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.
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.