ii
EXECUTIVE SUMMARY
There has been much legislative, regulatory, and litigation activity in Florida lately regarding
protection of water resources from nutrient pollution. Nutrients can reach surface water resources via
ground water baseflow ‐ ‐ this is mostly just a pathway for nitrate‐nitrogen ‐ ‐ stormwater runoff, erosion,
and atmospheric deposition. The generic pollutant endpoints are eutrophication and algal blooms. The latter
is a component of eutrophication, but it can also be a harmful endpoint itself.
Causes of Eutrophication and Harmful Algal Blooms
The causes of surface water resource degradation in this context are total nitrogen (TN), total
phosphorus (TP), total suspended solids (TSS), and elevated temperatures. All parameters are important. The
undesirable progression toward eutrophication and algal blooms is limited by TN in some systems, and other
systems are limited by TP. TSS can be a vehicle to convey TP, and TSS can degrade lake and stream bottoms
via siltation. Multiple sources and activities cause the loading of these constituents to surface water
resources. Turf fertilization almost certainly contributes some of this pollutant load, but its contribution
relative to other sources does not appear to be high. Further, any turf fertilizer restrictions that ultimately
cause turf density to decrease will yield greater TSS (erosion), which can increase TP in runoff, as well as
decrease water clarity, i.e., light penetration to beneficial aquatic plants.
It is scientifically valid for ordinances, regulations, etc. to be based on all contributors to this water
quality problem. “Contributors” in this context indicate two categories: land users (e.g., turf managers), and
parameters ‐ ‐ TN, TP, TSS, and those factors that increase water temperature (e.g., paving). Thus a
comprehensive scientifically valid approach is needed, rather than an approach that has a very limited focus.
Apparently, one driving force behind the proposed Collier County ordinance is the Gordon River Extension
Total Maximum Daily Load (TMDL). Unfortunately, this TMDL is only based on TN, and it is possible that water
quality will not be significantly improved if the TMDL goal (lower TN) is achieved, but consideration is not
given for the other factors.
The Turf System
Well maintained turf is an excellent natural filter. It is often used as a stormwater BMP, and in
phytoremediation for contaminated soils (contaminant cleanup using plants). Its thatch layer, an organic mat,
is unique among other plant systems. More rainfall is required to generate runoff from turf than from any
other land cover except for densely wooded terrain. Many studies have been done that demonstrate
minimal TN, TP, and TSS losses from turf.
iii
The Proposed Collier County Ordinance
The proposed Collier County fertilizer ordinance addresses a variety of topics in each of its 15
sections. The science in this report forms the basis for commenting on four of the provisions in the draft
ordinance: timing of fertilizer applications; fertilizer‐free zones; fertilizer content; and fertilizer application
rates.
To our knowledge, more work has been done in Florida to create meaningful and feasible BMPs for
the turf/green industry than in any other state. The results of these efforts should be seriously considered in
the development of any relevant legislations/regulations. Fourteen specific BMP recommendations, one of
which references 16 other specific recommendations, are recommended for consideration by the Collier
County government. Most, but not all, of the recommendations contained herein are also contained within
the previous statewide BMP documents. The three main targets of these recommended BMPs are golf
courses, professional lawn care companies, and a combination of homeowners and their government.
Before any legislative or regulatory body places a significant burden on turf managers in this context,
it should ensure the burden it imposes is approximately proportional to the environmental impacts caused by
turf management. This determination should be based on valid science. Eutrophication and harmful algae
blooms have many potential causes, including paved surfaces, reduced tree cover, septic systems, wild and
domestic animal waste, various agricultural land uses, leaky sewer lines, erosion, atmospheric deposition,
etc., in addition to urban fertilizer use. It does not appear as if this comprehensive analysis has been done.
The timing requirement (section 5) does not appear to be scientifically valid. It prohibits fertilizer
application when the turf plants are actively growing. Imposition of a four‐month summer blackout period
may or may not yield a detectible amount of environmental improvement in the short term. In the long term
(two to four years), the concentrations of eroded sediments and TP in surface water bodies will likely
increase. The need for pesticides (herbicides, insecticides, and fungicides) will also likely increase. Thus there
could be overall adverse impacts to the aquatic system.
Sections 9 and 10, “Application Practices” and “Management of Grass Clippings…” are well written
and should be immediately implemented. Some concerns are expressed about two of the other provisions
regarding nitrogen and buffer zones.
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TABLE OF CONTENTS
EXECUTIVE SUMMARY .................................................................................................................................. ii I. INTRODUCTION AND PURPOSE ............................................................................................................ 1 A. Introduction ...................................................................................................................................... 1 B. Purpose ............................................................................................................................................. 2
II. NUTRIENT CRITERIA AND TMDLs: SCIENCE AND REGULATION ............................................................ 3 A. Nutrient Limits .................................................................................................................................. 3 1. EPA Nutrient Criteria ..................................................................................................................... 3 2. Collier County TMDLs .................................................................................................................... 3
B. The Scientific Bases for the Nutrient Limits ...................................................................................... 4 III. RELATIVE SOURCE CONTRIBUTION ................................................................................................... 7 A. Possible N, P, and Sediment Sources ................................................................................................ 8 B. Relative Source Contributions .......................................................................................................... 9 1. Example from the Wekiva River Basin .......................................................................................... 9 2. Examples from the Lake Trafford TMDL ..................................................................................... 10 3. Chesapeake Bay Example ............................................................................................................ 11 4. Summary ..................................................................................................................................... 12
IV. TP AND TN LOSS FROM TURF VIA RUNOFF AND LEACHATE ........................................................... 13 A. The Results of Two Comprehensive Metastudies and One Local Study ......................................... 13 B. Wekiva River Basin Study ................................................................................................................ 14 C. Turfgrass Hydrology ........................................................................................................................ 14 D. Edge‐of‐Field Runoff and Leaching Studies .................................................................................... 15 1. Runoff .......................................................................................................................................... 16 2. Leaching ...................................................................................................................................... 16
V. CONCLUSIONS AND RECOMMENDATIONS ......................................................................................... 17 A. The Collier County Proposed Ordinance ......................................................................................... 17 B. Recommended BMPs ...................................................................................................................... 18 1. Golf Courses ................................................................................................................................ 18 2. Professional Lawn Care Companies ............................................................................................ 18 3. Homeowners and County/Municipal Governments ................................................................... 19
REFERENCES ................................................................................................................................................ 20 Appendix A. TR‐55 Runoff Calculations and Rainfall Threshold Determinations for Collier County Turf A‐1 Appendix B. Golf Course Best Management Practice Checklist ................................................................ B‐1
LIST OF TABLES AND FIGURES
Table II‐1. Lake Trafford TMDL Load Allocations ................................................................................... 4 Table II‐2. Relationship Between Chlorophyll‐a and Various Parameters ............................................. 5 Table III‐1. Nonpoint Sources of TN, TP, and TSS .................................................................................... 8
Figure III‐1. Conceptual Analysis of Costs and Benefits ........................................................................... 7 Figure III‐2. Nitrate Loading in the Wekiva River Basin .......................................................................... 10 Figure III‐3a. Annual Average TP Loads (lbs/yr) from Different Land Use Types to Lake Trafford Over a 10‐Year Period ................................................................................................................. 10 Figure III‐3b. Annual Average TN Loads from Different Land Use Types to Lake Trafford over a 10‐yr Period .............................................................................................................................. 11 Figure III‐4. EPA‐Modeled Land Use Contributions to the Chesapeake Bay .......................................... 11
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I. INTRODUCTION AND PURPOSE
A. Introduction
Many of Florida’s surface water bodies are classified as “impaired” by the Florida Department of
Environmental Protection (DEP) and the US Environmental Protection Agency (EPA), pursuant to §303(d)
of the Clean Water Act (CWA). These classifications, as well as the desire to protect Florida’s water
resources, have triggered several legislative, regulatory, and litigative actions. Included among these are
the establishment of nutrient criteria by the EPA, establishment of Total Maximum Daily Loads (TMDLs*)
for specific water bodies and/or watersheds by the DEP, and the passage of legislation/ordinances at the
level of counties and cities, as follows.
EPA Nutrient Criteria. In response to a lawsuit, the EPA recently promulgated nutrient criteria for Florida
streams and lakes (US EPA, 2010a). The criteria for streams do not apply to southern Florida. The criteria
are concentration goals for total nitrogen (TN), total phosphorus (TP), and chlorophyll‐a. Certain aspects
of the scientific basis of these criteria are discussed in sections II(A) and (B) below.
Florida TMDLs. Two TMDLs have been recently established by the DEP. These TMDLs target
improvement of water quality in Lake Trafford (FDEP, 2008a) and the Gordon River Extension (FDEP,
2008b). The Gordon River Extension focuses only on TN limits as a mechanism to increase dissolved
oxygen (DO) and decrease chlorophyll‐a. (Low DO and high chlorophyll‐a are indicators of water quality
that is consistent with eutrophication and ‘blooms’ of harmful algae.) The Lake Trafford TMDL implicitly
recognizes the need to be more holistic, and thereby attempts to control multiple relevant parameters.
This holistic approach is discussed in greater depth in sections II(A and (B).
Proposed County and Local Ordinances. Sarasota and Lee Counties implemented fertilizer ordinances in
2007 and 2008, respectively. Several towns/cities, including Naples, have passed similar or identical
ordinances recently (2007‐2010). The State has also developed a model ordinance that is a minimum
base for county and local ordinances, “Model Ordinance for Florida‐Friendly Fertilizer Use on Urban
Landscapes” (2009).
* TMDLs = Total Maximum Daily Loads = calculations of the maximum amount of specified pollutants that water bodies can receive and still safely meet water quality standards.
2
Collier County proposed an ordinance similar to many aspects of the other ordinances in
January, 2011. Although our report takes a holistic approach to the regulatory science relevant to all
these recent actions, there is also a focus on the following key provisions of the draft Collier County
ordinance:
• timing of fertilizer applications;
• fertilizer‐free zones;
• fertilizer content; and
• fertilizer application rates.
The County is now soliciting public comments on this proposed ordinance. This report is being submitted
to the County as part of that process.
B. Purpose
The purpose of this report is to provide a unifying scientific perspective on the subject. An
overview of the underlying causes of eutrophication and algal blooms is offered in the context of their
chief indicators ‐ ‐ decreases in dissolved oxygen and increase in chlorophyll‐a. Key research relevant to
nutrient and sediment losses from turf is summarized. Comments on the proposed Collier County
ordinance are provided. Finally, a proactive environmental stewardship approach based mostly on
existing programs and documents is recommended.
3
II. NUTRIENT CRITERIA AND TMDLs: SCIENCE AND REGULATION
The purpose of this section is to demonstrate that water quality protection requires a careful
evaluation of several parameters. The Collier County ordinance tends to have a focus on nitrogen, as
well as on one particular kind of land use.
A. Nutrient Limits
1. EPA Nutrient Criteria
The EPA and the states typically propose ecoregional nutrient criteria that are different
for lakes and flowing waters. Nutrient criteria for streams have not yet been promulgated for
South Florida. The following limits are only presented as general background information. The
new nutrient criteria for streams throughout the rest of Florida vary from 0.67 mg TN/L to 1.87
mg TN/L, depending on the region of the State (US EPA 2010a). The new criteria range for TP is
0.06 mg/L to 0.49 mg/L. The stream criteria are based on the reference approach, which is the
general approach the DEP used for the Gordon River Extension TMDL (see below; FEDP, 2008b).
This reference approach was recently criticized as the least valid method to develop nutrient
criteria (NACWA, 2011).
The EPA’s nutrient criteria for Florida lakes range from 0.01 – 0.05 mg/L for TP and 0.51
– 1.27 mg/L for TN (US EPA, 2010a).
2. Collier County TMDLs
a. Lake Trafford
The goals of the Lake Trafford TMDL are TN = 1.09 mg/L, TP = 0.025 mg/L, chlorophyll‐a
= 0.01904 mg/L (19 μg/L), and trophic state index (TSI) = 56 (FDEP, 2008a). The TMDL load
allocations are presented in Table II‐1. TSS is not addressed, but it is a factor that should be
considered.
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Table II‐1. Lake Trafford TMDL Load Allocations*
Parameter Stormwater (% reduction)
LA (lbs/year)
TMDL (lbs/year)
Percent Reduction
TN 60 56,617 56,617 60 TP 77 3,348 3,348 77 *The load reductions of TN and TP will correct the impairments for nutrients, un‐ionized ammonia, and dissolved oxygen. The allowable loads as pounds/day are 155.1 lbs/day for TN, and 9.17 lbs/day for TP. Achieving a long‐term TSI of 56 results in an average Chl‐a concentration of 19.04 μg/L, TN of 1.09 mg/L, TP of 0.025 mg/L, and a TN/TP ratio of 44.
b. Gordon River Extension
This TMDL was based on the reference approach, analogous to the EPA approach for the
stream criteria listed in 1(a) above (FDEP, 2008b). The TMDL is listed as a simple concentration
goal for a single parameter, TN ‐ ‐ 0.74 mg/L. Note that this is lower than all TN goals presented
above, and that it does not consider other contributors to eutrophication (discussed below).
Apparently, this TMDL was a driving force behind the proposed Collier County ordinance.
B. The Scientific Bases for the Nutrient Limits
The end result of eutrophication of streams and lakes is a decrease in dissolved oxygen [DO]
caused by an increase and decomposition of algae. The State standard for DO is 5.0 mg/L. The EPA’s
goals for chlorophyll‐a, an indicator of algae, are 6 μg/L and 20 μg/L, depending on the water body.
Decreases in DO and increases in chlorophyll‐a are due to complex processes, and are not well predicted
by TN alone. This important point is discussed further in this section.
The goal of the EPA stream nutrient criteria is the upper 90th percentile of the TN and TP
concentrations for most regions in northern and central Florida. The ultimate concern is excessive
growth of algae and undesirable aquatic plants. The goal of the EPA lake criteria is more quantitatively
focused on chlorophyll‐a (an indicator of algae), with limits placed on TN and TP to help achieve the
chlorophyll‐a goal.
Table II‐2 demonstrates the fact that eutrophying pollution, as indicated by chlorophyll‐a, is
caused by several parameters, not just TN. This table summarizes some of the results of multiple linear
regression analyses conducted by the EPA. It indicates that TN or TP alone are poor predictors of
eutrophication.
5
Thus attempts to predict chlorophyll‐a concentrations with TN or TP alone yielded low R2
values (did not account for a large amount of the variability in the data), and high AIC values (poor
model parsimony). On the other hand, chlorophyll‐a concentrations were predicted much better when
TN and TP were considered together, along with other variables, such as the alkalinity and color of the
surface water.
Table II‐2. Relationship Between Chlorophyll‐a and Various Parameters Model Description Adj. R2 AIC
1 Chl‐a == f(TN) 0.527 1370 2 Chl‐a = f(TP) 0.358 1514 3 Chl‐a = f(TN + nutrient region) 0.562 1350 4 Chl‐a = f(TP + nutrient region) 0.396 1493 7 Chl‐a = f(TN + alk + color + color2 + pH) 0.697 1185 10 Chl‐a = f(TN + TP + alk + color + color2) 0.756 1057
AIC = Akaike’s Information Criterion, which penalizes models according to the number of explanatory variables (US EPA, 2010a, pg 81). Note: all variables in the models were significant; N = 474 (most complete data set with all variables); variables enclosed within the f( ) are each represented in the model as the variable value multiplied by a constant regression coefficient. “alk” = alkalinity. Adapted from US EPA (2010a).
Consistent with this finding was the fact that the DEP found a poor correlation between TN and
DO concentrations in the Gordon River Extension TMDL (R2 = 0.44; FDEP 2008b, p. 10). The DEP also
found very poor to fair correlations between TN and both DO and chlorophyll‐a in its analysis for the
Caloosahatchee Estuary TMDL (FDEP, 2009).
The National Academy of Sciences charged its National Research Council (NRC) with the task of
writing a report that would advise government agencies regarding nutrient pollution of coastal rivers
and bays. A technical summary of this report was published in a peer‐reviewed journal (Howarth et al.,
2002). The NRC seemed to give equal weight to N and P as sources of the problem. The authors also
stated that animal waste (livestock, urban animals, etc.) and atmospheric deposition are significant
sources of N, and a significant mechanism for P loss to surface water is via eroded sediments. Thus any
fertilizer ordinance that indirectly leads to reduce vegetation density – which can lead to increased
erosion ‐‐ may adversely impact water quality.
Nutrient impacts on the Everglades has also been studied. An investigation by Gaiser et al.
(2005) indicated that TP is a parameter of concern for the Everglades.
6
Elser et al. (2007) conducted a global metastudy of over 1000 freshwater, marine, and terrestrial
experiments. They found that simultaneous N and P enrichment produces “. . . strongly positive
synergistic responses in all three environments.”
Finally, one key environmental parameter that is missing in these discussions is temperature. An
increase in temperature causes a decrease in DO, other factors being equal. Decreases in shading (tree
removal) and increases in impervious land cover cause the warming of surface water.
Thus it appears that it will be difficult to achieve desired DO/chlorophyll‐a goals by only
restricting the environmental loading of one parameter (TN). TN is explicitly the focus of one action,
the Gordon River Extension TMDL, and implicitly and explicitly the focus of the proposed Collier County
ordinance.
7
III. RELATIVE SOURCE CONTRIBUTION
Section II above illustrates the concept that water resource protection requires a comprehensive
evaluation of multiple water quality parameters. This section explains the concept that multiple sources
of these parameters should be considered, and that the socioeconomic burdens placed on the different
sources should be roughly proportional to the potential impacts they are causing.
Any regulatory or management strategy to protect water resources should be based on an
understanding of the causative factors of the problem. For example, in computer simulation modeling of
ground water and surface water impacts, experienced scientists conduct sensitivity analyses of the key
parameters that ‘drive’ the result. Once the scientist has identified these sensitive parameters, the
greatest effort can be put into reducing the uncertainties in the most important parameters.
This should be an analogy for ordinances, legislation, and regulation that target water quality
protection in the context of eutrophication and blooms of harmful algae. In other words, regulators and
legislators should consider which restrictions will yield the most ‘bangs for the buck’, at societal costs
that will not be prohibitive. This concept is illustrated in Figure III‐1.
Figure III‐1. Conceptual Analysis of Costs and Benefits
8
In scenario 1, a certain activity or group is causing much of the environmental impacts, so it
endures much of the costs to mitigate those impacts, as is appropriate. In scenarios 2 and 3, the activity
or group causes a relatively small part of the problem, and the costs incurred are either disproportional
or proportional, respectively. We suggest that sufficient study has not yet been done with regard to the
proposed Collier County ordinance, but turf fertilization is likely described by scenarios 2 or 3. The
remainder of this section and section IV provide some scientific support for this public debate.
Specifically, section A below lists potential sources of key pollutants that can cause eutrophication and
harmful algal blooms. Section B provides relevant examples of relative source contributions. Section IV
summarizes the results of selected key monitoring, runoff, and leaching studies, as well as a summary of
key concepts relevant to turf hydrology.
A. Possible N, P, and Sediment Sources
The target of the Gordon River Extension TMDL and the proposed Collier County fertilizer
ordinance is N. The Lake Trafford TMDL and the EPA nutrient criteria target P as well as N as causes of
low DO. In addition, sediments, characterized as “total suspended solids” (TSS) in water samples, are
significant sources of P (Zhang et al., 2002; Howarth et al., 2002). Therefore this discussion will address
sources of TSS and TP, as well as TN.
TN, TP, and TSS can originate from point sources and nonpoint sources, in accordance with the
way the terms are traditionally used under the Clean Water Act. Typical point sources of these
parameters are wastewater treatment plants and municipal separate storm sewer system permittees
(towns, cities, and counties). All three parameters are discharged by these point sources.
Table III‐1. Nonpoint Sources of TN, TP, and TSS Parameter Potential Significant Sources TN Synthetic fertilizers used in turf and crop management, manure, urban animal waste
(pets, birds, etc.), decaying plant matter (e.g., fallen leaves and grass clippings), septic tanks, animal feedlots, atmospheric deposition (wet and dry)*.
TP All of the above, except atmospheric deposition, plus eroded sediments. TSS Bare ground, urban particulates, row‐crop/conventional tillage agriculture, poorly
maintained turf, woodlands, animal feedlots, construction sites. * Atmospheric deposition can often be a significant source of TN, e.g., 1% ‐ 40% of the TN deposited directly onto estuaries and coastal waters (Howarth et al., 2002), and 25% ‐ 28% of the TN loaded into the Chesapeake Bay watershed (US EPA, 2010b). The ultimate TN atmospheric sources are motorized vehicles, power plants, etc. It is likely that the atmosphere is not as large of a TN source in Collier County as these other locations, i.e., perhaps (?) less than 10%.
9
B. Relative Source Contributions
Turf fertilization is almost certainly a source of TN loading to surface water and ground water, to
at least a limited extent. For example, shallow ground water immediately adjacent to residential lawns
north and west of Orlando had an average nitrate‐N concentration of 2.4 mg/L, which was above the
concentration in two background wells (MACTEC, 2009), and somewhat higher than might be expected.
[NOTE: Apparently, the study was not designed to measure the extent to which the nitrate
concentrations dissipate prior to discharge to a sensitive water body. (This study is discussed again in
IV(B) below.)]
However, there is significant doubt that turf fertilizer has caused a majority of the TN load to
water resources in Collier County. Further, fertilizer restrictions as proposed may cause an increase in TP
and TSS runoff to surface water, which could counteract any gain by TN reductions.
The basis for the doubt about the degree to which fertilizer applied to turf is a major cause of
nutrient pollution problems is explained four ways. First, we have already presented above the concepts
that this phenomenom has multiple contributory sources. Second, immediately below, in subsections 1‐
4, is a general discussion of relative source contributions. Third, section IV summarizes some key
scientific concepts regarding turfgrass hydrology and TN, TP, and TSS loss from turf. Finally, part of
section IV also summarizes the results of a comprehensive, golf course water quality monitoring study.
1. Example from the Wekiva River Basin
Figure III‐2 was recently created by the DEP based on a study by MACTEC (2009) of the
Wekiva River Basin, which is north and west of Orlando. It depicts the results of an analysis that
residential and golf fertilizer applications only constitute 15% and 2%, respectively, of the
estimated nitrate leading to that basin. [NOTE: “OSTDS” in the figure refers to septic systems.]
10
Figure III‐2. Nitrate Loading in the Wekiva River Basin
2. Examples from the Lake Trafford TMDL
Figures III‐3a and b are adapted from the Lake Trafford TMDL report (FDEP, 2008a).
They indicate that 41% of the TN and 17% of the TP originate in the combination of three
residential land uses. Turf fertilization would be some subset of these residential land use
numbers. Other urban/suburban sources are mammal and bird waste, leaky sewer systems,
natural vegetation sources, and combustion engine exhaust.
Figure III‐3a. Annual Average TP Loads (lbs/yr) from Different Land Use Types to Lake Trafford Over a 10‐Year Period
11
Figure III‐3b. Annual Average TN Loads from Different Land Use Types to Lake Trafford over a 10‐yr
Period
3. Chesapeake Bay Example
Figure III‐4 was based on the Chesapeake Bay TMDL (US EPA, 2010b). This is the largest,
most comprehensive, most well‐studied TMDL to date. This indicates the urban/suburban land
use is responsible for 8% of the TN load to the Bay watershed. [NOTE: Turf is the #1 “crop” in
the six‐state watershed.)
8% N
92% N
EPA‐Modeled Land Use Contributions to the Bay(Bay Watershed Model 2009 scenario)
Urban/Suburban Land UseOther Sources
Figure III‐4. EPA‐Modeled Land Use Contributions to the Chesapeake Bay (Adapted from US EPA (2010b))
12
4. Summary
The data underlying Figures III‐2, III‐3a, III‐3b, and III‐4 were created using computer
simulation modeling. The following limitations should be kept in mind. 1) Conservative
assumptions about turf management are often built into assessments such as these, when turf
is even explicitly modeled. 2) Some specific assumptions and input parameters are often not
clearly explained. 3) Only Figure III‐2 specifically attempts to address turf fertilization. This
activity is otherwise a subset of other land use classifications in the other depictions of modeling
results. 4) Actual monitoring studies have rarely demonstrated that turf fertilization has had
significant impacts on the aquatic ecosystem. This observation is discussed further in section IV
below.
Thus these figures, combined with the discussion above in this section, as well as in
section IV below, indicate that turf is almost certainly not a dominant contributor to
eutrophication and harmful algal blooms. It is likely one of several contributors to the problem
‐ ‐ particularly the fertilizer that is inappropriately applied to paved surfaces ‐ ‐ but the
comprehensive analysis to determine the relative contributions of this source in the Collier
County area has not yet been done. A discussion of the underlying science follows, in section IV.
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IV. TP AND TN LOSS FROM TURF VIA RUNOFF AND LEACHATE
Sections A and B below briefly summarize the results of several monitoring studies. These
studies tend to be watershed scale. The scale relevant to the discussions in sections C and D tend to be
at the field level (subbasin or test plot). Section C offers some key concepts on hydrology, and section D
focuses on individual parameters relevant to fertilizer legislation and regulation.
A. The Results of Two Comprehensive Metastudies and One Local Study
We have been involved in several evaluations of water quality impacts by golf courses. In
addition to studies of individual golf courses, we have published the following keystone papers in the
peer‐reviewed literature: Baris et al. (2010); Cohen et al. (1999); and Cohen et al. (1990).
Baris et al. (2010) was a metastudy of ground water and surface water monitoring results from
80 North American golf courses, including 14 in Florida. Over 38,000 data points were evaluated. The
authors concluded that pesticide impacts on ground water and surface water, and N and P impacts on
ground water, were de minimus. (The average concentration of nitrate in ground water was 1.1 ± 1.9
mg/L [n = 1,683].) The results did indicate a pattern of exceedances for nutrients in surface water, but
these were mostly edge‐of‐field storm event runoff results compared with the EPA’s Level III ecoregional
criteria, which were developed for baseline conditions. There is a strong ground water/surface water
linkage in Collier County ‐ ‐ ground water can provide the baseflow for much of the surface water.
Further, there is not a high degree of topographic relief nor impermeable soils (hydrologic soil group D)
in the areas most likely to have the most managed turf (cities and towns). Therefore it is appropriate to
place a significant focus on ground water loading.
Cohen et al. (1999) was a predecessor study to Baris et al. (2010), and reached similar
conclusions, although P was not evaluated. Finally, Cohen et al. (1990) was an EPA‐sponsored ground
water monitoring study of four golf courses in a highly vulnerable environment on Cape Cod. Monitoring
wells were installed and sampled over a 1½ year period. Minimal ground water impacts were found.
14
B. Wekiva River Basin Study
This study is briefly mentioned in section III(B) above, and its results are depicted in Figure III‐2.
One component of the study was the installation of 26 monitoring wells in the midst of a residential area
north and west of Orlando (MACTEC, 2009). Sampling occurred over a period of nine months. The
average nitrate‐N concentration was 2.4 mg/L, compared with an average of 0.3 mg/L in two
background wells. The difference is statistically significant. No conclusions were reached about
ecological significance, although Figure III‐2 above indicates agricultural fertilizers and septic systems
combined contribute far more nitrate to the system ‐ ‐ 52% of the total ‐ ‐ than do residential and golf
fertilizers combined ‐ ‐ 17%. We are not aware of any other studies such as this in Florida.
C. Turfgrass Hydrology
More rainfall is required to generate runoff from turf than most other land uses. (Notable
exceptions are dense woodland and meadows.) In other words, only a small subset of storms is actually
sufficient in intensity to produce significant runoff from well managed turf. This point is illustrated with
the calculations presented in Appendix A. We used the USDA’s runoff curve number (CN) approach (TR‐
55) to determine that only an extremely small number of storms would be sufficient to generate
moderately significant runoff (a depth of one quarter inch). The specific numbers calculated by this
method are 1‐2 per year depending on the turf/soil combination, and for an average antecedent
moisture condition. However, the actual number of storms would be greater due to the fact that the CN
approach is based on 24 hr storm events, and shorter duration storms with equal volumes of rain will
increase the number of runoff‐generating events. Mitigating this is the fact evapotranspiration (ET)
rates are so high during the all‐important, rainy summer months that there is only a modest surplus of
rain relative to ET, a net of 1.19 inches for June‐August (Toro Rainfall‐Evapotraspiration Data, 1966; for
Ft. Myers).
Semiquantitative support for this thesis can be found in Tables 6‐6, 6‐7, and 6‐10 of Harper and
Baker (2007), who calculated very low runoff depths and coefficients for well drained to moderately well
drained conditions for this area of Florida.
15
Why is turf such a good filter with such a good retention capacity? It has a very dense cover,
root system, and thatch layer. Thatch is “An intermingled organic layer of dead and living shoots, stems,
and roots that develops between the zone of green vegetation and the soil surface” (Beard, 2002). It is
important for environmental assessments because it retards water and contaminant movement
relative to virtually any other land cover.
D. Edge‐of‐Field Runoff and Leaching Studies
There is a very large body of literature on pesticide and nutrient losses from turf. Fewer studies
have been done on TSS losses from turf, although turf has been used by civil engineers and farmers for
several decades as a BMP to prevent impacts from eroded sediments on surface waters and wetlands. It
is beyond the scope of this report to summarize this general subject in any detail whatsoever. The
reader is referred to two key recent books on the subject, Nett et al. (2008) and Beard and Kenna
(2008). More recently, UF/IFAS professors have specifically addressed the science relevant to this type
of fertilizer ordinance in Hochmuth et al. (2011); and the UF/IFAS comment letter to M. Hatcher from T.
Nell (March 9, 2011). These are very good summaries of the relevant science at the field scale and test
plot scale. [NOTE: We have read these IFAS documents, but we have not consulted with the authors
while working on this report.]
The central theme of the peer‐reviewed literature is the following: properly maintained turf
releases minimal amounts of nitrate and phosphate into the leachate and runoff; it is also retains
sediments fairly tightly compared with most, if not all, other land uses except for pavement. However,
the literature – coupled with our experience – also indicates that most established stands of turf need
minimal additions of P, P should only be applied in response to a soil test, and P is frequently applied
when it is not needed.
The readers of this report should consult the two books and the two IFAS documents cited
above. Following is just a brief sample of additional key literature in this field.
16
1. Runoff
Kussow (2008) demonstrated an increase in N runoff when the turfgrass was under
fertilized. Petrovic and Easton (2005), and Bierman et al. (2010) have found analogous results
with P. Zhang et al. (2002) found that Florida soils have much leachable P, which could be
available if the soils are allowed to erode as a result of highly restricted fertilization applications.
Runoff from well managed turf with minimal slope, on well‐ to moderately‐well drained soils is
an infrequent event (see section C above and Appendix A).
2. Leaching
The literature is fairly consistent: leachate of significant concentrations of nitrate
typically only occurs when rates exceeding 1 lb N/1000 ft2 are applied in a water soluble form.
In our experience and knowledge, nitrate leaching rates at the field scale and in test plots seem
to be in the 0.1‐8% range. See, for example, Petrovic (1990), Trenholm et al. (2011), Erickson et
al. (2001), and Raciti et al. (2008). See also the work we published previously on golf course
water quality monitoring (Baris et al., 2010; Cohen et al., 1999) and briefly summarize in section
A above.
17
V. CONCLUSIONS AND RECOMMENDATIONS
Various State, county, and local ordinances have legislated Best Management Practices (BMPs)
for turf fertilization. The science indicates a holistic and equitable approach should be taken toward
such regulation, but that does not appear to have occurred in the development of certain aspects of the
current Collier County proposal.
Section A below comments on several of the provisions in the recently proposed Collier County
fertilizer ordinance. Section B provides some BMP recommendations that should be considered for the
next draft of the ordinance.
A. The Collier County Proposed Ordinance
The draft ordinance should be revised for general and specific reasons. The general reasons are
as follows. 1) The ordinance should not be based on a desire to limit TN as a key driver to design and
implement a measure that will protect Collier County’s water resources. Rather, it should more
comprehensively use the available science and incorporate considerations for TP, TSS, and temperature,
as appropriate, as factors whose management can be used to increase DO and decrease chlorophyll‐a.
2) It should become part of a broader strategy to consider a wide variety of activities and land uses, and
adverse impacts of this ordinance should be considered in that context. If this is not done, it is possible
that socioeconomic impacts to one sector will occur with minimal benefits to the environment.
More specific comments follow:
• Timing of fertilizer applications – the provision for the summer ban should be abolished.
• Fertilizer‐free zones – this should not be applied to professionally managed turf, as long as
certain safeguards are maintained.
• Fertilizer content – the 50% slow release percentage is unnecessarily high if consumer
packaging is marketed that is more conducive to apply reduced rates, e.g., 0.7 lb N/1000 ft2,
and it may be a problem for products in commerce.
• Fertilizer application rates – the limit for home lawns should be raised to 5 lb/1000 ft2.
• Sections 9 and 10, “Application Practices” and “Management of Grass Clippings…” are well
written, important, and should be immediately implemented.
18
B. Recommended BMPs
1. Golf Courses
• Complete the BMP checklist in Appendix B every year.
• Sample and analyze the soil annually for P and N requirements in accordance with the
procedures described on p. 51 of the Florida golf course BMP guidance (FDEP, 2007).
Apply no more P or N than is recommended by the soil testing lab.
• Sample and analyze the plant tissue (clippings) annually for P and N requirements in
accordance with the procedures described on p. 52 of the Florida golf course BMP
guidance (FDEP, 2007). Apply no more P or N than is recommended by the tissue testing
lab.
• Never apply more than 0.5 lb N/1000 ft2 in a water‐soluble, quick‐release form at one
time to mature turf, nor at intervals spaced more closely than 14 days with the
exception of renovations. A 7‐day interval is acceptable for a renovation.
• Only use drop spreaders, or rotary spreaders with deflector shields, when applying
granular fertilizers within 10 ft of surface water.
• Do not allow drift of spray droplets into surface water for conventional fertilization. For
fertigation, adjust the irrigation heads so the spray is not directed to impact sensitive
surface water resources.
2. Professional Lawn Care Companies
• We understand that professional lawn care operators undergo a comprehensive
certification program. We are not familiar with this program, but a suggestion is that
consideration be given to develop a checklist for this industry similar to the checklist
developed for the golf industry (see B(2) above and Appendix B). It is possible that such
a checklist may be superfluous, or it may be useful.
• Apply fertilizer N at rates consistent with the South Florida recommendations in Tables 5
and 6 of the Florida turf and ornamental BMP guidance document (FDEP, 2008), with
the following exception: the total amount of N applied in one year should not exceed 5
lb/1000 ft2.
19
• Follow the 16 BMPs listed on p. 39 of FDEP (2008).
• Similar to the first recommendation, implementation of the following may not be
necessary within the context of the existing certification program: conduct soil and
tissue testing annually, in accordance with the guidance on pp. 36‐38 of FDEP (2008). Do
not exceed P and N application rates indicated by the lab analyses.
• Only use drop spreaders, or rotary spreaders with deflector shields, when applying
granular fertilizers within 10 ft of surface water.
• Do not allow drift of spray droplets into surface water.
3. Homeowners and County/Municipal Governments
• Implement a strong program to educate the public to keep fallen leaves and grass
clippings out of the street and off impervious surfaces around the home.
• Implement a strong program to educate the public about the importance of preventing
fertilizer applications to impervious surfaces, and the need for immediate removal if it
does happen.
20
REFERENCES
Baris, R.D., S.Z. Cohen, N.L. Barnes, J. Lam, and Q. Ma. 2010. Quantitative Analysis of Over 20 Years of Golf Course Monitoring Studies. Environ. Tox. and Chem. 29(6):1224‐1236.
Beard, J.B. and M.P. Kenna (Eds). 2008. Water Quality and Quantity Issues for Turfgrasses in Urban Landscapes. The Council for Agricultural Science and Technology (CAST), Ames, IA, 298 pp.
Beard, J.B. 2002. Turf Management for Golf Courses. Second Edition. Ann Arbor Press, Chelsea, MI, p. 766.
Bierman, P.M., B.P. Horgan, C.J. Rosen, and A.B. Hollman. 2010. Phosphorus Runoff from Turfgrass as Affected by Phosphorus Fertilization and Clipping Management. J. Environ. Qual. 39:282‐292.
Chopra, M., M. Wanielista, S. Kakuturu, M. Hardin, and E. Stuart. 2011. Evaluation of Pollution Levels Due to the Use of Consumer Fertilizers under Florida Conditions. Final Report for the Florida Department of Transportation by Stormwater Management Academy, Orlando, FL. 201 pp.
Cohen, S.Z., A.J. Svrjcek, T. Durborow, N.L. Barnes. 1999. “Water Quality Impacts by Golf Courses,” J. Environ. Qual., 28(3):798‐809.
Cohen, S.Z., S. Nickerson, R. Maxey, A. Dupuy, and J.A. Senita. 1990. "A Ground Water Monitoring Study for Pesticides and Nitrates Associated with Golf Courses on Cape Cod," Ground Water Mon. Rev., 10(1), 160‐173.
Dodds, W.K., J.M. Blair, G.M. Henebry, J.K. Koelliker, R. Ramundo, and C.M. Tate. 1996. Nitrogen Transport from Tallgrass Prairie Watersheds. J. Environ. Qual. 25:973‐981.
Elser, J.J., T. Andersen, J.S. Baron, A‐K. Bergström, M. Jansson, M. Kyle, K.R. Nydick, L. Steger, and D.O. Hessen. 2009. Shifts in Lake N:P Stoichiometry and Nutrient Limitation Driven by Atmospheric Nitrogen Deposition. Science 326:835‐837.
Elser, J.J., M.E.S. Bracken, E.E. Cleland, D.S. Gruner, W.S. Harpole, H. Hillebrand, J.T. Ngai, E.W. Seabloom, J.B. Shurin, and J.E. Smith. 2007. Global Analysis of Nitrogen and Phosphorus Limitation of Primary Producers in Freshwater, Marine and Terrestrial Ecosystems. Ecology Letters 10:1135‐1142.
Erickson, J.E., J.L. Cisar, G.H. Snyder, D.M. Park, and K.E. Williams. 2008. Does a Mixed‐Species Landscape Reduce Inorganic‐Nitrogen Leaching Compared to a Conventional St. Augustinegrass Lawn? Crop Science 50:1030‐1036.
FDEP, 2008a. Kang, W‐J. and D. Gilbert. June 2008. TMDL Report Nutrient, Un‐ionized Ammonia, and DO TMDLs for Lake Trafford (WBID 3259W). Florida Department of Environmental Protection, Tallahassee, FL.
FDEP. 2008b. Baily, N. August 19, 2008. TMDL Report Dissolved Oxygen TMDL for the Gordon River Extension, WBID 3278K (formerly 3259C). Florida Department of Environmental Protection, Tallahassee, FL.
FDEP 2009. Bailey, N., W. Magley, J. Mandrup‐Poulsen, K. O’Donnell, and R. Peets. 2009. Final TMDL Report: Nutrient TMDL for the Caloosahatchee Estuary. Florida Department of Environmental Protection, Tallahassee, FL.
Gaiser, E.E., J.C. Trexler, J.H. Richards, D.L. Childers, D. Lee, A.L. Edwards, L.J. Scinto, K. Jayachandran, G.B. Noe, and R.D. Jones. 2005. Cascading Ecological Effects of Low‐Level Phosphorus Enrichment in the Florida Everglades. J. Environ. Qual. 34:717‐723.
Greening, H. and A. Janicki. 2006. Toward Reversal of Eutrophic Conditions in a Subtropical Estuary: Water Quality and Seagrass Response to Nitrogen Loading Reductions in Tampa Bay, Florida, USA. Environ. Mgmt 38(2):163‐178.
Harper, H. and D. Baker. 2007. Evaluation of Current Stormwater Design Criteria in Florida. Prepared by Environmental Research and Design for the Florida Department of Environmental Protection. Available: http://www.dep.state.fl.us/water/nonpoint/docs/nonpoint/SW_TreatmentReportFinal_71907.Pdf
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Hochmuth, G., T. Nell, J. Sartain, J.B. Unruh, C. Martinez, L. Trenholm, and J. Cisar. 2011. Urban Water Quality and Fertilizer Ordinances: Avoiding Unintended Consequences: A Review of the Scientific Literature. Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL, 31 pp.
Howarth, R.W., A. Sharpley, and D. Walker. 2002. Sources of Nutrient Pollution to Coastal Waters in the United States: Implications for Achieving Coastal Water Quality Goals. Estuaries 25:656‐676.
IFAS (Institute of Food and Agricultural Sciences). March 9, 2011. Letter from T. Nell (U.FL/IFAS) to M. Hatcher (Collier Co. FL, Dept of Land Dev. Svcs), re: Scientific assessment of the Collier County Florida‐Friendly Use of Fertilizer on Urban Landscapes. University of Florida, IFAS, 10 pp.
Kaufman, G., J.L. Oliver, D.A. Thomas, T. Wool, L.L. Yuan, J. Butcher, J. Gerritsen, M.J. Paul, and L. Zheng. 2010. Technical Support Document for U.S. EPA’s Final Rule for Numeric Criteria for Nitrogen/Phosphorus Pollution in Florida’s Inland Surface Fresh Waters. http://water.epa.gov/lawsregs/rulesregs/upload/floridatsd1.pdf
Kussow, W. R. 2008. Management Practices Affecting Nitrogen and Soluble Phosphorus Losses from an Upper Midwest Lawn. Chapter 1, pages 1–18. In: M.T. Nett, M. J. Carroll, B.P. Horgan, A.M. Petrovic (eds.), Fate of Nutrients and Pesticides in the Urban Environment. American Chemical Society.
MACTEC. October 2009. Final Data Summary Report Sources of Nitrate in the Wekiva River Basin Phase II. MACTEC, Newberry. FL. 53 pp. [Subsequent to this report, the DEP extracted date to produce the relative source contribution of nitrate depicted in figure III‐2: http://www.dep.state.fl.us/water/wekiva/index.htm]
NACWA. March, 2011. Nutrient Summit Outcomes and Issue Paper. National Association of Clean Water Agencies, Washington, DC. Available at: http://op.bna.com/env.nsf/r?Open=fwhe‐8f9sq2.
Nett, M.T., M.J. Carroll, B.P. Horgan and A.M. Petrovic. The Fate of Nutrients and Pesticides in the Urban Environment. ACS Symposium Series 997. American Chemical Society, Washington, DC, 277 pp.
Petrovic, A.M. 1990. The Fate of Nitrogenous Fertilizers Applied to Turfgrass. J. Environ. Qual., 19:1‐14. Petrovic, A.M., and Z.M. Easton. 2005. The Role of Turfgrass Management in the Water Quality of Urban
Environments. Int’l. Turfgrass Soc. Res. J. 10:55‐69. Raciti, S.M., P.M. Groffman, and T.J. Fahey. 2008. Nitrogen Retention in Urban Lawns and Forests. Ecol.
Appl. 18:1615‐1626. Trenholm, L.T., J.B. Unruh, J.B. Sartain. 2011 (in press). Nitrate Leaching and Turf Quality in Established
‘Flaoratam’ St. Augustinegrass and ‘Empire’ Zoysiagrass. Crop Science. USDA. 1986. Urban Hydrology for Small Watersheds. TR‐55 (Technical Release 55). United States
Department of Agriculture, Natural Resources Conservation Service, Conservation Engineering Division, Washington DC.
US EPA 2010a. Kaufman, G., J.L. Oliver, D.A. Thomas, T. Wool, L.L. Yuan, J. Butcher, J. Gerritsen, M.J. Paul, and L. Zheng. 2010. Technical Support Document for U.S. EPA’s Final Rule for Numeric Criteria for Nitrogen/Phosphorus Pollution in Florida’s Inland Surface Fresh Waters. U.S. Environmental Protection Agency, Washington, DC. http://water.epa.gov/lawsregs/rulesregs/upload/floridatsd1.pdf
US EPA 2010b. December 29, 2010. Chesapeake Bay Total Maximum Daily Load for Nitrogen, Phosphorus and Sediment. U.S. Environmental Protection Agency Region 3, Philadelphia, PA and Annapolis, MD; U.S. Environmental Protection Agency Region 2, New York, NY; and U.S. EPA, Washington, DC. Available at: http://www.epa.gov/reg3wapd/tmdl/ChesapeakeBay/tmdlexec.html.
Zhang, M.K., Z.L. He, D.V. Calvert, P.J. Stoffella, Y.C. Li, and E.M. Lamb. 2002. Release Potential of Phosphorus in Florida Sandy Soils in Relation to Phosphorus Fractions and Adsorption Capacity. J. Environ. Sci. Health A, 37(5):793‐809.
A‐1
APPENDIX A. TR‐55 Runoff Calculations and Rainfall Threshold Determinations for Collier County Turf
A‐2
TR‐55 Runoff Calculations and Rainfall Threshold Determination for Collier County Turf
The USDA’s (1986) TR‐55 was used to estimate the amount of rainfall needed to produce ¼” of
runoff. Two curve numbers (CN) were used in the calculations: 50 (between hydrologic soil group A and
B, >75% grass cover (i.e., managed turf) and 61 (hydrologic soil group B, >75% grass cover); Table 2‐2a).
The rainfall amount necessary to produce ¼” of runoff is 3.7” for CN=50 and 2.7” for CN=61. The SCS
runoff equation presented in the TR‐55 manual was used to confirm the runoff amount:
Q = (P ‐ 0.2S)2/(P + 0.8S),
where
Q = runoff (in), P = rainfall (in), and S = potential maximum retention after runoff begins (in). S is
related to the cover and soil conditions by the CN: S=1000/CN‐10.
Thus, S=6.39 for CN=61 and the runoff amount = 0.25” is provided in the calculation: Q = (2.7 ‐
0.2(6.39)2/(2.7 + 0.8(6.39)) = 0.25”. Therefore, 2.7” of rain is needed to produce ¼” of runoff for land
with CN=61. Similarly, S=10 for a CN of 50, and the rainfall amount needed to produce ¼” of runoff is
3.7”: Q = (3.7 ‐ 0.2(10))2/(3.7 + 0.8(10)) = 0.25”.
The results above (i.e., rainfall of 2.7” and 3.7”) were used to determine the percentage of
annual rain events that will produce ¼” of runoff in the Ft. Myers area (the closest rainfall station to
Collier County (Zone 4) in Harper and Baker, 2007, Figure 4‐3). Table 3‐2 (Harper and Baker, 2007) shows
that only 1.8% of rain events are greater than 2.7” and only 0.8% of rain events are greater than 3.7”.
These percentages translate to 1.975 and 0.925 events per year, respectively (Fort Myers Station 3186;
personal communication D. Baker, 3/25/2011).
SEE SECTION IV(C) FOR CONTEXT AND LIMITATIONS.
B‐1
APPENDIX B. Golf Course Best Management Practice Checklist (from Appendix E of FDEP (2007))
B‐2
B‐3
B‐4
B‐5
B‐6
B‐7
B‐8
B‐9