Originally
published Vol. 2, Issue 5 (November 2004)
Estimating U.S. Cropland
Area
Marlow Vesterby, Kenneth S. Krupa, Ruben
N. Lubowski
Measuring cropland area is essential
for assessing the economic and environmental performance
of U.S. agriculture. ERS tracks cropland in its
annual “cropland used for crops” data
series, which began in 1910. Cropland used for crops
is the sum of cropland harvested, crop failure,
and summer fallow. (Total cropland is part of the
ERS Major Land Use series, started in 1945, that
accounts for all land use in the 50 States.)
The data behind the ERS cropland
series come from the Crop Production Annual Summary
published by USDA’s National Agricultural
Statistics Service (NASS). This survey includes
harvested acres of principal crops, the predominant
field crops in U.S. agriculture. In 2005, 21 principal
crops accounted for almost 98 percent of all harvested
crop acreage in the United States, but just four
crops—corn, soybeans, wheat, and hay—accounted
for about 82 percent of all cropland harvested acreage.
The acreages of other crops (fruits
and nuts, vegetables, and minor crops), which are
published every 5 years by the U.S. Census of Agriculture
and change little from one census year to the next,
are added to the acres of principal crops to derive
total crops harvested. In 2002, “other crops”
comprised over 40 other crops plus nursery and greenhouse
products. While these crops take up relatively little
acreage, they can account for large market value
shares of sales.
The Crop Production Annual Summary
report counts all acres harvested, including double
cropping. However, each cropland acre can only be
counted once; thus, double cropping is subtracted
from total crops harvested because cropland used
for crops becomes part of the ERS Major Land Use
series, which must sum to total U.S. land area.
The result is total cropland harvested. Most double
cropping occurs when soybeans are planted after
the harvest of small grains (mainly wheat) in the
same year, and these estimates are from the annual
NASS acreage report published in June. Smaller acreages
of other crops are also double cropped, and these
estimates are from the Census of Agriculture.
Crop failure is the difference
between cropland planted and cropland harvested.
However, some cropland planted is not intended to
be harvested. Thus, adjustments are made to account
for cover crops, crops grazed, and crops cut for
hay. Data for these adjustments are from the Crop
Production Annual Summary and the Census.
Cultivated summer fallow occurs
predominantly in the Great Plains where it is a
practice used to conserve moisture and control weeds.
Fields are typically planted and harvested one year
and summer fallowed the next. Acreage estimates
are obtained from NASS, the Census of Agriculture,
or the Conservation Technology Information Center.
When no data are available, ERS estimates the area
of cultivated summer fallow based on the acreage
of wheat in the major summer-fallow States. The
use of summer fallow has slowly declined over the
last 30 years, due mostly to the increased adoption
of conservation tillage and herbicides, which reduce
the need for summer fallow to conserve moisture
and control weeds.
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