Soil Color

Soil Color
• - it is the property of the soil that depend
on the wavelength of light it reflects or
emits.
• Colors are derived from the color of Fe
oxides and organic matter that coat the
surfaces of soil particles
high OM – Dark color
High Fe oxides- Red to yellow
 SOIL COLOR

– is the most obvious and easily determined

soil characteristic. Although it has little
known direct influence on the functioning
of the soil, color is one of the most easily
determined soil properties and other more
important soil characteristics can be
inferred from soil color.
 Review Question
•N The most visible soil characteristic which
may indicate OM content, parent material
of soil and horizon differentiation
a) soil texture
b) soil structure
c) soil color
d) soil porosity
Measurable variables in color
1. Hue- most dominant spectral color
2. Value – degree of darkness or lightness
(zero is black)
3. Chroma – intensity or brightness (zero is
neutral gray)
Hue - The dominant color
• 10 R is red; 2.5YR has some yellow, 7.5YR are
tans and browns, 2.5 Y is yellow, G is green).
• As soils age they oxidize and change from
yellow to brown to red (e.g., 2.5Y to 10YR to
7.5YR to 5 YR to 10R).
Value - The relative darkness or lightness
• from 1 (dark) to 8 (light). The value is often
a function of the amount of humic organic
material in the soil. Darker soils have more
organic material. Very black horizons may
be buried charcoal or accumulations of
MnO2
.

Whiter horizons may be the result of leaching as in an E

horizon, or the accumulation of carbonate or gypsum.
Chroma - The strength or intensity
the color from 0 (least with none of the hue) to 8 (most
vivid). This is indicative of the amount pigmenting
material present, but it is strongly influenced by the
texture of the soil.
• Example: a soil with color 10YR5/6 is 10YR hue, 5
value, and 6 chroma,
Interpreting soil color variations
⮚A- horizon is usually darker than B horizon
due to OM
⮚Dry soils generally have lighter color than
moist soil
⮚Bright colors throughout the profile indicates
well drainage
⮚Gray, bluish green denotes anaerobic
condition
⮚Red soils are typical of tropical and
subtropical areas while dark gray and brown
are typical of temperate regions
Effect of Soil Colors on other
Soil Condition
Soil color gives information about organic matter in the soil,
drainage, biotic activity, and fertility.

Dark (dark moderately dark light (pale

Condition grey, (brown to yellow brown, yellow)
brown to brown)
black)
organic high medium low
matter
erosion high medium low
factor
aeration high medium low

Available high medium low

nitrogen
fertility high medium low
 Cont....
Condition Subsurface soil
color
water-logged soils, dull grey (if in low rainfall
poor aeration soils 0-20 in.)

well drained soils yellow, red-brown, black

(if in forest soils)

somewhat poorly mottled grey (if in humid

drained soils soils)
www.adbio.com/science/soil/color.htm - 12k - Naka-cache.htm - 12k - Naka-cache -
Review Question
• Some soils exhibit mottles
A

because of
a) Lack of water
b) poor drainage
c) Low organic matter
d) hot temperature
o
Determination of the
soil Color
– Soil colors are also described
more technically by using Munsell
soil color charts,
– which separate color into components of
– hue (relation to red, yellow and blue),
– value (lightness or darkness) and
– chroma (paleness or strength).
–Approximately 322 color chips
are permanently mounted on 9
charts for basic collection of 7
hues (10R-5Y) and 2 gley
charts with apertures between
chips to make comparisons
easier.
❑ High Chroma colors are Glossy Finish.
❑ Can be used for evaluation of skin, hair and
eye color in anthropology, criminology,
pathology and forensic medicine.
❑ Loose leaf binder. Furnished with color-name
diagrams, instructions, and masks.
❑ 2000 Revised Washable Edition. Chart size: 4-
1/4" x 7-1/4". Chip size: 1/2" x 5/8".
Munsell Notation

• The Munsell code below each color in the

GLOBE color chart is a universal notation
that describes the soils' color.
Munsell Notation
The Munsell code below each color in the GLOBE color chart is a universal
notation that describes the soils' color.
1. Take a ped of soil from each horizon
and note on the data sheet whether it is
moist, dry or wet. If it is dry, moisten it
slightly with water from your water
bottle.
 • 3. Stand with the sun over
your shoulder so that
sunlight shines on the
2. Break the ped color chart and the soil
sample you are
examining.
Note: Sometimes, a soil sample may have more than one
color. Record a maximum of two colors if necessary, and
indicate (1) the Main (dominant color) and (2) the Other (sub-
dominant color).
Review Question
•L Describes the darkness or lightness of
soil color
a) Hue
b) Value
c) Chroma
d) intensity
Review Question:
N
Describes the strength of color
a) Hue
b) Value
c) Chroma
d) intensity
 Review Question

A The color of the soil is red which of the following

statement is correct
a)The soil contains high amount of organic
matter
b) The soil contains high amount of iron
c) The soil contains high amount of manganese
d) The soil has CEC content.
 Review Question
R
Soil high in manganese exhibit a
soil color of
a) brown
b) black
c) red
d) gray
L
Thank you!

KEY=CANR