. The volume of water utilized each day in the United States is the highest of any country in the world. Still, we have an adequate supply if it is wisely conserved, used, and recycled.
Yet the amount of water is not our only concern. Water quality is also a critical issue. The United States Golf Association (USGA) recognizes the importance of water quality--- for both groundwater and surface water. The USGA has taken positive actions to begin investigating the effects of golf course management practices on water quality. Between 1991 and 1994, ten research studies investigating pesticide and fertilizer effects were sponsored at 11 universities. This research provided useful preliminary information on pesticide and fertilizer fate, as well as testing and developing a variety of measurement devices and research methodology for turfgrass.
The USGA recognizes that the research it has sponsored is only a beginning. Understanding water quality issues will be essential to predict or simulate accurately the impact of managed turfgrass systems in a local environment. With objective information, the ability to identify true hazards to our health or the environment is increased, and turfgrass managers can take steps to best utilize the tools available in turfgrass management.
In an overview of all the sponsored studies, three conclusions are immediately apparent.
- First, turfgrass is a much more effective filter than cropland, and will require new prediction models to estimate pesticide and fertilizer fate accurately.
- Second, most fertilizers and pesticides showed little potential to affect groundwater and surface water quality. Turfgrass managers can take a few simple steps today to further reduce the chance of groundwater or surface water contamination.
- Finally, more research is needed. In some cases, these first studies showed results that were inconclusive or unexpected according to current models. In general, more work on pesticide runoff and volatilization is needed for additional soil types and climates across the United States. Maintaining water quality is critical to the long-term success of the turf industry. Both groundwater and surface waters must be protected through proper fertilizer and pesticide application practices. Research indicates that when pesticides and fertilizers are properly used, the chances for movement of these materials into ground or surface water are minimal. Each product needs to be carefully evaluated individually to assess product characteristics, site conditions, and environmental factors.
The remainder of this report is organized into four major sections:
- Defining Water Quality: this section introduces the basic terminology of water quality and the concept of pesticide and fertilizer fate.
- Leaching and Runoff: this section summarizes the factors that affect leaching (the movement of products through the soil into the groundwater) and runoff (surface water movement after storms or irrigation).
- Results of USGA-sponsored Research: listed by product.
- Reference List
Many issues fall under the banner of water quality. Certainly natural disasters like hurricanes and flooding can have a dramatic negative effect on the quality of groundwater and even surface water, rendering it unfit for human consumption without extensive treatment. As inhabitants of this planet, we also have a tremendous influence on the quality of our water. We are learning to take a critical look at several of the most common causes of groundwater and surface water contamination: industrial and community effluents; high-density urban areas with extensive paving and/or insufficient storm sewers to contain runoff; farming and livestock production practices; and simple human carelessness in disposing of household wastes.
For golf courses, water quality is often linked to the use of pesticides and fertilizers on the course and the potential for these chemicals to enter groundwater or surface water systems. USGA-sponsored research has focused on the factors influencing water quality.
Numerous golf course practices are already in place to maintain the quality of water while reducing the labor and energy costs required to sustain an excellent playing surface. For example, chemical control is only one approach used against pests by modern golf course superintendents. Superintendents select adapted turfgrasses with pest resistance and tolerance to climatic stress. They optimize turf growing conditions by ensuring that the proper amount of sunlight and air movement reach turf area. Attention to mowing heights and well-maintained equipment also help produce a healthy plant. The selection and proper application of fertilizers are carefully planned throughout the year. Finally, water management, through correct irrigation and adequate drainage, provides a healthy root system resistant to disease.
In addition to optimizing turf growing conditions, biological controls (such as predatory insects) and limited spot-spraying of pest infestations can be combined in a management system referred to as Integrated Pest Management (IPM). Chemical use has become more targeted and more efficient as this technique has evolved. Fertilizer use may decline where community effluent water is used to irrigate turfgrasses.
In recent years, controversy has sometimes surrounded the use of fertilizers and pesticides, even though similar products are used on home lawns. All products available on the market are carefully tested and then regulated by the Environmental Protection Agency. The USGA-sponsored research was designed to investigate how these products move through turfgrass and the soil/thatch profile.
Numerous practices are in place to help maintain quality.
- Adapted grasses with pest resistance
- Correct mowing heights
- Proper fertilization and irrigation
- Adequate drainage
- Integrated pest management
- Biological controls
Groundwater and surface water quality is affected primarily by two mechanisms: leaching and runoff.
Leaching is the downward movement of a pesticide or fertilizer through the soil and potentially into the groundwater. The degree to which a product leaches is affected by several factors:
- Soil type (products leach less in clay than sand).
- The degree to which fertilizers or chemicals bind to the soil.
- Persistence of chemicals or fertilizers in the soil.
- Solubility of the pesticide in water.
Runoff describes the movement of water across the turf and soil surface, such as what happens after a thunderstorm or heavy irrigation. If this water removes pesticides or fertilizers from the turf, then it can move these chemicals into streams, lakes, and rivers.
Many fertilizers and pesticides must penetrate the turfgrass to reach the soil and roots to achieve effectiveness. Yet when products penetrate too quickly, the result can be negative in several ways. First, the product may not perform as well as desired or expected. Second, the product may move below the root zone so the plant is unable to utilize the product. The applied product may continue moving through the soil and eventually enter the groundwater. Thus, it is in the interest of everyone to determine when leaching is likely to occur and how it can be prevented.
Leaching
Leaching is affected by environmental factors and the characteristics of the product.
Environmental Factors
Maturity of the turf can make a significant difference in the amount of leaching that occurs. A well-established, mature turf with some thatch will slow leaching.
In general, the USGA-sponsored studies found that pesticides and fertilizers which were properly applied to turfgrass did not leach in significant amounts. Levels of leaching were usually well below public drinking-water standards, measured as ppm (parts per million) or ppb (parts per billion). For purposes of comparison, one part per million is like a teaspoon in an average size swimming pool. One part per billion is like a teaspoon in 26 million gallons of water.
Soil texture describes the size of soil particles (i.e., sand, silt, and clay) in a soil. Soils that have smaller, flatter particles - like clay - have more surface area and chemical charge. Fine clay has about 10,000 times as much surface area as the same weight of medium-sized sand. Pesticides or fertilizers tend to bind or adsorb to this larger surface area. Thus, all other factors being equal, soils with some clay particles are more likely to tie-up pesticides and fertilizers, potentially reducing the amount that can move into the groundwater.
Sandy soil, on the other hand, has large particles and less chemical charge. These particles offer the pesticide or fertilizer less surface area for adsorption. Thus, very sandy soils are likely to have more potential for leaching. When sandy soils are amended by organic matter (for example sphagnum peat moss is added), more surface area and charge are present. The increased surface area and charge available in amended soils slows leaching. Putting greens built to USGA recommendations, which contain a mixture of sand and peat, improves water retention and the ability of the soil to bind or adsorb chemicals. Greens built in this manner reduce fertilizer and pesticide leaching.
Soil moisture can also affect leaching. Generally, dry soils will have more capacity or space for water than wet soils. Excessive irrigation or rainfall can increase the risk of products moving downward through the soil profile into groundwater or transported by runoff water into surface water bodies.
Characteristics of the product
Pesticide and fertilizer binding properties affect leaching as well. Because of their chemical properties, some products are more likely to adsorb or bind to soil particles than others. Products used in the turf industry encompass a wide range of binding properties. In general, products that bind more tend to leach less. Soil scientists use a term called Koc to predict binding potential. Most pesticides used in turf have the advantage of binding to soil and thatch, thereby reducing the chance for movement into groundwater. A Koc value of less than 300 to 500 is considered low, and may indicate the potential for leaching in some situations.
Persistence describes how long products last before they are metabolized or broken down. Products that last longer before metabolizing may be more effective; however, a product that is in the soil longer also has more time to leach into groundwater. Persistence is determined by several factors, but principally by how the product degrades.
Some products degrade faster in sunlight (photochemical degradation). Others degrade faster when in contact with water (chemical degradation). Some products enter a gaseous state (volatilization). And finally, most pesticides and fertilizers are broken down to some degree by the action of soil microbes (microbial degradation). Scientists use the term half-life (expressed as DT50) to describe how many days it takes for 50 percent of the original pesticide to break down into other products, called metabolites.
Solubility is defined as the ability of a chemical to dissolve in water. The solubility of a pesticide must be considered in conjunction with the other factors.
Use rate: A pesticide that is used at high rates may leach into water if it also meets several of the above criteria (long persistence, low binding ability and high solubility). Most newer pesticides have low use rates.
On the following pages, results of the leaching studies are presented by product name. This allows quick reference to the potential environmental fate of each product and associated management recommendations. However, it should be noted that several studies intentionally simulated "worst-case" scenarios (i.e. pure sand, high rainfall, a chemical known to leach) to investigate the range of leaching potential under a variety of conditions.
Runoff
Surface water features such as ponds, lakes, and streams are an integral part of many golf courses and landscapes. They not only provide a valuable source of irrigation water and habitat for fish and wildlife, but also add challenging obstacles for golfers.
Protecting surface water requires good planning by turf managers to prevent accidental pesticide and fertilizer contamination. The most common reason for surface water contamination by fertilizers or pesticides is heavy rainfall soon after application, before the material has moved into the soil or thatch. Heavy rainfall can move the pesticide or fertilizer because it has remained on the surface and not yet had a chance to be adsorbed by the soil, used by the plant, or broken down in the soil. Sloping terrain, thin turf, and poorly drained or compacted soils can also contribute to the potential movement of fertilizers and pesticides into surface waters.
Several encouraging developments have reduced the potential for pesticide and fertilizer movement into surface waters. New pesticides are used at lower rates and degrade faster in the environment. This reduces the chances for surface water contamination. Golf course superintendents are highly trained to do a better job of applying pesticides and fertilizers. Newer, more technologically advanced equipment improves the placement of these materials. By raising the awareness of turf managers to be more careful with pesticides and fertilizers applied near water, the chances for surface water contamination are significantly reduced.
The USGA sponsored research to determine the impact of several pesticides and fertilizers on groundwater and surface water. Three types of pesticides were studied: insecticides, herbicides and fungicides. Nitrogen and phosphorus fertilizer were also studied. The following table provides a brief summary about the products studied.
| Product |
Common Name |
Product Type |
Location of Study |
| carbaryl |
Sevin® |
Insecticide |
University of California |
| chlorpyrifos |
Dursban® |
Insecticide |
University of Florida
Iowa State University
University of Nebraska
University of Georgia |
| ethoprop |
Mocap® |
Insecticide |
University of Florida |
| fenamiphos |
Nemacur® |
Insecticide |
University of Florida |
| fonophos |
Dyfonate® |
Insecticide |
University of Florida |
| isazofos |
Triumph® |
Insecticide |
University of Florida
Cornell University
Iowa State University
University of Nebraska
Michigan State University
Pennsylvania State Univ.
Univ. of Massachusetts |
| isofenphos |
Oftanol® |
Insecticide |
University of Florida
Univ. of California |
| 2,4-D phenoxy |
2,4-D |
Herbicide |
University of Georgia
University of California
Michigan State University
University of Florida |
| dicamba |
Dicamba |
Herbicide |
University of Georgia
Michigan State University
University of Florida |
| dithiopyr |
Dimension® |
Herbicide |
University of Georgia |
| mecoprop |
MCPP |
Herbicide |
University of Georgia
Cornell University
Pennsylvania State Univ. |
| pendimethalin |
Pendulum® PreM® |
Herbicide |
University of Nebraska
Iowa State University |
| nitrogen |
|
Fertilizer |
Michigan State University
Iowa State University
Pennsylvania State Univ.
Washington State Univ.
Cornell University
Univ. of California |
| phosphorus |
|
Fertilizer |
Michigan State University
Iowa State University
Pennsylvania State Univ. |
| metalaxyl |
Subdue® |
Fungicide |
University of Nebraska
Iowa State University
Michigan State University |
| triadimefon |
Bayleton® |
Fungicide |
Michigan State University
Cornell University
Univ. of Massachusetts |
| chlorthalonil |
Daconil® |
Fungicide |
Michigan State University
University of Georgia |
| fenarimol |
Rubigan® |
Fungicide |
Michigan State University |
| propiconazole |
Banner® |
Fungicide |
Michigan State University |
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Insecticides
Carbaryl (Sevin®) is a widely used carbamate insecticide. It has a low water solubility (114 ppm), very short half-life (10 days) and medium binding potential in soil (Koc of 200). Due to its short half life, it is very unlikely that this insecticide will leach from the soil. At the University of California-Riverside, very little carbaryl was detected in lysimeters located beneath simulated golf green and fairway plots (the range was 0.0015% to 0.07% of the total applied). The lack of movement in soil is most likely related to the rapid degradation of the insecticide by soil microbes.
Chlorpyrifos (Dursban®) is an organophosphate insecticide used to control a broad range of insect pests. Chlorpyrifos degrades slowly, with a half-life of 60 to 120 days. It has a low solubility (0.4 to 4.8 ppm) and low potential to move through the thatch and root zone (Koc of 2,500 to 14,800). At University of Florida's Fort Lauderdale Research and Extension Center, chlorpyrifos leaching was small (0.15% of that applied) after the first application to putting greens. After a second application, a smaller amount leached (0.08% of that applied), even though the application rate was doubled and the percolation rate (speed at which water moves through the soil) increased five-fold.
At the University of Georgia, three applications of chlorpyrifos in a 10-week period resulted in no leaching from field plots. Joint studies at the University of Nebraska and Iowa State found that very little chlorpyrifos moved through the thatch layer into the underlying soil, and even smaller amounts were found below a depth of two inches. These studies indicate little potential for chlorpyrifos leaching, even under heavy irrigation or rainfall in combination with amended sand soils.
Ethoprop (Mocap®) is an organophosphate insecticide used to control nematodes and turf insects. It is slightly soluble in water (700 to 750 ppm), has a medium half-life in soil (14 to 63 days) and has moderate to weak binding potential in bare soil (Koc of 26 to 120). When ethoprop was applied to a USGA green in the University of Florida study, only 0.05% of the total amount applied was detected in water that leached through the amended sand green. Nearly 60% of the ethoprop was found in the thatch one month after application. A small portion moved into the soil, and the remaining amount is believed to have degraded in the thatch layer.
Fenamiphos (Nemacur®) is an organophosphate insecticide with systemic activity (moves into and within the plant) and is primarily used to control nematodes. It has a short half life in soil (3 to 30 days), intermediate water solubility (400 to 700 ppm) and medium ability to leach in bare soil (Koc of 26 to 249). At the University of Florida's Research and Extension Center, fenamiphos was applied to an amended sand green. The majority of the fenamiphos breakdown products (metabolites) were found one week after application in the thatch. These breakdown products then moved from the thatch and into the upper soil layers. The metabolites (sulfoxide and sulfone) are believed to be more water soluble, which would account for their downward movement. More conservative management practices may be warranted when fenamiphos is used on golf courses, and further investigations are underway to better define management practices with this product.
Fonophos (Dyfonate®) is an organophosphate insecticide used to control many soil-borne turf insects. It has an intermediate half-life in soil of 45 days, low water solubility (13 ppm) and medium ability to bind to soil (Koc of 532). These factors would indicate a low to medium ability to leach in bare soil. When fonophos was applied to an amended sand green in a University of Florida's Fort Lauderdale Research and Extension Center, very little movement occurred. Researchers found the majority of the fonophos in the thatch, and a negligible amount was found in water that leached through the green. The extremely low water solubility of fonophos is the most likely reason for the lack of leaching.
Isazofos (Triumph®) is an organophosphate insecticide that is slightly soluble in water (150 ppm) and has a half-life of 34 days. This insecticide has a restriction indicating it should not be applied to sandy soils. Research conducted at Cornell University suggests that isazofos may leach through sandy soil, but very little leaching would occur in sandy loam or silt loam soils. The insecticide was applied to fairways with different soil textures (sand, sandy loam, and silt loam), and leachate (water moving through the fairways) was collected.
On fairways constructed of straight sand, 8% of the total isazofos was found in leachate. On sandy loam fairways, only 0.06% of the total amount of isazofos was found in leachate. On silt loam fairways, 0.46% of the total amount of isazofos applied was found in leachate.
In University of Florida research, very little of the total isazofos applied (0.09%) was found to leach through an amended sand green. This suggests that there is little isazofos movement in sandy soils with adequate organic matter. University of Nebraska research also reported that isazofos degraded rapidly and was immobile in the soil. In the Michigan State University study, isazofos leaching was not significant. A Pennsylvania State study found 470 ppb (perennial ryegrass) and 514 ppb (bentgrass) isazofos in runoff from irrigated fairways the day after application. Eight weeks after application, no isazofos was found in the runoff produced by six inches per hour of irrigation.
Isofenphos (Oftanol®) is a rapidly degraded organophosphate insecticide that is used primarily to control white grubs, chinch bugs, and sod webworms. It has a low water solubility (24 ppm) and a low ability (Koc of 760) to leach in bare soil. Due to its extremely rapid microbial degradation, it has little chance to move downward within the soil. When isofenphos was applied to an amended sand green at the University of Florida's Fort Lauderdale Research and Extension Center, 13% of the total amount applied was found in the thatch and soil six days following application. No isofenphos was found in soil or thatch beyond 21 days after application. Only 0.02 percent of the total amount of product applied leached through the amended sand green during the entire study.
Herbicides
2,4-D has been one of the most widely used and studied herbicides on home lawns and golf courses. It was the first widely used selective herbicide in the United States. It has a medium water solubility (890 ppm), a short half-life in soil (10 days), and a moderate to weak binding potential on bare soil (Koc of 20). In research at Michigan State University, no significant amounts of 2-4,D could be detected in the water that leached through a sandy loam soil. At the University of California, Riverside, more 2,4-D was found in leachate from greens (average of 4.1% of total applied) than fairways (average of 1.3% of the total applied). In both cases, though, the amount of leachate amounts is most likely due to the different soil textures. The fairway-type soils reduced leaching because they had more silt and clay (a higher binding ability). 2,4-D is used on greens in very small quantities, if at all.
At the University of Georgia, surface water samples were collected and analyzed for 2,4-D. These plots received a high volume of water (2 inches per hour) and were located on sloping ground (5%). Under these conditions, 10 percent of the total amount of 2,4-D applied was found in runoff water 24 hours after application. Precautions should be taken when 2,4-D is used near surface water or on very sandy soils.
Dicamba is a broadleaf herbicide that is often used in combination with 2,4-D. The herbicide is very soluble in water (500,000 ppm), has a short half-life in soil (14 days), and weak binding potential in soil (Koc of 2). The chemical characteristics of dicamba would imply that it has a high leaching potential. However, the herbicide is used at relatively low rates and is rapidly degraded in soil by microbes. The low use rate combined with rapid degradation limits the amount that moves through the soil. At Michigan State University, dicamba was detected in leachate about 6 weeks after application at levels of up to 3 ppm. In a University of Georgia study, 0.13% of the total amount of dicamba applied to an amended sand putting green was found in lysimeters one week after application.
Dithiopyr (Dimension®) is a new turf herbicide that is used primarily to control weedy grasses. The herbicide has a low water solubility and is adsorbed to soil and organic matter. The average half-life of the herbicide is 17 to 64 days. The herbicide is rapidly taken up by turf plants, which helps reduce the chances for movement into groundwater or surface water. At the University of Georgia, the herbicide required considerable amounts of water before it moved through an amended sand soil. There was no difference in the amount of movement between turf species used on the putting green (bermudagrass vs bentgrass). Less than 0.35% of the total dithiopyr applied was found in leachate.
Mecoprop (MCPP) is a systemic herbicide that is used to control broadleaf weed species in turf. It has a similar mode of action to 2,4-D. The herbicide has a relatively short half-life of 21 days. It is very insoluble (0.62 ppm) in water, and its binding potential to soil is dependent on its specific formulation. At the University of Georgia, on amended sand greens, only 0.2% and 0.08% of the mecoprop applied was found in lysimeters. The difference in detection was due to the higher amounts (80:20 sand to peat ratio vs a 85:15) of peat used for green construction in the second study.
At Cornell University, MCPP was applied to simulated golf fairways with different soil textures. The greatest amount of MCPP movement occurred on immature turf grown on sandy soil that received large amounts of precipitation. Movement was reduced considerably when applications were made to fairways with silt loam or sandy loam soil textures. The decrease in leaching is due to the increased herbicide binding to clay or organic matter in these soils compared to sand. Few golf fairways have 100% sand as the primary soil texture.
At Pennsylvania State University, mecoprop was applied to two different turf varieties (bentgrass and perennial ryegrass) receiving management as a golf fairway. Water was collected as runoff and after movement through lysimeters. At all sampling intervals except 24 hours after application, the concentration of mecoprop was less than 100 parts per billion or not detectable at all. There was no difference in its movement between grass species.
Pendimethalin is used to control grassy weeds in turf. It has a low water solubility (0.275 ppm), medium to long half-life (90 days), and very strong binding potential in soil (Koc of 24,300). The strong binding potential suggests that it is difficult for the herbicide to move through soil. At the University of Nebraska and Iowa State University, pendimethalin was applied to turfgrass. Movement through thatch and soil was monitored by taking soil samples at different depths. Very small amounts of pendimethalin reached the soil. Most of the herbicide was found in the thatch. This lack of movement was believed to be due to the low water solubility and strong binding of the herbicide. Researchers also found that between 14 and 20 days were required for the herbicide to be degraded by half.
Fungicides
Metalaxyl (Subdue®) is a systemic fungicide that is used to control turf disease. The fungicide has a moderate solubility (7,100 ppm), a relatively short half-life (21 days), and a weak binding potential in soil (Koc of 16). Due to its weak binding potential and its water solubility, there could be potential downward movement in soil. In the University of Nebraska and Iowa State University studies, the most metalaxyl was found in the top four inches of soil with detectable amounts as deep as 12 inches. The half-life of metalaxyl in the turf environment is 12 to 20 days. Data from Iowa and Nebraska suggest that metalaxyl has the potential for movement in soil, but the amount moved is limited by the relatively rapid degradation of the fungicide.
Triadimefon is a systemic fungicide used to control turf diseases. It has a low water solubility (260 ppm), medium half life (30 days) and is moderately adsorbed to soil (Koc 205). A Michigan State University study confirmed that only a small concentration of triadimefon (32 ppb) was found in water that drained from a lysimeter located four feet below the turfgrass surface.
Fertilizers
Nitrogen fertilizers are used extensively in turf and agriculture. Adequate nitrogen levels are needed to ensure growth of grass, since nitrogen is an important component of all plant proteins. The atmosphere is nearly 80% nitrogen, but turfgrasses do not have the ability to use it. Therefore, turfgrasses must get needed nitrogen from other sources. Most of this nitrogen is obtained from fertilizers that are applied at different times of the year.
Nitrogen can be found in many different chemical forms. Of these different forms, nitrate (NO-3) nitrogen has the most potential for movement into groundwater. Nitrate-nitrogen can move through soil because it has a negative chemical charge, which can prevent strong binding with clay and organic matter.
The USGA has sponsored several studies to investigate the impact of nitrogen on water quality. At Michigan State University, researchers found that only very small amounts of nitrogen leached through soil, regardless of when it was applied to turfgrass. This lack of downward movement is due to utilization of the nitrogen by the turf plant. The organic matter that is created by dead turf may also act as a nitrogen sponge. Finally, some of the nitrogen was lost due to volatilization (formation of gas). This loss is a normal process in the nitrogen cycle.
At Washington State University, nitrogen was applied to greens constructed primarily of sand. Here, researchers discovered seasonal movement of nitrate nitrogen into lysimeters. The movement was greatest in newly established greens, compared to mature greens with better root systems, and subsequently, better nitrogen utilization. The addition of organic matter to the putting green root zone significantly reduced the amount of nitrate nitrogen collected in the lysimeters.
A joint University of Nebraska and Iowa State University study indicated that nitrogen may move as far as 20 inches through turf and soil if a significant amount of irrigation water is applied. The researchers found that as more water is applied, the likelihood for nitrogen movement increases. This movement could be controlled with lighter, more frequent applications of water (0.5 inch), compared to one large dose (1.0 inch). Applications of 0.5 inch of water are much more common in turf irrigation than single doses of 1.0 inch or more.
In a Pennsylvania State University study, nitrogen fertilizers were applied to two different species of turf maintained as fairways to determine runoff and leaching potential. In the three years of the study, very little fertilizer nitrogen was found in runoff water or leachate. The concentration of nitrogen in these waters was generally lower than the levels found in the water used to irrigate the turf. The researchers also found that creeping bentgrass turf produced less runoff than ryegrass. Both turf species, however, were effective at reducing nitrogen movement when they were maintained as golf course fairways. This difference in nitrate movement was due to the dense growth habit of creeping bentgrass. This grass produces more tillers, resulting in a more dense turf with more thatch than perennial ryegrass.
Researchers at the University of California found similar results. They found only a small amount (0.30 % to 1.71% of the total amount applied) of nitrogen moved into the lysimeters under greens and fairways. Nitrogen movement increased as the sand content of the green or fairway increased. This was expected, since sand has less chemical charge (or binding ability) than soils with higher clay and silt content.
These studies suggest that nitrogen fertilizers must be properly applied and managed in turf environments. Proper application and management includes adjusting the rate and form of product according to the soil type and expected rainfall or irrigation. With these precautions, the chances for movement of nitrogen from application sites on established turf to groundwater or surface water are greatly reduced, and the chances for significant off-target movement with normal use are minimal.
Phosphorus (P205) is also applied to turf to support healthy plant and root growth. Phosphorus generally does not move in soil because it binds with clay, aluminum, and calcium. It also is applied less frequently and generally at much lower rates than nitrogen fertilizers.
In a Michigan State University study, movement of phosphate fertilizer (P2O5) was studied on greens with different soil types. In all cases, the amount of movement was minimal. The maximum depth of movement was 8.75 inches, with most P2O5 found above 5.75 inches. Movement was greater in the greens with a higher sand content, because sand has less binding potential than soils with higher levels of organic matter or clay.
Iowa State University and University of Nebraska research studied phosphorus movement under greenhouse conditions, using turf and soil that was removed from a golf course. In this study, small amounts of elemental phosphorus moved as far as 20 inches. Movement was greatest when large amounts of irrigation water were applied. The researchers believe that some of this movement occurred due to the macropores (worm burrows, old root channels etc.) present in the excavated turf/soil sections. This movement was deeper than expected, but the amounts found were small, and should pose no threat to the environment.
Summary
Maintaining water quality is critical to the long-term success of the turf industry. Both groundwater and surface waters must be protected through proper fertilizer and pesticide application practices. Research indicates that when pesticides and fertilizers are properly used, the chances for movement of most of these materials into ground or surface water are minimal. Each product needs to be carefully evaluated to assess product characteristics, site conditions, and environmental factors.
Bowman, Daniel C., D. A. Devitt and W. W. Miller. 1993. The Effect of Salinity on Nitrate Leaching from Turfgrass. USGA Green Section Record 33(1):45-51.
Bowman, Daniel C., D. A. Devitt, and W. W. Miller. University of Nevada. 1994. The Effect of Salinity on Nitrate Leaching from Turfgrass. p. 380-432. In USGA Environmental Research Program: Pesticide and Nutrient Fate - 1991-1993 Summary. United States Golf Association, Far Hills, NJ.
Branham, Bruce E. Michigan State University. 1994. Groundwater Contamination Potential of Pesticides and Fertilizers Used on the Golf Course. p. 239-258. In USGA Environmental Research Program: Pesticide and Nutrient Fate - 1991-1993 Summary. United States Golf Association, Far Hills, NJ.
Branham, Bruce, E. Miltner, and P. Rieke. 1993. Potential Groundwater Contamination from Pesticides and Fertilizers Used on Golf Courses. USGA Green Section Record 33(1):33-37.
Brauen, Stanton E. and G. K. Stahnke. 1993. Leaching of Nitrate from Sand Putting Greens. USGA Green Section Record 33(1):29-32.
Brauen, Stanton E. and G. K. Stahnke. Washington State University. 1994. Quantification and Fate of Nitrogen from Amended Sand Putting Green Profiles. p. 107-132. In USGA Environmental Research Program: Pesticide and Nutrient Fate - 1991-1993 Summary. United States Golf Association, Far Hills, NJ.
Cooper, Richard J., J. M. Clark, and K. C. Murphy. 1993. Volatilization and Dislodgeable Residues Are Important Avenues of Pesticide Fate. USGA Green Section Record 33(1):19-22.
Cooper, Richard J. and J. M. Clark. University of Massachusetts. 1994. Volatilization and Dislodgeable Residues of Pesticides and Nutrients Applied to Golf Turf. p. 348-379. In USGA Environmental Research Program: Pesticide and Nutrient Fate - 1991-1993 Summary. United States Golf Association, Far Hills, NJ.
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