Iowa Soil Clay Content Maps [gSSURGO]
Author: Meyer Bohn
Clay as a soil separate consists of mineral soil particles that are less than 0.002 mm in diameter. The estimated clay content of each soil layer is given as a percentage, by weight, of the soil material that is less than 2 mm in diameter. The amount and kind of clay affect the fertility and physical condition of the soil and the ability of the soil to adsorb cations and to retain moisture. They influence shrink-swell potential, saturated hydraulic conductivity (Ksat), plasticity, the ease of soil dispersion, and other soil properties. The amount and kind of clay in a soil also affect tillage and earth-moving operations. Most of the material is in one of three groups of clay minerals or a mixture of these clay minerals. The groups are kaolinite, smectite, and hydrous mica, the best known member of which is illite.
Map Details
File Content
The zip file contains the base GeoTIFF soil property rasters, OVR pyramid files (reduced resolution for faster display), AUX auxiliary files (Raster color map, statistics, histogram, table, pointer to pyramid file, coordinate system, transformation, projection information), TFW world files (GeoTIFF coordinate system information), and a LYRX file (stored symbology for viewing in ArcGIS Pro v 2.2 or later) and a LYR file (stored symbology for viewing in ArcGIS for Desktop), and associated metadata in a RTF file.
Metadata – Sources – Limitations
Produced by: Meyer Bohn, Joshua McDanel, and Bradley Miller January (2019)
Created with the gSSURGO mapping toolset for ArcGIS for Desktop 10.6. Available for download at:
https://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/survey/geo/?cid=nrcs142p2_053628
Raster Format: 10-m resolution GeoTIFF, 32-bit floating point
Projection: NAD83 UTM Zone 15N
Extent – West: -96.801571 East: -90.007463 North: 43.644364 South: 40.302683
Soil Survey Staff. 2018. Natural Resources Conservation Service. United States Department of Agriculture. Gridded Soil Survey Geographic (gSSURGO) Database for Iowa. Accessed 27 Oct 2018.
Use limitations: See “Sources of Apparent Error on Existing Soil Maps”. Soil Survey Staff. 2018. Soil Survey Manual – Ch. 4: Soil Mapping Concepts. Natural Resources Conservation Service. United States Department of Agriculture. Available at:
https://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/ref/?cid=nrcs142p2_054254#quality
Scale Range: Not intended for use at scales larger than an order 2 Survey (1:12,000 to 1:31,680).
Available Depths
- 0 – 5 cm • 5 – 20 cm
- 0 – 20 cm • 20 – 50 cm
- 0 – 30 cm • 50 – 100 cm
- 0 – 100 cm • 100 – 150 cm
- 0 – 150 cm • 150 – 200 cm
- 0 – 200 cm