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a Soil Science Department, North Carolina State University, Box 7619, Raleigh, NC 27695
b North Carolina Department of Agriculture and Consumer Services, Agronomic Division, 4300 Blue Ridge Road, Raleigh, NC 27607
* Corresponding author (deanna_osmond{at}ncsu.edu).
Received for publication November 30, 2002.
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMETHODSRESULTSDISCUSSIONCONCLUSIONSREFERENCES |
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONCONCLUSIONSREFERENCES |
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The sources of pollution are diverse, although the majority of the pollutants are delivered from nonpoint sources as opposed to point sources. The USEPA estimates that agriculture contributes 53%, construction 10%, mining and other activities 13%, miscellaneous sources 12%, and urban runoff 12% to the nonpoint-source pollution load in the USA (USEPA, 1995). Since nonpoint-source pollutants originate from urban, as well as agricultural lands, it is essential to assess the effects of lawn care practices, especially in residential areas.
Although urban N nonpoint-source pollution originates from inputs of animal and plant waste, septic systems, atmospheric deposition, and N fertilizer, N fertilizer use in the landscape (primarily turf) is expected to contribute the largest load of N into urban streams. In North Carolina, as in many other locations throughout the USA, no urban fertilizer-use statistics exist and little is known about turf fertilization practices of typical residents.
Although no urban fertilizer use data in North Carolina exist, limited information as related to mass transport and loss of N in addition to characterization of surface waters is available. Established residential areas, golf courses, and new construction sites measured higher N mass losses than a fescue pasture or newly established residential areas (Line et al., 2002). Preliminary water quality data from urban streams associated with different land uses in the upper Neuse River basin document median nitrate nitrogen (NO3–N) concentrations ranging from almost nondetectable to approximately 1 mg L–1 (G.D. Jennings, personal communication, 2002). Additional urban stream monitoring data from Charlotte, NC generally report stream concentrations around 2 mg L–1 total N, with the majority of the N as organic N rather than NO3–N (Bales et al., 1999). These urban stream data from the Neuse River basin are similar to NO3–N concentrations measured in urban streams throughout the United States. Storm runoff data records from throughout the United States were reviewed for 37 residential watersheds with the average concentration clustered around 0.6 mg L–1 NO3–N, with a range of 0.25 to 1.4 mg L–1 (Barth, 1995). Both state and national urban stream N concentrations are lower than the NO3–N concentrations frequently measured (3–5 mg L–1) in predominantly agricultural areas in the middle Neuse River basin (Gilliam et al., 1997).
The contribution of turf fertilization to total N nonpoint-source losses appears to be relatively small on a river basin scale. Researchers have measured only small amounts of N in surface runoff from turf (Gross et al., 1990, 1991; Hipp et al., 1993). These results reflect the fact that most water generally moves through turf, rather than over turf, and that most applied N, unless in a slow release or organic form, is readily converted to NO3–N and moves through the soil profile rather than being lost through runoff. Since grasses are perennials with extensive root systems, well-managed turf should have relatively high fertilizer N-use efficiency and thus lower leaching losses. The range of fertilizer N-use efficiency has been measured from 25 to 99%, depending on grass species, fertilization rate, fertilizer formulation, and soil type (Petrovic, 1990).
Leaching losses of N under turfgrass appear to be low. Under various turfgrass management practices, researchers have measured average NO3–N concentrations ranging from 1 to 30 mg L–1 (Geron et al., 1993; Morton et al., 1988; Walker and Branham, 1992). The only conditions that resulted in the higher NO3–N concentrations were typically sandier soils with high N fertilizer rates. A recent nitrate leaching study on extremely well-managed golf courses in North Carolina demonstrated shallow ground water NO3–N concentrations from negligible to 12 mg L–1, with the greater shallow ground water N concentrations occurring on sandy soils (Adams, 1999). Gold et al. (1990) measured NO3–N in shallow ground water from forest, fertilized and unfertilized home lawns, septic systems, and silage corn (Zea mays L.). Significantly higher amounts of N were leached through the soil profile into the ground water from the corn system (66 kg ha–1 per year) and septic systems (48 kg ha–1 per year) than the forest system (1.4 kg ha–1 per year), fertilized lawn (6 kg ha–1 per year), and unfertilized lawn (1.4 kg ha–1 per year). Compared with fertilized cornfields that may routinely measure greater than 10 mg L–1 NO3–N, leaching concentrations under turf appear to be low, generally around 3 mg L–1 NO3–N (Geron et al., 1993; Morton et al., 1988; Walker and Branham, 1992; Adams, 1999).
Turfgrass management may be the most critical factor determining NO3–N leaching. Several researchers have observed that regardless of fertilizer formulation (slow release vs. regular fertilizer), leachate concentrations did not differ (Geron et al., 1993; Gross et al., 1990; Mancino and Troll, 1990). Water quantity, however, has a marked effect on the movement of NO3–N. Excess irrigation of lawns appears to be a controlling factor determining the amount of NO3–N leached (Schueler, 1995).
The North Carolina Environmental Management Commission (NCEMC) is the environmental rule making committee for the State of North Carolina. The NCEMC instituted point and nonpoint source rules for the Neuse River basin that became effective 1 Aug. 1998 (North Carolina Department of Environment and Natural Resources, 1997a). Estimates for N pollutant loads from the different sectors (agriculture and urban) are somewhat uncertain, although the total load is measured at approximately 3.6 x 106 kg total N yr–1. Little information was available to help determine loads and sources. Even less information related to urban homeowner lawn care practices, particularly fertilizer use and management, was available. Due to the imposition for the Neuse Estuary of a total maximum daily load by the USEPA, it becomes even more important to determine load contributions from the different sources of pollution (North Carolina Department of Environment and Natural Resources, 1999).
Although literature from turfgrass studies suggests that well-maintained lawns contribute small amounts of N into urban streams, turf comprises approximately 7% of the Neuse River basin land area and therefore may be a contributory factor (North Carolina Department of Environment and Natural Resources, 1997b). Knowing fertilizer use habits of homeowners is important to assess potential N nonpoint-source losses from urban areas. This study was conducted to address the data gaps associated with turf fertilization and cultural practices. A door-to-door lawn care survey was conducted in five communities, primarily in the Neuse River basin, to better define residential fertilizer and water use behavior. The objectives of this study were to (i) characterize fertilizer, pesticide, and water use in selected urban North Carolina areas, (ii) determine if uses differed due to community demographics, and (iii) use the information to direct lawn care education programs.
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METHODS |
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TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONCONCLUSIONSREFERENCES |
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Cary is located in the Piedmont region of the Neuse River basin. It is in close proximity to the Research Triangle Park, an international center for research and development of computers, pharmaceuticals, and agricultural chemicals, providing Cary with the highest growth rate and median yearly income (Town of Cary, personal communication, 1997). Table 1 presents the total population, growth rate, and median yearly income for Cary and the other communities. In Goldsboro, a community in the middle Coastal Plain, Seymour Johnson Air Force Base provides much of the economic foundation and population of the city (Wayne County Chamber of Commerce, personal communication, 1998). Kinston is located in the middle Coastal Plain, approximately 25 miles east of Goldsboro. Although it has prospered in years past from agriculture, it is presently losing population (Town of Kinston, personal communication, 1998). The most eastern city in the Neuse River basin is New Bern, located where the Neuse River widens to form the estuary in the flat topography of the Coastal Plains. Much of the growth of New Bern is due to retirees from out-of-state locating in the New Bern area (City of New Bern, personal communication, 1998). The fifth community is Greenville, which is one of two major towns located in the Tar–Pamlico River basin. The population in Greenville is primarily due to a major North Carolina university (East Carolina University) and major medical center (Town of Greenville, personal communication, 1998).
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We found turf area by determining the front pervious area (the area not covered by pavement or the house). We calculated front pervious area by pacing its length and width. An estimate was then made of the percentage of turfgrass within the pervious area. Backyard turfgrass area was assessed by asking the survey participants about the size of their backyard turf area relative to their front turf area (Fig. 2). The backyard estimation technique was used to reduce the time it took to survey and to avoid disturbing the participant. The two turfgrass areas were then summed for the total turfgrass area.
Sample Size and Data Collection
For a given community, the intended sample size design was 1% of the total household population of each community. Due primarily to differences in growth characteristics and willingness of volunteers, the following sample sizes were attained: Cary, 1% (n = 300); Goldsboro, 0.4% (n = 86); Kinston, 1.2% (n = 130); New Bern, 0.7% (n = 66); and Greenville, 0.5% (n = 130). The lower sampling rate in Goldsboro is somewhat deceptive in that the intent was to sample only in the Stoney Creek Watershed area of Goldsboro in support of an ongoing watershed study. The actual sample was acquired by randomly selecting subdivisions and 10 households per subdivision. Less than 1% of the households selected refused to be surveyed.
Corollary information (average tax valuation, average lot size, and average age of the house) was obtained for each subdivision from town records. Tax valuation was selected as a surrogate for income level. Low-income level is defined as a tax valuation of 
$125000, whereas medium income tax level has a tax valuation between $126000 and $174000 and high valuation is 
$175000. Tax valuation information by subdivision sampled was not available for the New Bern and Goldsboro locations. Results were analyzed by the analysis of variance technique using the Statistical Analysis System (SAS Institute, 1998).
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RESULTS |
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TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONCONCLUSIONSREFERENCES |
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More than one-half of urban homeowners surveyed across all communities use fertilizer on turf (Table 2). A number of households (16–43%) used lawn care services for fertilization, although this is highly variable by community. Cary, which has the highest median income, used lawn care companies with the greatest frequency. Fertilization was based on soil testing for only 20% of the households, although New Bern had a slightly higher rate of 35% (Table 2). Soil test reports recommend phosphorus (P) and potassium fertilization rates based on the soil test value for these two nutrients. Nitrogen fertilizer recommendations, however, are simply based on the predominant grass type. Cary, Goldsboro, and Greenville had approximately the same number of fertilizer applications per year (1.5), whereas the average number of fertilizer applications per year in New Bern was 3.0. More than one-half (53%) of all households surveyed (exclusive of Cary that was not sampled for this question) recycle their clippings (Table 2).
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Results from the survey indicate that for fescue, the majority of the fertilization is occurring in the late winter and early spring, February through April (Fig. 3) . Fescue fertilization should occur in September, November, and February. Most homeowners were only applying their spring applications to fescue. Timing of fertilizer applications to the warm-season grasses (zoysiagrass [Zoysia japonica Steud.], common bermudagrass [Cynodon dactylon (L.) Pers.], and centipedegrass) by homeowners occurred primarily in the spring (March and April) and the fall (September, October, and November), rather than in the summer months (May, June, July and August) (Fig. 3). Lawn care providers also tended to fertilize during the wrong season for warm-season grasses (Fig. 3). Inappropriately timed applications are being made to both cool- and warm-season grasses during periods of low growth or dormancy, thus reducing the efficiency of fertilizer use.
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15% N (Fig. 4)
. More than 30% of fertilizer use by residents in Cary and Greenville consisted of a high analysis N fertilizer (>15% N). High analysis N fertilizers are appropriate for tall fescue and at rates of 56 kg N ha–1 are easy to uniformly apply, but a uniform application of one-half of this rate, as needed for centipedegrass in Greenville, would be difficult to achieve.
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Most household residents (53%) used instructions on the bag and either grass type and/or lawn area to guide them on fertilizer application rates. Grass area or grass type was used by 21% of households to determine fertilizer rate. Eleven percent of the respondents used soil tests to guide their fertilizer application rates. We were unable to discern any fertilizer application criteria for about 15% of the residents.
Most respondents use either drop or spinner spreaders (77%) or their hands (18%) to distribute fertilizer. On average, 52% of households blew or swept fertilizers off driveways and other impervious surfaces. Residents in Cary had the lowest rate of removing fertilizer (41%), while residents in Greenville, New Bern, and Goldsboro had the highest rate (approximately 67%).
Water Use
Water use is an important consideration because it significantly influences leaching of mobile nutrients such as NO3–N. The overall average of residents who water during dry periods was 67%. Households in New Bern were more likely to water than households in the other communities (Table 3). Watering frequency, the number of times per week that residents watered, was greater in Greenville and Goldsboro than the other communities, although there was no significant difference (P < 0.0001) among the communities in their watering frequency. The range in watering frequency was from 0.5 to 7 times per week.
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Kinston has the largest number of residents that use hand sprinklers (25%) whereas hand watering is infrequent in the other communities. New Bern has the highest use of fixed irrigation systems (36%), while Greenville, Cary, and Goldsboro have a similar percentage of fixed sprinklers (approximately 15%). The fixed sprinkler systems may explain why New Bern had the greatest percentage of residents who water and Kinston had the lowest percentage of people who water.
Pesticide Use
The results for this section do not include responses from Cary residents since pesticide use questions were not included in the Cary survey. About 60% of all households use pesticides, with the greatest frequency in Greenville and the lowest in Kinston (Table 4). Typically, more residents use pesticides to treat weeds than either insects or diseases (Table 4). Plant diseases are the least likely problem treated by pesticides.
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Respondents were also asked what safety precautions are taken when applying pesticides. In general, reading the label was cited most frequently, followed by wearing protective clothing. Spot treating and pest identification tied as the third most cited precautions. The least cited precaution was selection of the safest pesticide.
Respondents were asked if they knew how to calibrate their equipment, to which 82% responded positively. Most respondents (78%) also said they calibrated before applying pesticides. In most communities the number of people who knew how to calibrate was greater than the number who actually calibrated. We assume that individuals who say they know how to calibrate are reading labels and following instructions rather than actually calibrating spreaders or sprayers.
Homeowners obtain lawn care advice as often from North Carolina Cooperative Extension as they do from retail outlets (Table 5). Advice is also sought from neighbors, but less frequently than from retail outlets or extension. On average, 77% of the residents surveyed had heard of the North Carolina Cooperative Extension Service.
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONCONCLUSIONSREFERENCES |
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Although the pesticide portion of the present survey was generic and of secondary interest, general trends were observed. Pesticide use was widespread in all communities (60% of homeowners) with herbicides being the predominant pesticide. Consumers appeared to be using pesticides correctly by using the designated application rates, calibrating equipment, reading labels, wearing protective clothing, and selectively treating affected areas. The most frequent concern that users have is danger to the health their family or pets.
Water use is definitely driven by lack of rainfall in all communities. Using average length of watering and watering frequency to determine the total amount of time that lawns are watered on a weekly basis, residents with moveable sprinklers watered approximately 2 h per week while residents with fixed sprinklers watered about 1 h per week. Although there was no way to ascertain the rate or amount of water application directly, based on the survey results alone, it appears that residents with fixed sprinklers were no more likely to use water than residents with moveable sprinklers.
The survey instrument did not collect data on actual rates of water use. Since inappropriate watering can increase N losses, it is critical to obtain reliable water use information. The Town of Cary compared metered water used between households with different sprinkler types (Town of Cary, personal communication, 1998). Residents who used moveable sprinklers water at about half the rate (2.3 x 105 L mo–1) as residents who used fixed sprinkler systems (4.2 x 105 L mo–1) (R2 = 0.99). The water use records indicated that significant differences in water use occur in a few neighborhoods that have installed irrigation systems. Based on these additional data, it appears that increased water usage may occur under installed irrigation systems thus increasing the chances of N leaching.
The need for soil testing by homeowners as well as landscape professionals was also evident. Although soil testing is unnecessary for N fertilization considerations, it is important to have optimum fertility as related to pH and nutrient levels so grass can efficiently utilize N. In some areas P losses are of greater concern than N, which is why we wanted to capture urban soil testing rates. The low rate of soil testing by homeowners in all communities demonstrates the need to stress soil testing, both to individuals as well as lawn care companies. (No lawn care companies that we interviewed soil-tested on a routine basis.) Initial soil testing of lawns in Cary found that the majority of the lawns did not need additional P. Without soil testing, homeowners will continue to add unnecessary P fertilizers and may have very low N use efficiency in lawns where fertility is otherwise not optimum.
Any fertilizer that lands on hard surfaces is subject to direct discharge into surface waters via stormwater systems. Only 52% of homeowners clean impervious surfaces after fertilization. Removing fertilizer inadvertently applied to impervious surfaces would decrease direct fertilizer discharge to surface waters and greatly reduce fertilizer pollution in urban areas.
The average urban–suburban lawn area from our survey is 0.1 ha or 1000 m2. The average lawn size collected in the aforementioned North Carolina Department of Agriculture and Consumer Services' statewide turf survey was 0.2 ha, about twice the size of lawns in our survey (Kneas and Smith, 2001). Their survey averaged both urban and rural residents, so it is not surprising that the average lawn size was lower in our survey where our residents tend to reside in denser suburban areas.
Approximately 70% of all homeowners in these communities apply N fertilizer (compared with the statewide average of 50%), with its use in most communities being slightly higher than the recommended levels for the types of grass grown. Since approximately 50% of homeowners recycle their grass clippings without giving N credits, this increases overapplication of N. Grass clippings can act as a continuous fertilizer source, and thus N fertilizer rates can be reduced as much as 30% (Osmond and Bruneau, 1999) to 50% (Heckman, 2001) when clippings are recycled. Commercial applicators generally applied more fertilizer than residents.
There appears to be evidence of overfertilization in the centipedegrass growing areas, since fertilizer N inputs were as much as 200% greater than recommended rates. This overapplication of 200% assumes a centipedegrass lawn, with the highest average rate of fertilization (56 kg N ha–1), and recycling of all lawn clippings. Overfertilization also potentially exists in the Piedmont where lawn care service is used and lawn clippings are left on the turf surface. Although turf is generally highly efficient in utilizing applied fertilizer N (Petrovic, 1990), potential exists for unused portions of applied N to move off-site in the sandy soil of the Coastal Plains region. Jacobs and Gilliam (1985) estimates that 95% of N losses from fertilized areas occur through subsurface flow of shallow ground water containing NO3–N.
Additional concerns of fertilizer use must also consider timing of N applications due to the differences in seasonal uptake of N relative to turf type. The recommendation for tall fescue, the predominant grass type in Cary, is an application of 156 kg N ha–1 split equally over three applications (normally occurring in September, November, and February). The spring application was generally made at the correct time, but fall applications were negligible. In the Coastal Plain, where centipedegrass occupies at least half of the turf area, a single N application is recommended, normally in June. Centipedegrass, along with the other warm-season grasses, was receiving fertilizer more often at the inappropriate times (spring and fall) than the correct times. This probably reduces fertilizer use efficiency, as well as turf health. Fertilizer application timing must be stressed more in our outreach programs.
The number of applications and types of fertilizer used were often not matched to the specifics of the area. We need to focus more education on fertilizer distributors. Homeowners in Greenville, where the predominant grasses were centipedegrass or centipede mixtures (centipedegrass mixed with other grass species), frequently used high N analysis fertilizers. Because of the low N requirements of centipedegrass, these high N analyses were inappropriate and probably added to the excess N application rates in Greenville. Retail outlets in Greenville should be encouraged to carry mostly low N analysis fertilizer to match the needs of centipedegrass. More educational effort needs to focus on selection of proper fertilizer grades.
The total amount of fertilizer use was greatest in Cary. Total N fertilizer use in Cary was 7 times greater than in Kinston, 5 times greater than in New Bern, and 1.6 times greater than in Greenville (Table 6). The greater total N use in Cary is due to the higher N fertilizer rates needed to fertilize tall fescue, the largest proportion of the population that applied fertilizer, and the greatest number of households. The overall use of fertilizer in Cary would have been higher except that average grass area was smaller than any other community. Grass type, town size, and intangible factors, such as owning or renting a house, rather than absolute income, confound fertilizer use patterns.
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CONCLUSIONS |
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TOPABSTRACTINTRODUCTIONMETHODSRESULTSDISCUSSIONCONCLUSIONSREFERENCES |
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To determine total N application to urban turf, we first had to determine the amount of urban land use area for the entire state of North Carolina. We obtained land use data from the North Carolina Center for Geographic Information and Analysis. Urban area comprises 286508 ha with 175230 ha being high-density development and the remainder, 111278 ha, being low-density development.
Not all urban areas are pervious nor is all the pervious area in turf. We assumed that 50% of the total urban area (143254 ha) is turf. Based on our survey, we found that 70% of the turf was fertilized, so we assumed a 70% fertilization rate or 100278 ha of fertilized turf. Because we had a range in N fertilizer use (0–155 kg N ha–1 year), we assumed an average N use of 111 kg N ha–1 yr–1. This translates to a total application rate of 11.1 x 106 kg N yr–1 on urban turf in North Carolina.
Golf courses comprise another major turf area. During the debate on the sources of N into the Neuse River, golf courses were often cited as major contributors. A survey of the majority of the golf courses in the Neuse River basin was conducted (Osmond et al., 1999). Total N applied to all golf courses in North Carolina was determined to be approximately 2.6 x 106 kg N yr–1, based on an estimated 550 golf courses with an assumed average size of about 60 ha per course. (Osmond et al., 1999). The average fertilizer N use is 77.6 kg N ha–1 yr–1 on each of the 60 ha. In reality some parts of the course are not fertilized while other parts are fertilized intensively.
In addition we determined N use on roadside turf in North Carolina. There are nearly 1.6 x 106 highway road kilometers within North Carolina. Not all these road kilometers are fertilized every year. Using numbers provided by the North Carolina Department of Transportation on the number of road kilometers fertilized annually, we estimated 30000 km with approximately 6 m of roadside and/or median width, or 18000 ha. The average N fertilization rate of roadside turf is 8.9 kg N ha–1 yr–1 or 1.6 x 105 kg N yr–1.
Based on our statewide analysis, 13.9 x 106 kg N are applied to residential turf, golf courses, and roadsides each year in North Carolina. The accuracy of the original land use data and the assumptions on N fertilizer rates on turf affect the veracity of the estimates. These data, however, allow us to begin to estimate the relative proportions of fertilizer use for turf as compared with agricultural crops. Approximately 30.0 x 106 kg N yr–1 are applied to agricultural crops in the Neuse River basin alone. This assumes there is 4.9 x 105 agricultural ha in the Neuse River basin with an average N application rate of 56 kg N ha–1 yr–1. Thus there is two times as much fertilizer used on agricultural crops in one river basin than used on turf in the entire state of North Carolina. The rate of N application on a per hectare basis, however, is greater for turf than agricultural crops.
In conclusion, the information collected in this door-to-door lawn care survey has allowed us to establish a targeted educational program to urban audiences. Five areas where the data suggested turf care improvements by homeowners are needed were as follows: timing of fertilizer applications, cleaning fertilizers from impervious surfaces, N fertilizer rates (especially for centipedegrass), selection of appropriate fertilizer analyses, and soil testing. There was little overfertilization of fescue by homeowners, although in the one community where we obtained data from lawn care industry, it appeared that there is overapplication of N fertilizer by lawn care providers. Centipedegrass was overfertilized more than was fescue. This appeared to be a function of mismatched fertilizers and grass types. Fertilizer distributors should match the fertilizer analyses they sell to the needs of the grass types. Fertilizer on impervious surfaces is of considerable concern since fertilizers are readily washed into storm drains during rainstorms and this drainage leads directly to streams. Educational messages have been focused on these areas. As an example, a 30-min television public-service stormwater announcement has just been released that, along with other topics, discusses managing fertilizers in urban areas.
Water use is currently being addressed through local ordinances. Due to the four-year drought (1998–2002), most communities throughout North Carolina are either restricting watering year round (such as Cary) or during summer drought episodes (summer 2002). With decreased watering comes a reduction in potential runoff. However, with drought, homeowners also need to be adjusting N fertilizer rates.
In addition to using the data to determine relative proportions of fertilizer used by the different land users, this survey has provided information for other uses. Recently the turf fertilization rate data were incorporated into the Sparrow model that is being used by U.S. Geologic Survey to partition N and P sources, in an attempt to meet some of the requirements for the Neuse River total maximum daily load requirement. As other total maximum daily loads are developed, this urban fertilizer use information will be of use to both the research and regulatory communities. For example, satellite data can be used both at the state as well as the river basin scale and would allow for basin-by-basin estimates of N fertilizer use on residential turf.
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ACKNOWLEDGMENTS |
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REFERENCES |
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