County-level Cropland Carbon Estimates for the Contiguous U.S., 1990-2005

 

Method of Estimation

 

The United Sates Department of Agriculture (USDA), National Agricultural Statistics Survey (NASS) produces estimates of crop yields per county per year.  These yield estimates can be converted to carbon by converting units reported by NASS to one standard unit (kg), converting to dry matter, and multiplying by a carbon content factor of 0.4 (Brady and Weil, 1996).  Yield estimates can be divided by the harvest index to estimate total above-ground biomass.  Multiplying aboveground biomass with the root:shoot ratio provides an estimate of below-ground biomass.  Finally, summing above- and below-ground biomass provides an estimate for total net primary productivity (NPP).    This method follows approaches used by Prince et al. (2001), Hicke and Lobell (2004), and Hicke et al. (2004).  Factors used in our estimations are provided in Table 1.

 

Table 1. Factors used to estimate NPP-carbon for U.S. crops.

Crop

Reporting units

mass per unit (kg)

Conversion to Dry matter

Harvest Index

Root:shoot ratio

corn grain

bushel

25.4

0.87

0.53

0.18

corn silage

ton

907.2

0.26

1.00

0.18

soybean

bushel

27.2

0.92

0.42

0.15

oats

bushel

14.5

0.92

0.52

0.40

barley

bushel

21.8

0.90

0.50

0.50

wheat

bushel

27.2

0.89

0.39

0.20

sunflower

pound

0.453

0.93

0.27

0.06

hay

ton

907.2

0.85

1.00

0.87

sorghum grain

bushel

25.4

0.87

0.44

0.08

sorghum silage

ton

907.2

0.26

1.00

0.18

cotton

bale

217.7

0.92

0.40

0.17

rice

hundredweight

50.8

0.91

0.40

0.46

peanuts

lbs

0.45

0.91

0.40

0.07

potatoes

hundredweight

50.8

0.20

0.50

0.07

sugarbeets

ton

907.2

0.15

0.40

0.43

sugarcane

ton

907.2

0.70

0.70

0.18

tobacco

lbs

0.453

0.80

0.60

0.80

rye

bushel

25.4

0.90

0.50

1.02

beans

hundredweight

50.8

0.76

0.46

0.08

 

 

Our final results are provided as carbon in net primary productivity (NPP), aboveground biomass (AgB), belowground biomass (BgB), harvested and removed biomass (Harvest), and surface residue remaining following the harvest (Residue).  All units are in Mg C yr-1.  The following NASS commodity codes are represented in our analysis: 11199199, 15499199, 11299999, 11399999, 10199999, 15831999, 18999999, 19599999, 11499199, 12121999, 10619999, 15399199, 39199999, 39299999, 13299199, 13199199, 14133699, 14133599, 14133799, 14133199, 14255599, 14244199, 14122299, 14122399, 14111299, 14111399, 14111199, 10499999, 16199999, 30429929.  These represents all crops in Table 1 including subcategories of tobacco and beans.

 

References

Brady, N.C. and R.R. Weil. 1996. The nature and properties of soils. 11th edition. Prentice-Hall, Inc., Upper Saddle River, New Jersey.

Hicke, J.A. and D.B. Lobell. 2004. Spatiotemporal patterns of cropland area and net primary production in the central United States estimated from USDA agricultural information. Geophysical Research Letters 31, L20502, doi:10.1029/2004GL020927,2004.

Hicke, J.A., D.B. Lobell, and G.P. Asner. 2004. Cropland area and net primary production computer from 30 years of USDA Agricultural Harvest Data. Earth Interactions 8, Paper No. 10.

Prince, S.D., J. Haskett, M. Steininger, H. Strand, and R. Wright. 2001. Ecological Applications 11(4): 1194-1205.

 

File formats and Processing

  1. Comma Delimited (CSV)
  2. ArcGIS Shapefile (SHP)

      Geographic coordinate system name: GCS_Assumed_Geographic_1

      Geographic coordinate units: decimal degrees

      Horizontal Datum Name: North American Datum of 1927

      Ellipsoid Name: Clarke 1866

      Semi-major Axis: 6378206.400000

      Denominator of Flattening Ratio: 294.978698

      Bounding coordinates

                  Horizontal

                              In decimal degrees

                                          West: -178.225250

                                          East: -66.950474

                                          North: 71.383102

                                          South: 18.913826

                              In projected or local coordinates

                                          Left: -178.225250

                                          Right: -66.950474

                                          Top: 71.383102

                                          Bottom: 18.913826

 

3. Data location: http://cdiac.ornl.gov/

 

4. Data set author:

Tristram O. West

Environmental Sciences Division

Oak Ridge National Laboratory

P.O. Box 2008

Oak Ridge, TN 37831-6335

865-574-7322

westto@ornl.gov