The Geography of Soil Color
Maps, Educational Narratives, and Database Describing
the Soil Colors of the Continental United States
D.E. Beaudette
C.A. Ferguson
J. Nemecek
USDA-NRCS
Soil and Plant Science Div.
Acknowledgments &
Data Sources
• Charles Ferguson and Jason Nemecek
• Dr. Cynthia Stiles and Drew Kinney
• 100+ years of soil survey efforts
• Curation of 23,798 Official Series Descriptions
• SSURGO, the 1:24k detailed soil survey of the U.S.A.
• Dr. A.T. O’Geen: supported early efforts, pre-publication
• R color conversion functionality (grDevices, farver)
• 2005: Pinnacles National Monument soil survey
• 2009: SoilWeb OSD sketches with color (c/o T. Reinsch)
• 2011: OSD color database
• 2011: automated color conversion -- aqp::munsell2rgb()
• 2013: morphologic data added to soilDB::fetchKSSL()
• 2014: STATSGO soil color map (Z. Libohova & S. Peaslee)
• 2018: SSURGO soil color map (C. Ferguson & J. Nemecek)
Why?
• Soils are complex–we know this, but don’t (can’t?)
always deliver a compelling narrative.
• It is hard to conserve what you don’t understand.
• It is hard to understand what you don’t perceive.
• Make soil properties / processes real.
When put into context, soil color tells a great story.
Soil Color
Ash Basalt Granodiorite Mixed Sedimentary Mafic Lahar Andesitic Lahar
Liles, G. C., D. E. Beaudette, A. T. O’Geen, and W. R. Horwath. 2013.
Developing predictive soil C models for soils using quantitative color measurements. Soil Sci. Soc. Am. J. 77:2173-2181
Soil Color
Photos c/o G.C. Liles, I. Ainuddin, A. Conlin
Pigments
10YR 2/1 10YR 2/1 10YR 2/1 10YR 2/1 2.5YR 4/6
humus todorokite pyrite iron sulfide lepidocrocite-fine
10R 4/8 2.5YR 3/4 2.5YR 3/6 5R 3/6 10YR 6/1
hematite-fine maghemite ferrihydrite hematite-coarse quartz
5Y 6/4 7.5YR 6/6 5YR 6/8 5Y 5/1 7.5YR 5/6
jarosite akaganeite lepidocrocite-coarse glauconite goethite-fine
10YR 7/8 10YR 8/3 10YR 8/2 10YR 8/2 10YR 8/6
schwertmannite gypsum dolomite calcite goethite-coarse
http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/edu/?cid=nrcs142p2_054286
U. Schwertmann, 1993. SSSA Special Publication no. 31, pages 51--69
Colors from the OSDs
A--0.5 to 2 inches. (1 to 5 cm); reddish brown (5YR 5/4) gravelly
loam. reddish brown (5YR 4/3) moist; 17 percent clay; moderate
fine subangular blocky parting to moderate fine granular
structure; hard. friable. nonsticky. slightly plastic; common very
fine roots; many very fine irregular pores; 20 percent
subangular metavolcanic gravel; moderately acid. pH 6.1 by
Hellige-Truog; abrupt wavy boundary. (1 to 3 inches. (3 to 8 cm)
thick)
5YR 5/4 5YR 4/3 aqp::parseMunsell()
soilDB::fetchOSD()
BONNEAU CECIL LEON
0 cm
A A
Ap
E1
Eg1
Eg2
E2
Bt1 Bh1
Bh2 50 cm
Bt1 Bw/Bh
Eg/Bh
Bt2 Bt2
E'g
100 cm
Bt3 BC
B'h 150 cm
Bt4 C
200 cm
B'w/B'h
250 cm
300 cm
photos: John A. Kelley soilDB::fetchOSD()
Gap-filling: Art and Science
SSURGO → STATSGO
organic horizons w/out color → Oi, Oe: 7.5YR 2/2 Oa: 10YR 2/1
rock outcrop → grey
missing data → GIMP “heal selection”
Results
Moist soil colors, available as: PNG, animated GIF, GeoTiff, web-maps
25cm | 2014 STATSGO 1:250,000
25cm | 2018 SSURGO 1:24,000
25cm | Leon: Sandy, siliceous, thermic Aeric Alaquods
photo: John A. Kelley
25cm | Cecil: Fine, kaolinitic, thermic Typic Kanhapludults
photo: John A. Kelley
25cm | Bonneau: Loamy, siliceous, subactive, thermic Arenic Paleudults
photo: John A. Kelley
One spatially consistent pattern of soils in
California is the red soil zone. This area
extends in north-south direction across
most of the Sierra Nevada Foothill Region
and into the lower elevations (< 1500 m)
of the Sierra. These red soils have large
amounts of secondary iron oxides such as
hematite. In the foothills these intensely
weathered soils are derived from iron
rich parent rocks such as basalt,
greenstone, gabbro, serpentinite, and
mafic phases of granitic rocks. In the low
elevations of the Sierra Nevada (just
below the rain-snow transition) intense
weathering due to favorable climatic
conditions is believed to be the main
factor causing the expression of this soil
color.
Coming Soon
• Version 2.0: component-specific colors (linked pedons)
• HI, AK, US territories
• Soil Color database:
• OSD colors
• Curated pedon data, by soil series
• Quantitative RIC via CIE LAB coordinates
• Color-based queries and similarity
Thank You
Soil Colors of the Continental United States
https://goo.gl/kpL8LV
Exploring Soil Colors (WI State Parks)
https://goo.gl/1hBMux
AQP Website
http://ncss-tech.github.io/AQP/
Soil Color in R (KSSL + morphologic data)
https://goo.gl/uWQBah
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