Soil properties data for Counties in the Contiguous United States

Athens, GA 30613-7799]. They worked from a database developed by the Soil Conservation Service (now Natural Resource Conservation Service) [USDA Soil Conservation Service (1985) User manual for interactive soils databases: nation soil survey area database, soil interpretations record database, and plant name database. USDA SCS, Fort Collins, CO].

To find this and similar data now, visit the National Soils Data Access Facility web site: soils.usda.gov/ Our source for the pH data was the Food and Agriculture Organization of the United Nations (FAO) Digital Soil Map of the World and Derived Soil Properties, Version 3.5, Nov. 1995, original scale 1:5 000 000). See [ fao.org/ ] for general FAO information and see [ fao.org/ag/agl/agll/index.stm ] for details on the soils data.

We printed a pH map for the US, overlaid a state boundaries map, and then read off values for each region of each state. The coarse resolution of the map meant that most counties (and even many states) had only a single pH value. High and low values are reported for each county, and represent the range in a particular soil property found in the county.

Many counties have only a single value and it is reported as both the high and the low value. Values are from the database surface soil layer (defined as either 'the plow layer' or 'the A, E, Ab, and EB horizons of the solum'). Values are based only on soils for agricultural lands in the county, not all soils.

EOS-WEBSTER provides seven datasets which provide county-level data on agricultural management, crop production, livestock, soil properties, geography and population. These datasets were assembled during the mid-1990's to provide driving variables for an assessment of greenhouse gas production from US agriculture using the DNDC agro-ecosystem model [see, for example, Li et al. (1992), J. Geophys. Res., 97:9759-9776; Li et al. (1996) Global Biogeochem.

Cycles, 10:297-306]. The data (except nitrogen fertilizer use) were all derived from publicly available, national databases. Each dataset has a separate DIF.

The US County data has been divided into seven datasets. US County Data Datasets: 1) Agricultural Management 2) Crop Data (NASS Crop data) 3) Crop Summary (NASS Crop data) 4) Geography and Population 5) Land Use 6) Livestock Populations 7) Soil Properties