United States
Environmental Protection
Agency
Environmental Monitoring
Systems Laboratory
Las Vegas, NV 89193-3478
Research and Development
EPA/620/SR-94/014  June 1994
 Project  Summary
Environmental Monitoring  and
Assessment Program:
Agroecosystem  Pilot Field
Program Report-  1992
C. Lee Campbell, Jeff M. Bay, Anne S. Hellkamp, George R. Hess, Michael J.
Munster, Karen E. Nauman, Deborah A. Neher, Gail L. Olsen, Steven L. Peck,
Brian A. Schumacher, Kurex Sidik, Mark B. Tooley, and David W. Turner
  The Agroecosystem Resource Group
(ARG) of the Environmental Monitoring
and Assessment Program (EMAP) has
developed a five-year strategy for the
development, evaluation, and imple-
mentation of a suite of indicators for
monitoring the status and trends of
agroecosystem condition on a regional
and national basis. The five-year pe-
riod includes time to test concepts re-
lating to design, indicators, quality as-
surance, logistics, information manage-
ment, data analysis, assessment, and
reporting at the pilot and demonstra-
tion  program stages.  A primary em-
phasis is on the development of close
working relations  between personnel
from the U.S. Environmental Protection
Agency (EPA), the U.S. Department of
Agriculture's (USDA) Agricultural Re-
search Service (ARS) and National Ag-
ricultural Statistics Service (NASS) and
the ARG. The 1992 Pilot Field Program
in North Carolina evaluated all aspects
of the  monitoring program  for a se-
lected suite of indicators. The Pilot was
conducted over an area large enough
to provide reliable answers to ques-
tions concerning the operation of the
monitoring program but small enough
to be physically and fiscally manage-
able. Results will be used to plan for a
regional demonstration project and to
address specific concerns of applying
the program indicators in a different
geographic area of the country. In ad-
dition, results  will  assist the ARG in
establishing an acceptable  sampling
design, set of core indicators,  logis-
tics, quality assurance and information
management protocols, and an assess-
ment framework for use in monitoring
the status, trends, and condition of the
nation's agroecological resources.
  This Project Summary was developed
by EPA's Environmental Monitoring
Systems Laboratory, Las Vegas, NV, to
announce key findings of the research
project that is fully documented in a
separate report of the same title (see
ordering information at back).
                    •ti
Introduction
  In 1992 a Pilot Field Program was con-
ducted in  North Carolina by members of
the Environmental Monitoring and Assess-
ment Program's (EMAP) Agroecosystem
Resource Group (ARG). EMAP originated
within the  Office of Research and Devel-
opment (ORD) of the U.S. Environmental
Protection Agency (EPA) and  is now an
interagency,  interdisciplinary  initiative to
monitor the condition of the nation's eco-
logical resources. The U.S. Department of
Agriculture's (USDA) Agricultural Research
Service (ARS) provides technical leader-
ship for the Agroecosystem component,
one of  eight resource categories within
EMAP.  The  ARG cooperated with the
USDA's  National  Agricultural Statistics
Service (NASS) in the development and
data collection aspects of the 1992 Pilot.
The three principal agencies cooperated
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 in the Pilot as the first developmental step
 toward  the  implementation of a plan  for
 monitoring  the ecological  condition  of
 agroocosystems in the United States.
   The mission of the ARG is to develop and
 implement a program that will, in the long
 term, monitor and  assess the condition and
 extent of the nation's agroecosystems from
 an ecological perspective through an inter-
 agency process. The specific objectives of
 the ARG parallel the overall EMAP objec-
 tives. When fully implemented the pro-
 gram will
   •  Estimate the  status, trends, and
     changes in selected  indicators of the
     condition of the nation's agroecological
     resources  on a regional basis with
     known confidence.
   •  Estimate the geographic coverage and
     extent of the nation's agroecological
     resources with known confidence.
   •  Seek associations between selected
     Indicators of natural and anthropo-
     genic stresses and indicators of the
     condition of agroecological resources.
   •  Provide annual statistical summaries
     and periodic  assessment  of the
     nation's agroecological resources.
   An agroecosystem is a dynamic asso-
 ciation of crops, pasture, livestock,  other
 plants and animals, atmosphere, soils, and
 water. The  agroecosystem includes not
 only the field or pasture but also the asso-
 ciated border areas such as windbreaks,
 fence rows, drtchbanks, and farm ponds.
 The agroecosystem boundary depends on,
 and varies with, the process being consid-
 ered. Agroecosystems interact with larger
 landscapes,  which include  uncultivated
 land, drainage networks,  human commu-
 nities, and  wildlife. The landscape is the
 area that directly affects the ecology of
 the agroecosystems and is directly affected
 by agroecosystem processes. The  land-
 scape boundary  also  depends on, and
 varies with, the process being considered.
  The sustainability of agroecosystems is
 of primary importance to the people of the
 United States and the world.  Although
there are several aspects  of sustainability,
the ARG is interested in the ecological
 sustainability of agroecosystems. An
 agroecosystem  is  ecologically sustainable
 ii it maintains or enhances its own  long-
term productivity  and biodiversity, the
 biodiversity  of  surrounding ecosystems,
 and  the quality of  air, water, and soil.
  The EMAP-Agroecosystems monitoring
 effort is based upon  assessment ques-
 tions related to three societal values. The
three societal values for agroecosystems
 are  the  components  of  ecological
 sustainability: quality of air, water,  and
 soil; productivity; and biodiversity.
   The ARG  developed a multiyear  pro-
 gram to establish the  regional  and na-
 tional implementation of a suite of indica-
 tors for  monitoring the  condition of
 agroecosystems.  The first stage of the
 program (1990) encompassed the initial
 evaluation  of (1) statistical  designs; (2)
 existing monitoring programs (i. e., NASS,
 Soil Conservation Service, and Economic
 Research Service); (3) assessment ques-
 tions and associated indicators (for their
 availability, validity, variability, and cost);
 (4) data management and analysis tech-
 niques; and (5) methods of reporting on
 indicators.  During 1990, a national moni-
 toring strategy was developed on the ba-
 sis of  these  evaluations.  In  the second
 stage of the program (1991) in-depth ex-
 aminations were conducted of several ar-
 eas critical to the planning and implemen-
 tation of the Pilot Field Programs: (1)  sta-
 tistical design options; (2) measurements
 associated with specific indicators and as-
 sessment questions; (3) sampling proto-
 cols; (4) cooperation with NASS; (5) logis-
 tics; (6) quality assurance; and (7) infor-
 mation  management. The 1992 Pilot in
 North Carolina, conducted in  cooperation
 with USDA NASS, tested aspects of the
 monitoring  program with a limited suite of
 indicators.  Results of the 1992 Pilot will
 be used to develop (based upon availabil-
 ity of funds) additional pilots  and regional
 demonstrations that eventually will lead to
 national implementation.

 Purpose and Objectives
  The  1992 Pilot was designed to evalu-
 ate aspects of the EMAP Agroecosystem
 monitoring  program critical to the imple-
 mentation of a  regional and national pro-
 gram. It was designed to address these
 program aspects  over  an   area  large
 enough to provide reliable  answers to
 questions concerning the operation of the
 monitoring  program but  small enough to
 be physically  and fiscally manageable.
  There were three  major objectives of
the 1992 Pilot:
  1. Compare  the relative efficiency, in
terms of cost and precision,  of two sam-
 pling frames.
  2. Evaluate an initial suite  of indicators
to
     •  Assess  the ability of  each indica-
       tor  to address  the  assessment
       questions of interest;
     •  Establish an initial range of values
       for  each indicator across the di-
       verse physiographic  regions  of
       North Carolina;
      •  Assess spatial variability of indi-
        cator values  within and  among
        sample units;
      •  Identify the usefulness and sensi-
        tivity  of each indicator in  deter-
        mining ecological condition; and
      •  Determine cost-effectiveness  for
        each indicator.
   3. Develop and refine plans for
      • Sampling
      • Logistics
      • Quality assurance
      • Data analysis,  summarization, and
        reporting
      • Information management
      • Ecological health indices and their
        interpretation
   The 1992 Pilot was also conducted to
establish a cooperative, working relation-
ship with NASS at  both the  state and
national level.  NASS has  a well estab-
lished nationwide network of enumerators
experienced  in conducting national sur-
veys. Also, growers throughout the United
States are familiar with  NASS personnel
and have confidence in NASS because of
the NASS data  confidentiality require-
ments.
   North Carolina was selected for the 1992
Pilot because
   1.  The physiographic diversity of the
      state  is  representative of the
      ecoregions of the southeastern re-
      gion of the United States.
   2.  NASS  is organized by state. Limit-
      ing the Pilot to one state simplified
      problem resolution.
   3.  Most of the ARG staff is located in
      Raleigh,  NC, which  facilitated lo-
      gistic activities.

Design and Statistical
Considerations
   The ARG considered two sampling plans
in the 1992 Pilot, each of which used the
NASS Area Frame segments as the basic
sampling units. The two plans differ in the
way the segments to be used for indicator
sampling  are selected.  The Pilot  study
evaluated the results of a sampling strat-
egy based on using the EMAP Hexagon
Design  to select the  NASS segment to
the Rotational Panel Plan that uses a sub-
set of segments from the NASS  June Enu-
rnerative Survey (JES). Fifty-one segments
distributed over 49 counties were used
from the EMAP Hexagon Design and 65
segments distributed  over 55 counties
were used from the Rotational Panel Plan.
Only fields planted with annually harvested

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herbaceous crops were eligible for selec-
tion as a sample unit. For each design,
crops in each field in each segment were
identified during the NASS JES. An aver-
age of three fields were selected at ran-
dom from  each of the 65  segments for
195 sample units for the Rotational Panel
Plan and from  each of the 51 segments
for 153 sample units for the Hexagon De-
sign. Ten  sample units from the Rota-
tional  Panel and 17  from  the Hexagon
Design were not sampled due to farmer
.refusal, inaccessibility  of the field, the field
not being in the designated resource class,
or enumerator error.
   Ponds and wells for sampling were iden-
tified from  lists developed by NASS from
the North Carolina JES. Initially, 51  ponds
and 81 wells were  identified from the Ro-
tational Panel  Design only. Because of
refusals and other factors identified previ-
ously,  40 ponds and 61 wells were actu-
ally sampled.
   Data were  assembled  from  three
sources: the JES, the EMAP Fall Survey
questionnaire,  and samples of soil and
water collected by NASS enumerators. All
questionnaire  data  were  compiled by
NASS and transmitted to the  ARG. Soil
samples were submitted to  one commer-
cial laboratory for analysis of physical and
chemical parameters and to another com-
mercial laboratory  for  nematode identifi-
cation and enumeration. All water samples
were analyzed by personnel  and contrac-
tors from EPA's Environmental Research
Laboratory in Athens, GA.
  The primary statistical tool used to sum-
marize indicator data from the 1992 Pilot
is the cumulative  distribution function
(CDF). Ninety percent confidence  bands
were added to each CDF in order to indi-
cate the precision of the estimated CDF.
The population reported  is  typically the
area of land in North  Carolina, the Pied-
mont region of North Carolina,  or  the
Coastal Plain region of North Carolina cul-
tivated with annually harvested herbaceous
crops.

Results
   Results are  presented for  the indicator
categories land use, crop productivity, soil
quality (physical and chemical), soil biotic
diversity, water quality, and agricultural
chemical use. In the full report, results for
each indicator are presented in a question
and answer format similar to what might
be used in  the future for annual statistical
summaries. In  a few  cases, boundaries
for acceptable  (nominal),  marginal, and
unacceptable, (subnominal) conditions are
presented. In most cases, however, con-
dition boundaries are not proposed  and
will be developed for future reports.  The
following summarizes the results.

Extent and Geographic
Distribution of Annually
Harvested Herbaceous Crops
  Annually harvested herbaceous crops
are planted on about 1.68 million hectares
and cover some 13% of the total land
area in North Carolina. Crops included in
the Pilot were barley, corn, cotton, hay,
oats,  peanuts, potatoes, rye, soybeans,
sweet potatoes, sorghum, sunflowers, to-
bacco, vegetables (all), and winter wheat.
Information on extent and  distribution of
these crops was obtained  by analyzing
data from the complete NASS JES. Ques-
tions answered include (1) how much land
is cropped?; (2) how diverse  are the state's
croplands?;  (3)  do these cropped areas
tend to be dominated by a single crop?;
(4)  how large are the crop fields?;  and (5)
how do different size fields contribute to
the total  area of annually harvested her-
baceous  cropland? For  example, North
Carolina  fields tend  to be  small,  with a
median field size of just over two hectares
regardless of the type of landscape. Addi-
tionally, half of the total area of annually
harvested herbaceous cropland occurs in
fields smaller than 6.09 hectares.

Crop Productivity
  Two indices of crop productivity are pre-
sented: nitrogen  use efficiency and stan-
dardized  (observed/expected) yield. Ques-
tions  answered are (1) how efficiently is
nitrogen  being used  to produce annually
harvested herbaceous crop? and  (2) is
crop  productivity meeting  expectations
based on soil and climate?
  Nitrogen use efficiency is the ratio of
the amount of nitrogen applied to a field
to the harvested yield from that field. Thus,
the smaller the  number  the greater the
nitrogen use efficiency. Information for cal-
culating this index was obtained from the
EMAP Fall Survey questionnaire. Fifty per-
cent of the land area in North Carolina
cropped to corn, wheat, soybean, and cot-
ton had nitrogen  use efficiencies of 0.029,
0.035, 0.011, and 0.120 or less, respec-
tively. For all seed crops combined, 50%
of the land area planted to these crops in
North Carolina had nitrogen use efficien-
cies of 0.022 or less.
  Standardized yield was calculated in re-
lation to an 11 -year reference period in an
initial attempt to answer the question: how
can data from  different crops be brought
together in  a single  productivity index?
The eventual goal is to answer the ques-
tion: is crop productivity meeting expecta-
tions based on  soil and climate? If ob-
served and expected yields are the same,
standardized yield has a value of 1.0; if
observed yields are greater than expected,
the index has a  value greater than  1.0;
and if observed  yields are less than ex-
pected, the  index has a value less than
1.0. The median value  for all the observed/
expected indices presented is greater than
1.0. This index presented for a single year
has little meaning; however, over the long
term  this type  of  index  should reflect
changes or trends in overall crop produc-
tivity.

Soil Quality - Physical and
Chemical
  Physical and chemical properties of soils
largely determine and reflect the produc-
tive potential of land.  For the 1992 Pilot,
we  analyzed composite samples from the
AP  horizon for particle size,  organic mat-
ter, cation exchange  capacity, selected
micro- and macronutrients, and  some con-
taminants related  to  sludge application.
Questions posed include (1) do soils have
acceptable amounts of clay to sustain crop
production?;  (2) do the soils have accept-
able levels of organic matter in  order to
provide  aeration to the  roots  and retain
nutrients?; (3) do soils  have pH levels that
facilitate the availability of essential plant
nutrients?; (4) do the soils have cation
exchange capacities that enable nutrient
storage  and  supply?; (5) do the soils have
adequate  plant available phosphorus to
sustain plant growth?;  and (6) do the soils
have  lead or cadmium  levels  that pose
health risks to the ecosystem?
  As an example, ranges of 18-35% clay
content  and organic  matter content of
greater than 1 %  are proposed  as accept-
able  levels  to promote growth  of crop
plants. Based upon these criteria, the pro-
portion of  land cropped with annually har-
vested herbaceous crops that  have soils
with acceptable levels  of clay and organic
matter for growth of crop plants is 0.36 in
the  Piedmont, 0.10 in the Coastal Plain,
and 0.30 for the state as a whole.

Soil Biotic Diversity
  Biotic communities  in  soil are  respon-
sible for the decomposition of organic mat-
ter,  are  involved in many aspects of nutri-
ent  cycling,  provide mechanisms  for  the
development of pore  spaces within soil,
and interact with plant  roots. The status of

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the soil biota is vital to the overall charac-
terization of soil condition or health.
   Nematodes may serve as a good indi-
cator of soil condition because they are
diverse in their feeding habits and occur
as central members of the soil food web.
A highly stable or mature  community  of
nematodes would indicate minimal distur-
bance or contamination of the soil biota.
Questions answered in the Pilot included
(1) what is the degree of stability or matu-
rity in nematode communities in soil? and
(2) what is the degree of diversity of nema-
todo communities in soil?
   For land cultivated in annually harvested
herbaceous crops in  the Piedmont and
Coastal  Plain regions of North Carolina,
only a small proportion of communities of
soil nematodes had a relatively  high de-
gree of stability or maturity. The propor-
tion of land area  cultivated with  annually
harvested herbaceous crops having val-
ues for the maturity index for free-living
nematodes of less than 3.2 on a 1-5 scale
(where 5 is  the  most  mature  or stable
community) was estimated  to be  0.95. A
higher proportion of larger values (>3.0)
was found for soils in the Piedmont than
in the  Coastal Plain region for both free-
living  and  plant-parasitic  nematodes.
Trophic  diversity  values had a  greater
range in the Piedmont than in the  Coastal
Plain with higher index values occurring in
the Piedmont.

Water Quality
   Water is essential to any agroecosystem,
and  it  carries  materials from  the
agroecosystem  into the  larger landscape.
Ponds and wells were sampled during the
fall sample of the Pilot, and water samples
were analyzed for two types of contami-
nants:  nitrates and pesticides. Questions
addressed include (1) what is the distribu-
tion of nitrate concentrations in wells on
farms in North Carolina?; (2) what is the
distribution of nitrate concentrations in farm
ponds  in North Carolina?; and  (3)  how
extensive is  pesticide  contamination  of
farm ponds and wells in North Carolina?
   For wells, the EPA  maximum contami-
nant level for water is 10 ppm  nitrate-N.
From the Pilot data, an estimated 3.5% of
wells had greater than 10 ppm nitrate-N,
and the median  concentration was ap-
proximately  1 ppm. The maximum con-
centration detected was  19 ppm nitrate-N.
In farm ponds, concentrations of nitrate-N
were generally  less than those found  in
wells with a median concentration of 0.2
ppm, A spectrum  of  12  insecticides/
nematicides and herbicides  was  not de-
tected above the one part per billion thresh-
old in any sample fronvwells or ponds.

Agrichemical Use
   Fertilizers  and pesticides are  integral
components in the production  of crops in
agroecosystems. Applications of materi-
als in both of these agrichemical catego-
ries can result in both positive and nega-
tive effects on the biological components
of agricultural systems. A preliminary ques-
tion addressed in the Pilot was how much
stress is put on the ecosystems of North
Carolina by applying chemical fertilizers
and pesticides?
   Extent of use of agrichemicals  may be
one indication of potential stress placed
on agricultural systems. As an example,
extent of use of four materials was con-
sidered: the  herbicide  atrazine; the  bio-
logical  control  agent Bt or  Bacillus
thuringiensis (used against insect pests);
the insecticide/nematicide carbofuran; and
the commercial fertilizer nitrogen. Atrazine,
Bt, carbofuran, and fertilizer nitrogen were
applied  at least once to 17.8, 0.8, 2.1, and
75.5% of the  land area of annually  har-
vested  herbaceous  crops  in North Caro-
lina. Atrazine  was applied an average of
1.06 times and fertilizer nitrogen an aver-
age of 1.72 times per year.

Evaluation of Designs,
Indicators, and Activities
   Design comparisons were  performed
primarily for fall  questionnaire and  soil
sample  data.  Only statewide  estimates
were used  and the comparison was done
both accounting for and ignoring stratifica-
tion by  intensity of agricultural use, which
was provided  by NASS. The efficiency of
one design relative to  another was de-
fined as the ratio of the variances for the
statistic of  interest,  adjusted for different
sample  sizes when  necessary. A relative
efficiency greater than  one indicates  that
the Hexagon  Design  is  more efficient,
whereas a relative efficiency less than one
indicates that the Rotational Panel Design
is  more efficient. For eight measures  of
soil quality (physical and  chemical)  and
two measures of crop productivity,  ac-
counting for stratification,  the Rotational
Panel Design  was more efficient in eight
cases and the Hexagon design was more
efficient in two cases. When relative  effi-
ciency was calculated with cost included
as a factor, the Rotational Panel Design
was always the more efficient design.
  Successes and challenges in indicator
development and evaluation were specific
to  the  indicator considered.  In  general,
indicators performed well; however,  the
suite of indicators is not  yet  sufficiently
well developed to fully assess the ecologi-
cal condition of  agricultural systems. For
assessing crop productivity, one challenge
is how to successfully bring together dif-
ferent  crops into  a single, interpretable
productivity index. For assessing soil qual-
ity, the challenge is to develop a single,
interpretable index that incorporates the
key physical, chemical, and biological fac-
tors of soil health. For assessing the ex-
tent and  geographic distribution of annu-
ally harvested herbaceous crops, one chal-
lenge is to provide a clear interpretation of
crop diversity or  land use diversity indices
that can  be calculated. For agrichemical
use, a challenge  is how to integrate EMAP-
Agroecosystems data with information al-
ready collected by other federal agencies.
Another challenge for all indicators is to
quantify the frequency and magnitude of
measurement errors.
  Activities in all areas of the Pilot were
generally successful. The interactions with
NASS personnel were very successful with
NASS personnel involved in four areas of
the Pilot: (1) collecting data  during their
regular JES; (2) drawing  the sample of
fields to be visited in the fall; (3) designing
and conducting the fall questionnaire; and
simultaneously (4) collecting fall soil and
water samples. The Pilot was generally a
logistical  success. Questionnaire  perfor-
mance and survey administration, soil sam-
pling, water sampling, shipping and sample
tracking,  laboratory relations,  and  report-
ing back to respondents generally occurred
in a satisfactory  manner. The quality as-
surance  (QA) aspects of the  Pilot pro-
ceeded in two components as planned.
NASS has a well-established QA program
and EPA personnel performed successful
field audits during data collection and labo-
ratory audits during sample analysis. With
regard to information  management, the
primary goal—to develop  a cooperative,
working  relationship with NASS—was
achieved. Extensive discussions within the
ARG and with personnel in partner agen-
cies have been held to review Pilot activi-
ties, and lessons learned will contribute to
the success  of future efforts.

Conclusions
  The  1992  Pilot in North Carolina pro-
vided an  initial test of the concepts relat-
ing to design, sampling,  indicator devel-
opment, data analysis, quality assurance,
logistics,  and information management. A
preliminary comparison of  the  efficiency
of two  sampling frames or designs was
made. An initial suite of indicators for the
extent and distribution of  cropland, crop
productivity, soil quality, water quality, and
agrichemical  use was evaluated with re-

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spect to the ability of indicators to address
assessment questions;  the  spatial  vari-
ability of indicator values within and among
sample units; the usefulness of each indi-
cator in  determining condition;  and the
cost-effectiveness of each indicator. Plans
for sampling; logistics; quality assurance;
data analysis, summarization, and report-
ing;  and information management were
made,  carried out, and  evaluated. The
information obtained from  the  Pilot will
 allow  the  ARG to continue to evaluate
 and develop the program components es-
 sential for the eventual implementation of
 regional and national monitoring programs
 to  assess the condition of the Nation's
 agricultural systems.
-   This research was funded primarily  by
 the U.S. Environmental Protection Agency
 (EPA) through its  Office of Research and
 Development   under  Interaqency  Agree-
 ment Nos. DW12934170 with the U.S. De-
partment of Agriculture, Agricultural  Re-
search Service, and DW1293747 with the
USDA National Agricultural Statistics Ser-
vice.  It was conducted  by our research
partners under the management of the En-
vironmental Monitoring Systems Laboratory,
Las Vegas, in support of the Environmental
Monitoring and Assessment Program.
                                                                      •&U.S. GOVERNMENT PRINTING OFFICE: 1994 - 55O-M7/80270

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 C. Lea CampbalUs with the USDA Agricultural Research Service, Raleigh, NC
   27606; Jeff M. Bay, Karen £ Nauman, Kurex Sidik, David W. Turner, Anne S.
   Hellkamp, George R. Hess, MichaselJ. Munster, Deborah A. Neher, Steven L.
   Peck, and Mark B. Tooley are with North Carolina State University, Raleigh,
   NC 27695; GailL Olsen is with EG&G Idaho, Inc., Idaho Falls, ID 83415; and
   the EPA author, Brian A. Schumacher, is with the Environmental Monitoring
   Systems Laboratory,  Las Vegas, NV 89193-3478.
 Susan E. Franson is the EPA Project Officer (see  below).
 The complete report, entitled "Environmental Monitoring and Assessment Program:
   Agroecosystem Piht Field Program Report - 1992," (Order No. PB94-179 819
   Cost: $27.00, subject to change) will be available only from:
         National Technical Information Service
         528S Port Royal Road
         Springfield, VA 22161
         Telephone: 703-487-4650
 The EPA Project Off her can be contacted at:
         Environmental Monitoring Systems Laboratory
         U.S. Environmental Protection Agency
         Las Vegas, NV 89193-3478
United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268

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