Data Set Citation:
When using this data, please cite the data package:
NCEAS 2017: Prince: Global Primary Production Data Initiative , National Center for Ecological Analysis and Synthesis , and Prince S.
NPP Cropland: Gridded Estimates for the Central U.S.A., 1982-1996
nceas.184.8 (https://knb.ecoinformatics.org:443/knb/metacat/nceas.184.8/nceas)
General Information:
Title:NPP Cropland: Gridded Estimates for the Central U.S.A., 1982-1996
Identifier:nceas.184
Alternate Identifier:crop_npp.xls, crop_npp.txt
Abstract:
Net primary productivity (NPP) of agricultural regions, where most of the land is sown with a few well-studied crops, was estimated from crop harvested yield, as recorded in national agricultural statistics. The magnitudes and inter-annual variations in NPP of croplands in the US Mid-West were estimated using crop area and yield data from the US National Agricultural Statistics Service (NASS). Total NPP, including estimates of both above and below-ground components, was calculated from harvested yield data by (1) conversion from reporting units of yield of the crop product, usually in volume, to mass; (2) conversion from fresh weight to dry weight; (3) estimation of above-ground yield using crop harvest indices, defined as the ratio of economic product (e.g. grain) dry weight to plant above-ground dry weight; and (4) estimation of below-ground yield as a function of above-ground biomass. This approach was applied to corn, soybean, sorghum, sunflower, oats, barley, wheat and hay in Illinois, Indiana, Iowa, Michigan, Minnesota, North Dakota, Ohio and Wisconsin for 1992, and in Iowa from 1982 to 1996. Many counties in these eight states had over 70 per cent coverage of these crops. In Iowa, corn and soybean accounted for over 50 per cent of the land area in most counties. County-level NPP in 1992 ranged from 4 Mg/ha/yr (400 g/m2/yr, dry biomass, or 200 gC/m2/yr in terms of carbon content) in North Dakota, Wisconsin and Minnesota, to over 17 Mg/ha/yr (1700 g/m2/yr, dry biomass, or 850 gC/m2/yr) in central Iowa, Illinois and Ohio. Areas of highest NPP were dominated by corn and soybean cultivation. NPP for counties in Iowa varied between years by a factor of 2, with the lowest NPP in 1983 which had an unusually wet Spring, in 1988 which was a drought year, and in 1993 which experienced floods. A sensitivity analysis, conducted by varying harvest index and root:shoot ratio by 10-50 per cent, indicated that the limit of accuracy of the method is about 1 Mg/ha/yr (100 g/m2/yr, dry biomass).
Keywords:none:
  • net primary productivity (theme)
none:
  • cropland (place)
none:
  • agriculture (theme)
none:
  • U.S. Midwest (place)

Involved Parties

Data Set Creators:
Organization:NCEAS 2017: Prince: Global Primary Production Data Initiative
Organization:National Center for Ecological Analysis and Synthesis
Individual: Stephen Prince
Address:
Department of Geography University of Maryland Room 2181, Le Frak Hall,
College Park, Maryland 20742-8225 USA
Phone:
(301)405-4062 (voice)
Phone:
(301)314-9299 (Fax)
Email Address:
sprince@geog.umd.edu
Data Set Contacts:
Individual: Stephen Prince
Address:
Department of Geography University of Maryland Room 2181, Le Frak Hall,
College Park, Maryland 20742-8225 USA
Phone:
(301)405-4062 (voice)
Phone:
(301)314-9299 (Fax)
Email Address:
sprince@geog.umd.edu
Associated Parties:
Individual: J. Haskett
Individual: Marc Steininger
Individual: H. Strand
Individual: R. Wright
Metadata Providers:
Individual: Andrea Chadden

Data Set Characteristics

Geographic Region:
Geographic Description:U.S. Midwest: Illinois, Indiana, Iowa, Michigan, Minnesota, North Dakota, Ohio, Wisconsin and Iowa. Geographic coordinates are approximate for the area.
Bounding Coordinates:
West:  -102.5  degrees
East:  -77.25  degrees
North:  46.875  degrees
South:  29.875  degrees
Time Period:
Begin:
1982-01-01
End:
1996-01-01

Sampling, Processing and Quality Control Methods

Step by Step Procedures
Step 1:  
Description:

Methods

Crop NPP in the U.S. Midwest states 1992 and State of Iowa (1982-96) used harvested yield statistics provided by the National Agricultural Statistics Service (NASS, Prince et al. 2000). The counties selected for the Midwest states had 50 percent or more land in agriculture and less than 20 percent forest (These thresholds were not applied for temporal analysis in Iowa). The overall approach included i) calculating cropland grain yield based on the NASS data; ii) converting the grain yield to NPP; and iii) estimating the remaining biological yield estimates using harvest indices and shoot:root biomass ration to estimate belowground allocation. County-level data were aggregated to 0.5 degree cell size. NPP values of grid cells crossing county boundaries were calculated with an area weighting method. For Midwest states NPP, only cells completely within the boundary of the study area were included in this report.

Data Set Usage Rights

no restrictions
Access Control:
Auth System:knb
Order:denyFirst
Metadata download: Ecological Metadata Language (EML) File