Glossary
Definitions, sources of data, and estimation techniques have
varied little over time in the Major Land Uses (MLU) series. The
following definitions and explanations of the data are for the most
recent year, but generally apply to all previous years as well.
Estimates of major land uses for 2007 are the latest in a series
of land use inventories based on available statistics conducted by
the Economic Research Service (ERS) and its predecessor agencies
within the United States Department of Agriculture (USDA). This
series, which began in 1945, is comparable in categories and area
coverage. Part of the series,
Cropland used for crops 
, is
consistent back to 1910 on a yearly basis. These periodic
inventories are useful because even though numerous public agencies
develop land use data, no other single agency, except ERS, accounts
for the use of all land (public and private for all 50 States) in
the United States. The inventories provide benchmarks for
understanding changes in the supply and demand for land in
different uses.
The estimates, with few exceptions, were constructed from
available data, rather than compiled and used exactly as developed
by source agencies. The data are typically obtained from censuses
and surveys differing greatly in scope, methods, definitions, and
other characteristics. The individual sources account for only a
few uses and for only a limited part of the total land area. The
available data contain conflicts and overlaps that must be
reconciled or removed.
Definitions
Cropland-Total cropland includes five
components: cropland harvested, crop failure, cultivated summer
fallow, cropland used only for pasture, and idle cropland. The
estimate of total cropland in 2007 included total cropland as
reported by the 2007 Census of Agriculture (USDA/NASS, 2009) plus
an upward adjustment to conform to data on principal crops
harvested in each State as reported by the National Agricultural
Statistics Service for 2007 (USDA/NASS, 2010). In 2007, the census'
estimate of total principal crops harvested was about 98 percent of
the estimate for the same crops from NASS.
The Census of Agriculture data is derived from a census of all
farm operations that produce, or normally would produce and sell,
$1,000 or more of agricultural products annually. USDA's NASS
undertakes extensive procedures to include all eligible farms in
the census. The census was conducted through mailings and, to a
lesser extent, telephone or personal enumeration with a goal of
achieving at least a 75-percent response rate in all counties.
Missing data were calculated from responses to other surveys or
imputed from reporting farms of a like type. The response rate for
the 2007 Census of Agriculture was 85.2 percent, compared with 88.0
and 86.2 percent for the 2002 and 1997 Censuses, respectively.
Details on the methodology and reliability of estimates are
contained in Appendix A of the 2007 Census of Agriculture
(USDA/NASS 2009a).
The components of cropland are:
Cropland used for crops-Three
of the cropland acreage components-cropland harvested, crop
failure, and cultivated summer fallow-are collectively termed
cropland used for crops, or the land input to crop production.
Annual estimates of cropland harvested are based on both census
data and the series on principal crops harvested as maintained by
NASS. Annual estimates of crop failure are based on differences in
planted and harvested acreage of principal crops from the NASS data
series. Annual estimates of cultivated summer fallow historically
have been based on fragmentary data from a variety of sources.
Since the late 1970s, the estimates have been based on data from
the Census of Agriculture and unpublished NASS data.
Cropland harvested-Includes
row crops and closely sown crops; hay and silage crops; tree
fruits, small fruits, berries, and tree nuts; vegetables and
melons; and miscellaneous other minor crops. In recent years,
farmers have double-cropped about 4 percent of this acreage.
Crop
failure-Consists mainly of the acreage on which crops
failed because of weather, insects, and diseases, but does include
some land not harvested due to lack of labor, low market prices, or
other factors. Crop failure is calculated using the difference
between cropland planted and cropland harvested. However, some
cropland planted is not intended to be harvested. Thus, the acreage
planted to cover and soil improvement crops not intended for
harvest is excluded from crop failure and is considered idle. In
recent years, crops have failed on about 2-3 percent of the acreage
planted for harvest.
Cultivated
summer fallow-Refers to cropland in subhumid regions of
the West that are cultivated for one or more seasons to control
weeds and accumulate moisture before small grains are planted. This
practice is optional in some areas, but it is a requirement for
crop production in the drier cropland areas of the West. Other
types of fallow, such as cropland planted to soil improvement crops
but not harvested and cropland left idle all year, are not included
in cultivated summer fallow but are included as idle cropland.
Cropland pasture-Generally is
considered to be in long-term crop rotation. This category includes
acres of crops hogged or grazed but not harvested and some land
used for pasture that could have been cropped without additional
improvement. Cropland pastured before or after crops were harvested
was included as harvested cropland and not cropland pasture.
Estimates in this land-use category are derived from the census of
agriculture (USDA/NASS, 2009).
Idle
cropland-Includes land in cover and soil-improvement crops
and cropland on which no crops were planted. Some cropland is idle
each year for various physical and economic reasons. Acreage
diverted from crops to soil-conserving uses (if not eligible for
and used as cropland pasture) under Federal farm programs is
included in this component. Cropland enrolled in the Federal
Conservation Reserve Program (CRP) and Wetlands Reserve Program
(WRP) is included in idle cropland.
Grassland pasture
and range-Grassland pasture and range encompass all open
land used primarily for pasture and grazing, including shrub and
brushland types of pasture, grazing land with sagebrush and
scattered mesquite, and all tame and native grasses, legumes, and
other forage used for pasture or grazing--regardless of ownership.
Because of the diversity in vegetative composition, grassland
pasture and range are not always clearly distinguishable from other
types of pasture and range. At one extreme, permanent grassland may
merge with cropland pasture, or grassland may often be found in
transitional areas with forested grazing land. The estimates in
this report are composites of data from the National Resources
Inventory (NRI), census of agriculture, the Bureau of Land
Management, U.S. Forest Service, and several other Federal agencies
(see definitions for cropland, forested land, special uses, and NRI
for details on the data from these sources). The 614 million acres
classed as grassland pasture and range in 2007 included 409 million
acres in farms (USDA/NASS, 2009a). Also included are estimates of
private grazing land not in farms and public, nonforested grazing
land.
Forest-use
land-A MLU category based on the use of the forest land as
opposed to the forest cover alone. The forest-use category includes
both grazed and ungrazed forests but excludes an estimate of forest
land in parks, wildlife areas, and similar special-purpose uses
from the U.S. Forest Service's inventory of total forest land.
While it is impossible to eliminate overlap with other uses, this
reduced area is a closer approximation of the land that may serve
commercial forest uses as opposed to having forest cover.
Nevertheless, some forest-use land may still be economically
unsuited for timber harvests. In addition, private landowners may
have objectives other than timber harvest. For example, Birch
(1996) found that only 29 percent of private forest owners reported
managing their land primarily for timber production. There are two
components of forest-use land:
Forest land
grazed-Forested pasture and range consisting mainly of
forest, brush-grown pasture, arid woodlands, and other areas within
forested areas that have grass or other forage growth. The total
acreage of forested grazing land includes woodland pasture in farms
plus estimates of forested grazing land not in farms. For many
States, the estimates include significant areas grazed only lightly
or sporadically. The census of agriculture, the NRI, and the U.S.
Forest Service data on active grazing allotments are the principal
sources of data used to develop the MLU estimate (USDA/NASS, 2009;
USDA/NRCS, 2009). Historical data from these and other sources were
useful in developing the 129-million-acre approximation.
Forest land not
grazed-Forest-use land not used for grazing.
Special
uses-Includes rural transportation uses, rural parks and
wildlife areas, farmsteads, and national defense/industrial areas.
Estimates are based on reports and administrative records of the
Census Bureau and Federal and State land management and
conservation agencies.
Rural
transportation uses include highways, roads, railroads,
transportation rights-of-way, and airport facilities outside
Census-defined urban areas.
Rural parks and
wildlife areas include Federal and State parks, wilderness
areas, and wildlife refuges outside Census-defined urban areas.
National defense and
industrial areas include land owned by Department of
Defense and Department of Energy and used for airfields, research
and development, housing, and miscellaneous military uses.
Farmsteads, farm roads, lanes, and
other miscellaneous farmland are included in special uses.
Urban
Areas-Based on the Census Bureau's method for estimating
urban area. This includes urbanized areas with at least 50,000
people and urban clusters with 2,500-50,000 people and excludes
portions of extended cities that are essentially rural in character
and lands in rural residential uses.
Other or miscellaneous
land uses-Includes largely wetlands, rural residential
land, desert, tundra, and other barren land generally of low value
for agricultural purposes that are not independently classified in
the MLU report.
For citations for previous MLU reports and sources for the 2007
data update, see reference citations.