United States
Environmental Protection
Agency
National Exposure
Research Laboratory
Las Vegas NV 89193-3478
Research and Development
EPA/620/SR-95/004 July 1995
4>EPA Project Summary
Environmental Monitoring and
Assessment Program
Agricultural Lands Pilot Field
Program Report—1993
This document provides a compre-
hensive report on the EMAP Agricul-
tural Lands 1993 Pilot Field Program,
which was conducted in Nebraska. Re-
sults of the pilot monitoring effort are
presented on land use and cover, crop
productivity, and soil quality (physical,
chemical, and biological). Other aspects
of the pilot study are also addressed
including design and sampling, indica-
tor evaluations, logistics, quality as-
surance and information management.
This Project Summary was developed
by EPA's National Exposure Research
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 Project Report
ordering information at back).
Introduction
The Environmental Monitoring and As-
sessment Program (EMAP) is being de-
signed to help policy makers decide how
to allocate limited resources among envi-
ronmental problems. Many monitoring ef-
forts are site- or problem-specific and do
not allow assessment of condition over
large regions with statistical confidence.
EMAP will track the condition of our envi-
ronment on a regional basis.
The mission of EMAP's Agricultural
Lands Resource Group (ARC) is to de-
velop and implement a program that will,
in the long term, monitor and assess the
condition and extent of the nation's agri-
cultural lands. The specific objectives are
to
Estimate status and trends in con-
dition.
Estimate geographic coverage and
extent.
Seek stressor-condition associa-
tions.
Provide summaries and assess-
ments.
The ARG conducted its second Pilot
Field Program in Nebraska in 1993. There
were three major objectives: (1) test a
suite of indicators in these categories: land
use and cover, crop productivity, and soil
quality; (2) compare the relative efficiency
of two sampling designs; (3) develop and
refine plans for key components of the
monitoring program.
Nebraska was selected primarily be-
cause of the presence of both typical
midwestern intensively cropped lands and
western sparsely cropped lands. Address-
ing ecological condition in widely varying
settings is crucial for developing a suite of
indicators that can be used nationally.
EMAP uses probability sampling frames
to choose sample sites, allowing statisti-
cally valid statements to be made for a
region. Two different frames were used;
288 sites in Nebraska were chosen, all
planted to annually harvested herbaceous
crops (AHHCs). After the 1993 fall har-
vest, data were collected on crop yields,
soil characteristics, and management. In
addition, data on land use and cover were
provided from the National Agricultural Sta-
tistics Service's June Agricultural Survey.
Land Use and Cover
AHHCs are planted on over 7.4 million
ha in Nebraska, covering 37% of the state.
Most are found in the extensively culti-
vated lands in eastern and southern Ne-
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braska; western Nebraska is predominantly
rangeland that is sparsely cropped. Corn
is the most common crop (45% of crop-
land); soybeans are the second most com-
mon crop (14%).
Crop diversity was measured as the
number of different crops in a given area
and their relative abundance. In the ex-
tensively cropped lands, one third of the
sample areas (260 ha each) contained
four crops; in half the areas, a single crop
(usually corn) accounted for more than
55% of the total cropped acreage. How
diversity changes with time will be of in-
terest: decreasing diversity would signal
increasing vulnerability to pests and dis-
eases.
Approximately 75% of all fields in
Nebraska's extensively cropped lands are
16 ha or smaller; this differs from the
usual impression of Nebraska as a state
covered by large fields. Approximately 35%
of the extensively cropped lands are cov-
ered by fields in this size range.
There are nearly 75,000 farm ponds in
Nebraska, covering almost 58,000 ha.
More than half are less than 0.3 ha in
area. Water for livestock is the single larg-
est use of farm ponds, followed by ero-
sion and flood control.
Crop Productivity
Is cropland producing the yields we ex-
pect? We calculated the ratio of the yield
reported for each sample field to the county
average yield for that crop over the period
1980-1989 (irrigated fields compared to
the average for irrigated fields; nonirrigated
compared to nonirrigated). For the five
predominant crops, 1993 was slightly bet-
ter than average; soybeans did better than
corn or sorghum.
Is cropland requiring increasing subsi-
dies of nonrenewable inputs? We exam-
ined nitrogen use efficiency by calculating
the quantity of nitrogen applied for each
unit of harvested material. Not only soy-
beans (a legume) but also wheat shows
more efficient use of applied nitrogen than
the predominant crop, corn.
Are crops being managed for plant
health? We examined crop rotation in three
ways.
(1) Rotation plans. We estimate that
nearly half of the AHHC land in Nebraska
is not covered by any planned rotation; of
the land in rotation, half the plans are two
years in length. (2) How long since the
1993 crop was grown in that field? Over
half the AHHC land had the same crop in
1993 as in 1992, and 72% of the corn
acreage had been planted to corn in 1992.
This is a substantial lack of rotation for a
crop that occupies half of the AHHC acres
in Nebraska. (3) How many crops were
grown in the past three years? Forty-two
percent of the AHHC land had the same
crop every year out of three; corn again
predominated.
Soil Quality
Surface soil samples were analyzed for
a set of physical, chemical, and biological
indicators. Median values for clay, organic
carbon, and cation exchange capacity are
lowest in northwestern and highest in east-
ern Nebraska; median pH values follow
an opposite trend, with the highest in the
northwest. An integrated rating showed
better quality surface soils in eastern and
southern Nebraska than in the northwest.
This pattern corresponds to the trend in
land use, with most cultivated land in the
eastern part of the state.
A maturity index for free-living nema-
todes, which reflects the degree of stabil-
ity of soil biota, showed that the relative
health of the eastern and southern re-
gions of Nebraska was similar, as did the
Shannon index of trophic diversity. A ma-
turity index for plant-parasitic nematodes
showed healthier soils in the east, although
its interpretation is controversial.
Soil pits were dug at 26 sites to exam-
ine subsurface indicators. Two methods
for assessing soil quality, the Soil Rating
for Plant Growth (SRPG) and the Soil
Quality Report Card, underwent prelimi-
nary development using these data. Al-
though different in their approaches, both
provide ways of determining whether soils
are meeting their potential. The SRPG will
be best used for regional monitoring,
whereas the Report Card will be more
suitable for monitoring specific sites.
Future Directions
The ARG will continue to develop indi-
cators for use in a national monitoring
program. This includes further work on
the indicators explored here, development
of new indicators (we are testing an insect
indicator in 1994), and consideration of
pasture-livestock systems, windbreaks,
and other components of the agricultural
landscape. In addition, we will address
cross-resource issues by working with
other EMAP Resource Groups in the mid-
Atlantic region in 1994-1997. We are also
expanding our partnerships with other fed-
eral agencies, primarily USDA's National
Agricultural Statistics Service and Natural
Resources Conservation Service.
EMAP continues to play an important
role in the national effort to base environ-
mental policy decisions on sound scien-
tific information. The monitoring and
assessment techniques being developed
by EMAP are intended to form the basis
for any regional or national monitoring ef-
fort where determining the nature and
scope of environmental problems is of in-
terest.
This research has been funded by the
United States Environmental Protection
Agency (EPA) through its Office of Re-
search and Development under Inter-
agency Agreements #DW12934170 with
U.S. Department of Agriculture (USDA),
Agricultural Research Service (ARS),
#DW12934747 with the USDA National
Agricultural Statistics Service, and
#DW12936168 with the USDA Natural
Resources Conservation Service, and by
the USDA ARS. It was conducted with our
research partners under the management
of the Characterization Research Division
of the National Exposure Research Labo-
ratory in support of the EMAP Program.
Neither U.S. EPA nor USDA ARS en-
dorses or recommends any trade name or
commercial product mentioned in the full
document to the exclusion of others. They
are mentioned solely for the purpose of
description or clarification.
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Susan E. Franson is the EPA Project Officer (see below).
The complete report, entitled "Environmental Monitoring and Assessment Program,
Agricultural Lands Pilot Field Program Report—1993, "(Order No. PB95-243069;
Cost: $19.50, subject to change) will be available only from
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at
National Exposure Research Laboratory
U. S. Environmental Protection Agency
Las Vegas, NV 89193-3478
United States
Environmental Protection Agency
National Risk Management
Research Laboratory (G-72)
Cincinnati, OH 45268
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