There’s a few different ways to classify/categorize soils.
In this guide, we outline how each soil can be classified in these different ways, and give a description of each soil type as well.
We also look at where the different types of soil might be found in the world.
Summary – The Different Ways To Classify Soil Types
Different Main Ways To Categorize Soils
By soil order (soil taxonomy by soil order is considered by some to be the highest level of classifying soils)
By soil traits and characteristics (particle size is the main trait that can group soils, but texture and structure might be others)
By color
By biome
By region or zone
Miscellaneous soil types
Subcategories Of Soil
The reality is that there are thousands of different types of soils, even beyond the categorisations above, that can be broken down into the main groups, sub groups, great groups, families, series’ and so on.
They all vary in color, texture, structure, and chemical, physical, and biological composition.
Why There Are Different Soils
Just as one example, soils with different types of parent rock material beneath them will inherit different base minerals from this parent rock (the soil taxonomy wikipedia.org resource does a good job of describing this for soil orders like Mollisols and Vertisols)
Where Soils Are Found Worldwide, & Why They Differ Between Regions
Soils differ between countries around the world, but also in the different regions within countries
The reasons for this is what we outlined above – parent rock material (that soils get their minerals and other traits and properties from), climate, and other variables differ from location to location.
Some soils are predominantly found in one or a small number of locations throughout the world, whilst some are found in many locations.
In the guide below we outline what soils might be found in different regions
Number Of Soils Types In Different Countries
The US has 12 different types of soil orders, and each State has a different representative soil
There’s over 1, 800 British soils
India might have 8 main soils, plus and ‘Other Soils’ category
Australia might have 6 main types of soil, and each State has it’s own representative soil
So, each country has different soils spread across each region of the country
In the guide below we discuss the different types of soils found in the US, Australia, India and the UK
Determining Soil Types In An Area
Apart from looking at soil maps to see what soil you might have in your area, soil tests can be done to further assess the type of soil on a plot of land.
Soil Orders (& Sub Orders)
According to uidaho.edu, the highest level of classification for soils are soil orders.
Wikipedia.org mentions that the hierarchy is – Order, Suborder, Great Group, Subgroup, Family, and Series
The different soil orders each have distinct characteristics and ecological significance, and according to wikipedia.org, those properties are ‘depth, moisture, temperature, texture, structure, cation exchange capacity, base saturation, clay mineralogy, organic matter content and salt content’
Each soil also takes up a different % of land worldwide across all countries
There are 12 different soil orders.
Entisols and Inceptisols take up the most global land as a %.
The different soil orders are:
– Alfisols
These soils make up 10% of global ice free land.
They are similar to Ultisols, but less intensively weathered and less acidic, and more fertile.
These soils are clay based (have an accumulation of clay), have relatively high native fertility, and are very productive soils.
They tend to have a high aluminum and also iron content.
They support about 17 percent of the world’s population.
– Andisols
Make up 1% of global ice free land.
A black soil that is formed from the weathering of volcanic materials such as ash
They have capacity to hold a lot of water, are very fertile, are good for crops (and also forests), but can fix phosphorus (and wikipedia.org mentions that this can impact fertility)
– Aridisols
These soils make up 13% of global ice free land
They are dry soils, found in dry or arid climates, such as deserts.
They are generally used for range, wildlife and recreation, and sometimes agriculture, but only if irrigation is available.
– Entisols
These soils make up 16% of global ice free land, and are the largest soil type of all.
They show little to now soil development, are made of weathered/eroded rock or sediment type soils, and have great diversity.
Soil degradation/erosion tends to be quicker than soil formation in places where Entisols are found.
They are found in steep, rocky settings, but can also be found in river valleys and associated shore deposits that provide cropland and habitat for millions of people worldwide.
– Gelisols
These soils make up 9% of global ice free land.
They are found in (often extreme) cold climates, and are either permanently frozen, or have permafrost within 2m of the soil surface.
They usually have little agricultural value even when thawed out.
– Histosols
These soils make up 1% of global ice free land.
Many form in wetlands (these soils are referred to as peats, mucks and boglands), can be underwater, and contain up to around 20 to 30% organic matter.
They can act like a sponge, tend not to drain well (or have problems when drained), and can be acidic.
– Inceptisols
These soils make up 10% to 15% of global ice free land.
They show little to moderate soil development, but are more developed than Entisols.
They are often made of degraded rock material
A certain % are found in mountainous regions and are used for forestry, recreation and watershed.
Inceptisols support approximately 20 percent of the world’s population, the largest percentage of any of the soil orders (uidaho.edu)
– Mollisols
These soils make up about 7% of global ice free land (but in the US they are the most extensive soil order, accounting for approximately 21.5 percent of the land area)
They are thick, dark/black soils, with a high organic content (that comes from the roots of prairie plants), and are some of the most fertile and important and productive agricultural soils in the world.
They are usually found in prairie and grassland ecosystems. Some are also found in hardwood forests.
Wikipedia.org has a good description of their base, and how they form.
– Oxisols
These soils make up 7.5% of global ice free land.
They are highly weathered soils and have extremely low native fertility. They can have a high iron content.
They can however be quite productive with inputs of lime and fertilizers.
They are found in tropical and subtropical environments.
– Spodosols
These soils make up 2.5% of global ice free land.
They are usually sandy soils (high sand content), that are acidic, and have low fertility and low clay content.
They can support forests, and with the addition of lime, sometimes agriculture.
– Ultisols
These soils make up 8.5% of global ice free land.
They tend to form in humid areas and are intensely weathered.
The also tend to be acidic soils, with accumulated clay.
They support forests, and can be successful (and very productive) in agriculture if fertilizer and lime is added.
They support 18 percent of the world’s population
– Vertisols
These soils make up 2.5% of global ice free land.
They are highly fertile clay rich soils, that expand and shrink, and can develop deep cracks, depending on factors like moisture content, and how dry or wet the weather is at the time.
Because of the high clay content, they can present engineering problems.
Can support agriculture when irrigation is available for a range of crops, although pooling of water on these soils can be an issue.
Read in more depth about the different soil orders at:
The Twelve Soil Orders (uidaho.edu) (this resource also has graphics that show where the soil orders are predominantly found geographically, including worldwide and in the US, as well as photos of what each soil order looks in terms of their cross section, appearance and different layers)
Global Soil Regions – The 12 Types Of Soil, Defined by the USDA (adama.com)
Soil Orders Simplified (soilsmatter.wordpress.com)
USDA Soil Taxonomy, Soil Orders (wikipedia.org)
Types Of Soils In The US (gardenguides.com)
The above soil orders also have suborders, each of which are listed at globalrangelands.org
Soil Types By Characteristics & Traits
Soil traits and characteristics includes texture, particle size and other features.
Soil characteristics can also be categorized into chemical, physical, and biological characteristics
One of the main ways to classify soil types is by particle size (and sometimes the balance of these particles in a soil type too).
Examples of soils grouped by traits and characteristics like particle size include:
– Sandy Soil
A light soil with large particle size.
Because it has poor water retention and low nutrients, it’s not seen as a soil that is naturally good for plant life.
Read more about sandy soils in this guide
– Clayey Soil
A heavy soil that is very good at water retention/holding water.
Although can be a soil that’s rich in organic matter, it’s not good for growing lot of plants.
Read more about clayey soils in this guide
– Silty Soil
Has medium particle size.
Is a light soil that holds water well.
It’s fairly fertile, although some say it doesn’t hold nutrients as well as some other soils, and benefits from the addition of organic matter.
Read more about silty soils in this guide
– Peat Soil
Usually dark brown or black in color, high in organic matter (and low in nutrients), and holds water well – all qualities that make it good for a range of plants.
Is usually an acidic soil or a soil that contains acidic water.
Peat soil is commonly imported into gardens to provide a planting base.
Read more about peat soil in this guide.
– Chalky Soil
Can be a light or heavy soil, but is an alkaline soil because of the lime or calcium carbonate found in it.
Doesn’t suit the growth of plants that need acidic or regular conditions to grow.
Mineral can leach out of chalky soil quickly.
Read more about chalky soil in this guide.
– Loam Soil
One of the best and most fertile soils for cultivation of plants and crops of many kinds – referred to as the ideal soil type.
Consists of sand, clay, and silt – so it combines the best qualities of each.
Has good aeration, but holds water well and also drains it well.
Can benefit from topping up with organic matter.
Read more about loam soils in this guide
Some say the best soil is a loam type soil that is 40 percent sand, 40 percent silt, and 20 percent clay as it’s fertile, but also has good water drainage, good moisture retention and allows good infiltration of air and water (dummies.com).
– Other Information Of Soils By Characteristics & Traits
Read more on soil types by texture, traits and characteristics at the boughton.co.uk, toppr.com, agverra.com, dummies.com (mention how soils can have different balances of different particles like sand, clay etc.), gardenersworld.com and resources listed burkesbackyard.com.au
You can also classify soil by pH:
Read more about acidic soils in this guide
Read more about alkaline soils in this guide
Soil Colors
Soils can be categorised by their color in many countries across the world.
Different colored soils might have different traits and properties.
One such example is in India …
– Red Soil, & Yellow Soil
Found in India.
Red soil gets its colour from the iron found in its composition in a crystallized form.
The soil takes on a yellow colour when it is hydrated.
These soils are generally found in the Western Ghats, Odisha and Chattisgarh.
– Black Soil
These soil are rich in lime, iron and magnesia.
They are mainly found in the Deccan Plateau in Maharashtra, Madhya Pradesh, Gujarat etc.
Read more about them at the toppr.com and researchgate.net resources
Note that there are many other examples of soils being classified by color in countries other than India.
Soil Biomes
It’s not really a way to classify soils specifically, but it’s a way to classify where soils might be found according to biome.
From soils4teachers.org:
There’s 10 major soil biomes worldwide with different characteristics
[Some of the different soil biomes are] urban, desert, tundra, prairie, tropical (savanna and forest), temperate/boreal, alpine, wetland and volcanic soils.
[You can look at a world map of the different biomes at the soils4teachers.org guide]
Some soil orders match up with different biomes.
You can also see a general map of the different soil biomes and soil orders around the world on one big map at soils4teachers.org
Soil Regions Or Zones
Sometimes soils are categorised according to the zone or region they are found in.
The zone could be categorized by a type of landscape or climatic condition.
A few different examples in different countries include …
– Australia
Soils Of The Alpine & Perhumid Zones
Soils Of The Humid Zones
Soils Of The Seasonably Humid Zones
Soils Of The Semi Arid Zones
Soils Of The Arid Zones
Read more about them at the abs.gov.au resource
India
Mountain Soil
Arid Soil
Read more about them at the toppr and researchgate.net resources
Representative Soils Of Different Regions Within A Country
As one example, the US has a representative soil for each of the 50 states (you can read more about them at the nrcs.usda.gov resource)
A representative soil is the soil that is dominant, or representative of a State or province within a country
A representative soil doesn’t make up 100% of soil in that state – soil can differ across different locations in a State, or even across different parts of a private plot of land.
Each representative soil has different factors that contribute to it’s formation, and has different traits which make it suitable for different uses compared to other representative soils.
The resource listed below about country specific soils outline things such as what the type of soil is that is found in a particular state, what that soil can be used for, what the soil might be good for, what limitations the soil might have, how the soil might be managed, and more
Soils In The United States
There is a variety of mineral and organic soils across the 50 states in the United States
This a result of the diversity of geologic materials, geomorphic processes, climatic conditions, biotic assemblages and land surface ages in the United States
Most of the mineral soils contain significant quantities of organic matter, but not enough to qualify for classification as organic soils
Representative Soils In The US
Two places you can go to find out more about the soil that is representative of a particular state in the US are:
US State Soils (soils4teachers.org)
US State Soils (nrcs.usda.gov)
If we take Alabama for example, ‘Bama’ soil is:
… well suited to many uses including crop production, pasture for hay or animal grazing, forest, and most urban uses.
Cotton, corn, soybean, and peanuts are the main cultivated crops …
– soils4teachers.org
Using the above Alabama state example, Bama soil isn’t found throughout the entire state:
The Bama soil is present in nearly 40% of Alabama counties
– soils4teachers.org
Soil Orders In The US
Overall, there’s 12 different types of soil orders in the US, each with different characteristics.
Specific Examples Of Soils In The US
The bbc.com resource listed specifically explains more about the fertility of the black loam soil in Iowa, and how it’s been used for different crops in agriculture
Soils In The UK
In terms of soils in the UK:
… there are over 1,800 British soils with a range of different profile types, despite the modest land area and limited range of cool, temperate climates (soils.org.uk)
You can view a map of the basic soil types across Britain here, such as chalk and limestone, heavy, medium, peaty, sandy and light.
The UK Soils Observatory also has a soilscape map you can check out on their website.
Soils In India
According to toppr.com, and researchgate.net, soils in India can be broken down into:
Alluvial Soil
Black Soil
Yellow Soil, and Red Soil
Laterite Soil
Arid Soil
Saline Soil
Peaty Soil
Mountain Soil
Other Soils
A more in depth breakdown of Indian soils, what locations they are found in, and what can be grown in them can be read at:
Major soil types in India (toppr.com)
Different soils and the crops they might be suitable for in India (researchgate.net)
Soils In Australia
Representative Soils In Australia
You can find out more about the soil that is representative of a particular state in Australia at soilscienceaustralia.org.au
They list the soils representative of each State (and Territory) as:
New South Wales – Red Chromosol
Northern Territory – Kandasol
Queensland – Vertosol
South Australia – Calcarosol
Tasmania – Ferrosol
Victoria – Mottled Brown Sodosol
Western Australia – Yellow Chromosol
If we take South Australia as an example of what soil is predominantly found in this State:
The South Australian Branch selected a Calcarosol as the State soil.
Calcarosols are calcareous sandy loams that are well drained, alkaline, moderately fertile and reasonably deep.
They occur throughout SA and are used widely for cereal growing, pasture and irrigated horticulture, particularly vineyards.
– soilscienceaustralia.org.au
Another example is Victoria:
The Victorian branch selected the Mottled Brown Sodosol as their State Soil.
Also known as Yellow or Brown Duplex soils, Mottled Brown Sodosols are widespread across Victoria, predominantly in the 450 – 800 mm rainfall zone.
They are used mainly for dairying and grazing, but increasingly land use is changing to cropping in the south-west.
– soilscienceaustralia.org.au
Using the above Victoria state soil example of how soils differ within a State:
Mottled Brown Sodosols are widespread across Victoria, predominantly in the 450 – 800 mm rainfall zone [so, they are widespread but not necessarily found absolutely everywhere]
– soilscienceaustralia.org.au
Different Types Of Soils In Australia
Abs.gov.au has some further information on the different types of Australian soil:
Stony and Shallow Soils
Soils Of The Alpine & Perhumid Zones
Soils Of The Humid Zones
Soils Of The Seasonably Humid Zones
Soils Of The Semi Arid Zones
Soils Of The Arid Zones
– abs.gov.au
Soil Quality Across Australia
In terms of soil quality across Australia – the soil quality in each state can also be examined at soilquality.org.au
Miscellaneous Soils, Or Other Soils
Soils can be classified in other specific or custom ways according to defining characteristics or features.
Just one example might include saline or alkaline soils.
But, there can be many more.
Sources
1. https://www.adama.com/documents/130172/4752576/Infographic+Type+Of+Soils
2. https://www.soils4teachers.org/around-the-world
3. https://soilsmatter.wordpress.com/2015/01/05/the-soil-orders-simplified/
4. https://www.soils.org/discover-soils/soil-basics/soil-types
5. https://www.boughton.co.uk/products/topsoils/soil-types/
6. https://www.toppr.com/guides/science/soil/types-of-soil-and-suitable-crops/
7. https://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/edu/?cid=stelprdb1236841 (state soils in the US)
8. https://www.gardenguides.com/107420-types-soil-us.html
9. http://agverra.com/blog/soil-types/
10. https://www.dummies.com/home-garden/gardening/urban-farming-how-to-determine-your-soil-type/
11. https://www.gardenersworld.com/plants/find-out-your-soil-type/
12. https://www.burkesbackyard.com.au/fact-sheets/in-the-garden/gardening-tips-books-techniques-and-tools/soil-type-test/
13. https://en.wikipedia.org/wiki/Soil_type
14. https://en.wikipedia.org/wiki/Soil_classification
15. – https://www.bettermeetsreality.com/the-different-soils-worldwide-in-different-countries-different-climates/
16. https://www.toppr.com/guides/general-knowledge/resources-of-india-and-world/soils-of-india-and-the-world/
17. https://www.researchgate.net/post/How_to_determine_the_kinds_of_crops_suitable_to_different_types_of_soil
18. http://www.abs.gov.au/ausstats/[email protected]/Previousproducts/1301.0Feature%20Article801966
19. https://globalrangelands.org/topics/rangeland-ecology/twelve-soil-orders
20. https://www.uidaho.edu/cals/soil-orders
21. https://en.wikipedia.org/wiki/Soil_in_the_United_States
22. http://www.soil-net.com/dev/page.cfm?pageid=secondary_intro_differences&loginas=anon_secondary
23. https://www.soils.org.uk/soils-britain
24. https://www.soils4teachers.org/state-soils
25. https://www.soilscienceaustralia.org.au/about/about-soil/state-soil
26. http://www.soilquality.org.au/
27. https://www.soilscienceaustralia.org.au/branches/south-australia/
28. https://www.soilscienceaustralia.org.au/branches/victoria/
29. https://en.wikipedia.org/wiki/USDA_soil_taxonomy
30. https://www.soils.org/about-soils/basics/types/
31. https://www.bbc.com/future/bespoke/follow-the-food/why-soil-is-disappearing-from-farms/
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