From the July 2016 issue of GCM magazine:
New study quantifies nutrient use and management on U.S. golf courses
Golf courses in the U.S. significantly reduced nutrient use between 2006 and 2014, though improvements can still be made through reductions in fertilized turf acreage, decreases in winter overseeding, and greater use of precision fertilizer applications.
In 2011, Pinehurst No. 2 completed an extensive restoration that involved incorporating numerous na-tive plants and removing more than 40 acres of bermudagrass turf.
Photo courtesy of USGA
Wendy Gelernter, Ph.D., and Larry Stowell, Ph.D.
The second phase of the Golf Course Environmental Profile was conducted by GCSAA through the Environmental Institute for Golf and funded by the United States Golf Association.
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Between 2006 and 2014, U.S. golf courses significantly decreased their nutrient use, with annual reductions of 34% for nitrogen, 53% for phosphate and 42% for potash. As a result, they have minimized the potential for runoff pollution from fertilizer applications, saved money and improved the precision of their nutrient applications. But how, exactly, was this change brought about? Where did the greatest decreases occur? And which agronomic practices, regulatory forces and economic factors were involved?
In this article, we will address these questions by summarizing the data from national surveys that were conducted by GCSAA to characterize nutrient use and conservation trends on U.S. golf courses in 2006 and 2014.
Nutrient use and the Golf Course Environmental Profile
In 2006, GCSAA and the Environmental Institute for Golf (EIFG) initiated a project to conduct a series of five surveys to document water use, fertilizer use, pest management practices, energy use, environmental stewardship and property profiles. Known as the “Golf Course Environmental Profile,” the survey results provided a baseline of information for use in the management of golf facilities, as well as an important tool for communicating within the golf course industry and with regulators, legislators and the general public. Results were published in scientific journals (1-5) and on the EIFG website (www.gcsaa.org/environment/environmental-profile/golf-course-environmental-profile-overview).
Figure 1. Distribution of 2015 survey responses across the survey’s seven agronomic regions.
In fall 2014, the second phase of the Golf Course Environmental Profile began, with a follow-up set of surveys that mirror the previous series. The surveys are being conducted by GCSAA through EIFG and funded by the United States Golf Association (USGA). Nutrient use and management is the second survey to be released in the second phase.
How it was done
An initial email invitation, which included a link to an online survey, was sent to 13,723 U.S. golf courses in March 2015, followed by three email reminders. A total of 1,529 completed surveys were received, which represents a 9.9% response. Although this response rate is somewhat lower than the 16.1% from the 2006 survey, it is still considered a strong response.
PACE Turf and the National Golf Foundation (NGF) were contracted to develop and implement the survey, as well as to analyze, summarize and publish reports on the data.
To gain insights into survey data, respondents were stratified by agronomic region (Figure 1), as well as by golf course type, number of holes and green fees.
Figure 2. Changes in total nutrient use for nitrogen, phosphate and potash: 2006 vs. 2014.
This report incorporates, for the first time, specific information on each survey respondent’s climate and weather, thus providing greater insight into nutrient use patterns. Each respondent’s ZIP code was matched to 30-year average air temperature and precipitation data from the PRISM Climate Group at Oregon State University (www.prism.oregonstate.edu).
Trends in national nutrient use
U.S. golf courses have decreased their nutrient use since 2006, with annual reductions of 34% (30,970 tons) for nitrogen, 53% (17,867 tons) for phosphate and 42% (37,419 tons) for potash (Figure 2). All seven of the nation’s agronomic regions participated in this trend (Table 1).
Three major factors contributed to decreases in nutrient use (Figure 3):
- reductions in nutrient use rates (Table 2)
- reductions in number of turf acres fertilized (Table 3)
- reductions in number of golf facilities (Table 4)
Table 1. Projected regional and national nutrient use (tons), 2006 vs. 2014.
Reduced rates and acreages were responsible for approximately 90% of the observed nutrient use savings (Figure 3). Facility closures were responsible for approximately 9% of the observed decrease in nutrient use (Figure 3).
Reducing nutrient use rates
Nitrogen use rates were reduced by 13% to 30% between 2006 and 2014, depending on the region (Table 2), resulting in savings of an estimated 15,226 tons of nitrogen per year (Figure 3). Rates were highest on greens, and consecutively lower on tees, practice areas, fairways, grounds and roughs (Figure 4). Nitrogen use rates were correlated with the length of the growing season, with the highest rates occurring in regions with the longest growing seasons (Table 2).
Phosphate use rates were reduced by 39% to 75%, depending on the region (Table 2), resulting in savings of an estimated 4,901 tons of phosphate per year (Figure 3). Increases in government restrictions on the use of phosphate (Table 5) are an important factor in this large decrease. Phosphate use rates were highest on greens, and consecutively lower on tees and practice areas, fairways, grounds and roughs (Figure 4).
Potash use rates were reduced by 33% to 57%, depending on the region (Table 2), resulting in savings of an estimated 19,740 tons of potash per year (Figure 3). Potash use rates were highest on greens, and consecutively lower on tees, practice areas, fairways, grounds and roughs (Figure 4).
Figure 3. Factors contributing to decreased nutrient use, 2006-2014. Reductions in nutrient rates and acreages were responsible for over 90% of the decreases in total nutrient use since 2006.
An estimated 4,166 — or 27% of — U.S. golf courses reduced fertilized acreage between 2009 and 2014, resulting in reductions in acres fertilized with nitrogen (16%), phosphate (46%) and potash (22%) (Table 3).
The amount of nutrients saved annually as a result of acreage reduction was estimated to be 12,224 tons of nitrogen, 11,851 tons of phosphate and 14,489 tons of potash (Table 3, Figure 3).
Reductions in number of golf facilities
Fertilizer use was further reduced by a net decrease of 618 golf facilities between 2006 and 2014 (Table 4). All regions except the Upper West/Mountain had a drop in the number of facilities over this time period. The estimated annual nutrient savings as a result of decreased facility numbers were 3,519 tons of nitrogen, 1,115 tons of phosphate and 3,190 tons of potash — or about 9% of the nation’s total decrease in nutrient use (Figure 3).
Table 2. Nutrient use rates in 2006 vs. 2014 for 18-hole golf courses, and the climatic factors that affect them. For each 2006 vs. 2014 comparison, values in bold type with the lower value followed by an asterisk indicate that there was a significant difference between the 2006 and 2014 values (P ≤ 0.10). Reading down each column, values followed by the same letter are not significantly different at the 90% confidence level. All values shown are medians.
The reductions in nutrient use rate and acreage that have been described came about through adoption of conservation practices (Figure 5), which were responsible for approximately 90% of the nutrient savings. Adoption of almost all conservation practices has increased since 2006. The most commonly used of these practices include:
- avoiding overseeding
- fertilizing based on soil test results
- returning clippings
- precision fertilizer application
Table 3. Reductions in fertilized acreages from 2006 to 2014, and the estimated nutrient savings that resulted.
Role of overseeding in nutrient use
Reductions in winter overseeding of warm-season turf contributed to decreased nutrient use, with more than 40% of respondents in the Southwest and Southeast regions reporting that they had either stopped overseeding or reduced overseeding. Avoiding overseeding resulted in rate reductions of up to 30% (Figure 6).
Surprising results on soil testing
When asked what practices were used to reduce reliance on fertilizers, the most common response was the use of soil tests to determine fertilization rates (Figure 5). Yet surprisingly, the survey shows that golf courses that conduct soil tests tend to use higher rates of nutrients than those that do not use soil tests (Table 6). The reason for this unexpected result may be that some current turf soil guidelines target nutrient levels higher than those required for acceptable turf growth. This issue will be discussed further in the “Soil guidelines” section below.
Nutrient use decision-making
Table 4. Changes in nutrient use resulting from reductions in the number of golf facilities, 2006-2014.
Soil guidelines. Superintendents have increased their reliance on university and manufacturer recommendations to develop their nutrient management programs. However, soil nutrient guidelines developed in the past tended to target higher levels of nutrients than may be required. Recent research has identified soil nutrient guidelines (such as the Minimum Levels for Sustainable Nutrition [MLSN]) that, although targeting lower use patterns than those previously identified, do not appear to sacrifice turf health or playability (7). Reliance on these more current, science-based recommendations should contribute to further nutrient use reductions in the future.
Regulatory restrictions. Restrictions on the use of phosphate far outstrip any other regulation cited by survey respondents (Table 5). Where these restrictions occurred, rates of phosphate use dropped significantly (Figure 7).
Economics. As described above, the net decrease of 618 golf facilities since 2006, which was largely triggered by the Great Recession, has driven about 9% of the nutrient use reductions reported here (Figure 3). In addition, survey respondents reported that fertilizer cost has grown in importance as a factor in nutrient use decisions (Table 7). This observation is further supported by the U.S. Department of Agriculture’s Economic Research Service, which found that the average cost of phosphate- and potassium-based fertilizers increased by more than 100% between 2006 and 2013 (the last year that data was collected), and that the cost of nitrogen-based fertilizers increased by more than 60% (6).
Figure 4. Median U.S. nutrient use rates on each feature of 18-hole golf courses, 2014.
Superintendents reported a wide variety of influences on nutrient program decision-making (Table 7). Three of these factors — soil guideline recommendations, regulatory restrictions and economics — deserve further discussion.
Table 5. Types of federal, state, local government or tribal authority restrictions on fertilizer applications reported by 18-hole facilities. Values within each two-column row that are followed by the same letter are not significantly different at the 90% confidence level.
Nutrient ratios
Since 2006, a beneficial change has occurred in the relative ratios of applied nitrogen, phosphate and potash. As a result, lower proportions of phosphate and potash were used in 2014 than in 2006 (Table 8). This change is primarily due to regulatory pressures that have caused both fertilizer manufacturers and golf course superintendents to shift toward lower use rates, particularly of phosphate. See “Interpreting fertilizer application ratios” for more information.
Trends in regional nutrient use
Nutrient use varies dramatically among the nation’s seven agronomic regions, both in total amount used (Table 1) and in rates used (Table 2).
Climate and its impact on the length of the growing season is the most important contributor to regional differences in nutrient use. For example, the lowest nutrient rates occur in the cool climates of the Northeast and North Central regions, while the highest rates occur in the Southeast and Southwest regions, which have the highest average temperatures (Table 2).
The number of facilities per region also contributes to regional differences in total nutrient use. For example, regions with many facilities (such as the North Central region) have higher total nutrient use, regardless of how low their nutrient use rates may be, while regions with fewer facilities (Pacific, Southwest) have lower total nutrient use, even if nutrient use rates are relatively high (Tables 1, 4).
Figure 5. Nutrient conservation practices that resulted in nutrient savings from 2006 to 2014.
Notable regional trends include:
- Reduced total nutrient use. The greatest percentage decreases occurred in total nitrogen use in the Southeast region, total phosphate use in the North Central and Northeast regions, and total potash use in the Southwest and Southeast regions (Table 1).
- Reduced nutrient use rates. The greatest percentage decreases occurred in nitrogen rate in the Southeast region, in phosphate rate in the North Central and Transition regions, and in potash in the Upper West/Mountain region (Table 2).
- Reduced number of fertilized acres. The greatest percentage of decreases in number of acres fertilized occurred with nitrogen in the Southwest region, with phosphate in the North Central and Northeast regions, and with potash in the Southwest region (Table 3).
Variation in nutrient use was also significant within each agronomic region, particularly in the Pacific and Southwest regions, which have the most diverse climates.
Nitrogen sources, amendments and supplements
Organic fertilizers. Organic fertilizers (materials derived from either plant or animal products containing one or more elements — other than carbon, hydrogen or oxygen — that are essential for plant growth) were used on 64% of all golf courses in 2014, consistent with use in 2006. Organic products based on animal waste were used by 65% of courses that apply organic fertilizers, making this the most common source, followed by local sewage sludge (39%), crop products such as soybean or corn meal (14%), and food waste, including composted products (13%).
Figure 6. Increased nutrient use rates caused by overseeding in the Southwest, Southeast and Transition regions. All values shown are medians. Values within each two-column row that are followed by the same letter are not significantly different at the 90% confidence level.
Slow-release vs. quick-release nitrogen. In 2014, two-thirds of all nitrogen was applied as slow-release formulations and one-third as quick-release formulations, representing little change in use patterns since 2006. The popularity of slow-release (water-insoluble) products is based on convenience (given that fewer applications are required), decreased risk of foliage burn, and decreased likelihood of leaching into groundwater when used properly. The cost of slow-release products is higher, however, which may explain their flat adoption rate during the years of the Great Recession.
Amendments and supplements. In 2014, the most commonly applied products included humic materials, amino acids/proteins, gypsum and biostimulants. Since 2006, the greatest increases in adoption have occurred for sulfur, compost teas, calcium chloride, microbial inoculants and gypsum.
Fertilizer application and storage
Calibration. Between 2006 and 2014, very little change occurred in the frequency of calibrating equipment before use. Applications were calibrated more frequently for fairways (71% of the time) and roughs (77% of the time) than for greens (67% of the time) or tees (68% of the time). The frequent calibration of applications to fairways and roughs may be due to the much larger number of fertilized acreages associated with those areas of the golf course and, therefore, greater economic and environmental incentives for accuracy.
Application frequency. As may be expected, regions with the longest growing season and highest rainfall, such as the Southeast, had the highest number of fertilizer applications per year, especially on greens, while cooler regions with fewer active turfgrass growing months had the lowest number of applications (Table 9). Greens received, by far, more fertilizer applications than any other golf course feature. This is to be expected, in part, because greens are the most heavily trafficked areas of a golf course and are, therefore, treated with higher rates of fertilizer, which should be dispensed in smaller doses to prevent growth surges.
Storage. Since 2006, there has been a 46% to 65% increase in the number of golf courses storing fertilizer in a facility designed for fertilizer storage that, at a minimum, has an impervious floor, a cover, ventilation, security (locked with access restricted), and containment features to prevent loss to the environment and/or contamination from runoff.
Conclusions and recommendations
- Significant reductions in nutrient use have occurred over the past eight years because of a combination of voluntary conservation practices, regulatory restrictions, golf facility closures and economically driven decisions.
- The dramatic downward shifts in nutrient use rates between 2006 and 2014 were made without apparent declines in turf quality and playability. This could be due to storage of excess nutrients in the soil. Therefore, it is expected that, as the soil’s nutrient reservoirs are depleted by turf growth, fertilizer use will not continue to decline at the same rate as documented here, and may even increase slightly to meet plant requirements.
- Management practices such as reductions in overall and/or fertilized turf acreage, decreased winter overseeding and precision fertilizer applications will lead to further nutrient conservation, and will have the added benefit of supporting water conservation efforts.
- Soil test results should be interpreted using the most current, region-appropriate soil nutrient and plant requirement guidelines, in order to minimize environmental impact and unnecessarily high fertilizer application rates.
- There is still room for greater adoption of equipment calibration techniques in order to ensure fertilizer is not being applied at either too high or too low of a rate.
Figure 7. Effect of federal, state, tribal and/or local restrictions on nutrient use rates on 18-hole golf courses in 2014. All values shown are medians. The asterisk indicates there was a significant difference between 2006 and 2014 at the 90% confidence level.
- While the number of golf courses with specially designated fertilizer storage facilities has increased, there is still room for improvement in the use of these facilities.
Funding
The second phase of the Golf Course Environmental Profile was conducted by GCSAA through the Environmental Institute for Golf and funded by the United States Golf Association.
Literature cited
- Lyman, G.T., M.E. Johnson, G.A. Stacey and C.D. Brown. 2012a. Golf course environmental profile measures pesticide use practices and trends. Applied Turfgrass Science doi:10.1094/ATS-2012-1220-01-RS
- Lyman, G.T., M.E. Johnson, G.A. Stacey and C.D. Brown. 2012b. Golf course environmental profile measures energy use and energy management practices. Applied Turfgrass Science doi:10.1094/ATS-2012-0228-01-RS
- Lyman, G.T., C.S. Throssell, M.E. Johnson, G.A. Stacey and C.D. Brown. 2007. Golf course profile describes turfgrass, landscape and environmental stewardship features. Applied Turfgrass Science doi:10.1094/ATS-2007-1107-01-RS
- Throssell, C.S., G.T. Lyman, M.E. Johnson, G.A. Stacey and C.D. Brown. 2009a. Golf course environmental profile measures water use, source, cost, quality, and management and conservation strategies. Applied Turfgrass Science doi:10.1094/ATS-2009-0129-01-RS
- Throssell, C.S., G.T. Lyman, M.E. Johnson, G.A. Stacey and C.D. Brown. 2009b. Golf course environmental profile measures nutrient use and management and fertilizer restrictions, storage and equipment calibration. Applied Turfgrass Science doi:10.1094/ATS-2009-1203-01-RS
- USDA Economic Research Service, 2013. Average U.S. farm prices of selected fertilizers, 1960-2013. (www.ers.usda.gov/data-products/fertilizer-use-and-price.aspx#26727). Accessed May 17, 2016.
- Woods, M.S., L. Stowell and W. Gelernter. 2014. Just what the grass requires: Using minimum levels for sustainable nutrition. Golf Course Management 82(1):132-138.
Wendy Gelernter, Ph.D. (and www.paceturf.org), and Larry Stowell, Ph.D., are the principals of PACE Turf, San Diego.
Table 6. Influence of soil testing on nutrient use for a typical 18-hole golf course in 2014. For each comparison, values in the same row that are followed by the same letter indicate that they were not significantly different at the 90% confidence level.
*Not asked in 2006.
Table 7. Factors involved in nutrient use decisions. Respondents rated factors on a 1-5 scale, where 1 = not important at all, and 5 = extremely important. Values shown represent the mean score for all respondents. Values within each two-column row that are followed by the same letter are not significantly different at the 90% confidence level.
Significant change in the proportion of nitrogen to other nutrients in 2006 vs. 2014 at a 90% confidence level.
**Significant change in the proportion of potash to other nutrients in 2006 vs. 2014 at a 90% confidence level.
Table 8. Fertilizer application ratios for nitrogen, phosphate and potash in 2006 and 2014. Data is based on median nutrient use rates for 18-hole golf courses. Median values shown were computed based on nutrient ratios determined for each respondent.
Table 9. Number of fertilizer applications per year at 18-hole facilities. For each 2006 vs. 2014 comparison, values followed by the same letter are not significantly different at the 90% confidence level.