SOIL SCIENCE
SOIL COLOUR
Dr. Madhurima Banik
Assistant Professor (Soil Science)
The Neotia University
SOIL COLOUR
•Soil colour indicates many soil features.
•A change in soil colour from the adjacent soils indicates a difference in the
soil`s mineral origin (parent material) or in the soil development.
•Soil colour is inherited from its parent material and that is referred to as
lithochromic, e.g. red soils developed from red sandstone.
SOIL COLOUR
• Soil color: is one property that can be used to describe horizonation and soil
morphology.
• The soil color does not effect the behavior of the soils, but provides insights into
environmental conditions, formation processes, and other influences on the soil.
• Used is used in classifying soils.
Composition of soil
SOIL COLOUR
• Soil color: does not affect the behavior and use of soil; however, it can indicate the
composition of the soil and give clues to the conditions that the soil is subjected to.
• Soil can exhibit a wide range of colour; gray, black, white, reds, browns, yellows and
under the right conditions green.
Classification of Soil colour
• Soil colour is usually due to 3 main pigments:
• Black—from organic matter
• Red—from iron and aluminium oxides
• White—from silicates and salt.
• Colour can be a useful indicator of some of the general properties of a soil, as
well as some of the chemical processes that are occurring beneath the surface.
SOIL COLOUR
CAUSES OF SOIL COLOUR
Soil color is influenced by the amount of minerals present in the soil.
• Yellow or red soil indicates the presence of iron oxides.
• Dark brown or black colour in soil indicates that the soil has a high organic matter
content.
• Wet soil will appear darker than dry soil.
• The presence of water also affects soil color by affecting the oxidation rate. Soil that
has a high water content will have less air in the soil, specifically less oxygen.
• In well drained (and therefore oxygen rich soils) red and brown colours caused by
oxidation are more common, as opposed to in wet (low oxygen) soils where the soil
usually appears grey.
Determination of soil colour
• The soil colours are best determined by the comparison with the Munsell colour.
• This colour chart is commonly used for this purpose. The colour of the soil is a result
of the light reflected from the soil.
• soil colour rotation is divided into three parts:
Determination of soil colour
• Hue - it denotes the dominant spectral colour (red,yellow ,blue and green).
• Value - it denotes the lightness or darkness of a colour (the amount of reflected
• light).
• Chroma - it represents the purity of the colour (strength of the colour).
• The Munsell colour notations are systematic numerical and letter designations of
each of these three variables (Hue,Value and Chroma).For example ,the numerical
notation 2.5 YR 5/6 suggests a hue of 2.5 YR,value of 5 and chroma of 6. The
equivalent or parallel soil colour name for this Munsell notation is `red`.
MUNSELL SOIL COLOUR CHART
Factors affecting soil colour
There are various factors or soil constituents that influence the soil colour which
are as follows:
• Organic matter: soils containing high amount of organic matter show the
colour variation from black to dark brown.
• Iron compounds: soil containing higher amount of iron compounds generally
impart red, brown and yellow tinge colour.
• Silica, lime and other salts: Sometimes soils contain either large amounts of
silica and lime or both.
