The document discusses soil classification systems including the US Soil Taxonomy system which categorizes soils into Orders, Suborders, Great Groups, and other levels based on distinguishing characteristics. It also describes the major soil types found in Pakistan which are classified regionally as Indus basin soils, Bongar soils, and others. The classification of soils provides important information about their properties and development.

2. SOIL CLASSIFICATION
AGRICULTURE RESEARACH
INSTITITUTE (ARI)TANDOJAM

3. MASHOOQ HUSSAIN ODHANO
ASSISTANT RESEARACH OFFICER
AGRICULTURE CHEMISTRY (SOILS) SECTION
AGRICUTLURE RESEARCH INSTITUTE
TANDOJAM

4. Important Facts to Know
• Know the classification scheme of the US
System of Soil Taxonomy
• Understand the value of learning key
components of the soil taxonomy system.
• Be able to identify the distinguishing
characteristics of each soil Order, and
under what conditions each may be expected
to exist.

5. What is soil classification? Give old
classification of soil.
 Soil classification is dynamic in nature and
keeps on changing and adjusting as
knowledge and understanding of the soil
increase.

6. Geological Approach divided into
two groups:
 Sedentary
 Transported
 The classification was further improved and
soils were groups into red soils, black soils
(regurs),laterite and lateritic soils, delta
soils, desert and tarai soils.

7. Soil
 The upper layer of the earth which is
composed of different thin rock particles
is helpful in the growth of vegetation
and plants that is called soil.

8. Soil profile:
a vertical
section of soil
from the
ground surface
to the parent
rock.

10. Basic Components of Soil
Soil has three basic components.
 1. Solid particles like salt, mineral and organic
matter.
 2. Air.
 3. Water

11. Classification of Soils
 The soil of Pakistan may be classified according to the regional basis.
 Indus basin Soils
 About 60% of Pakistan's total land area is classified as unusable for
forestry or agriculture because it consists of deserts and mountains.
Pakistan’s soils are mostly dry and have high concentrations of
calcium carbonate and a low content of organic matter. The major soil
groupings are Indus basin soils, mountain soils, and sandy desert
soils.
74.3% of Pakistan’s soils are composed of these six types of soil:
1. 30.6% Mountain/Valley: Patchy soils that are a loamy-gravelly mix
2. 14.7% Rolling/hilly sandy soils
3. 11.4% Loamy-clayey soils
4. 6.6% Rock out-crop and loamy soils, very shallow
5. 5.8% Mainly loamy to partly gravelly soils
6. 5.2% Loamy soils

12. It is also true that Pakistan’s soil can be classified
regionally, or according to where it is found in the county.
From that perspective, there are also six soil types:
1. Indus basin soils: The soils found along the current
course of the Indus River are due to alluvial deposits made
by that river depositing sediments every spring.
2. Bongar Soils: These soils are found in the historic Indus
plain and are the best soils for agriculture in the country.
Usually they’re far from the present-day bed of the Indus
River.
3. Khaddar Soils: Also found along Pakistan’s rivers is this
soil. It formed when, every year during flood, a new layer of
salty clay was deposited.
4. Indus Delta Soils: These soils cover the current Indus
River delta. Most of this soil is very clayey and was
developed under seasonal floodwaters.
5. Mountain Soils: These rocky soils mostly cover the
highlands of northern and western areas of Pakistan.
6. Sandy Desert Soils: These soils are made by the
deposition of sand, layer by layer, year after year, for
thousands of years. They’re found in the arid and semi-arid
areas of Pakistan.

13. The general principles of natural soil
classification systems are:
 A natural system of classification should express general
or universal relationships that exist in nature. One should
be able to understand, remember, generalize, or predict
from information obtained.
 The scheme should be based on characteristics or attributes
of things classified as related to their genesis. It should
place similar things together on the basis of their
properties.
 It is technically impossible to use all of the properties of
soils to classify them. Judgment based on existing
knowledge must be used to determine which properties are
most important.


14. The US System of Soil Taxonomy
The US System classification scheme contains 6
categories:
1. Order – the most general grouping
2. Suborder - defined by moisture, temp,
dominating chemical or textural
features
3. Great Group - by differentiating horizons
4. Subgroup - three types: typical (typic),
intergrade, not one of the other two
5. Family - plant growth or engineering
properties.
6. Series – common name, like yours and
mine.

15. In addition to these categories, we have the soil
Phase (or soil Type), which refers to surface
properties such as texture, thickness, slope,
coarse fragments, salinity, erosion, etc.
This is added to a series name (like Aiken clay
loam, eroded phase).
Order, Sub-Order, Great Group, Sub-Group,
Family, Series and Phase or Type

16. SOIL ORDERS (12 major units of classification
according to the US 10th Approximation)
Alfisols: Relatively high base saturation; not
organic rich; evidence of clay transport.
Andisols: Soils derived major properties from
volcanic parent material. High P fixation.
Aridisols: Arid soils; Low in organic matter; high
in salts and pH.
Entisols: Leftovers; Not well-developed even
after long periods (can occur anywhere)

17. Gelisols: permafrost.
Histosols: Soils formed from organic matter
(peats and mucks).
Inceptisols: Still forming; Water is available for
soil formation (e.g., glaciated soils).
Mollisols: Brown-black surface horizons; High in
organic matter, vermiculite or smectite clays;
Base saturation usually > 50% (e.g., Iowa farm
soils) Most extensive in the US (25%).

18. Oxisols: Highly-weathered; Only quartz, kaolinite, and Fe
and Al oxides left (e.g., tropical rainforest).
Spodosols: Evidence of Fe, Al, and organic matter
transport; Often a whitish E Horizon (e.g., boreal forest).
Ultisols: Clay transport like Alfisols, but much more
acidic. Higher temperature; Often highly weathered (e.g.,
Southeastern U.S.).
Vertisols: Mixed soils; Swelling clays, frost, etc cause
lower horizons to mix with upper horizons; Often
characterized by cracks.

19. Photo of soil profile
Aridisol Entisol
Photos courtesy of USDA NRCS, National Survey Center
http://www.statlab.iastate.edu/soils/photogal/orders/soiord.htm

20. Photo of soil profile
Gelisol Histosol
Photos courtesy of USDA NRCS, National Survey Center
http://www.statlab.iastate.edu/soils/photogal/orders/soiord.htm

21. Photo of soil profile
Inceptisol Mollisol
Photos courtesy of USDA NRCS, National Survey Center
http://www.statlab.iastate.edu/soils/photogal/orders/soiord.htm

22. Photo of soil profile
Oxisol Spodosol
Photos courtesy of USDA NRCS, National Survey Center
http://www.statlab.iastate.edu/soils/photogal/orders/soiord.htm

27. •Five of these orders exist in a wide variety of
climates: Entisols, Inceptisols, Histosols, Andisols,
and Vertisols.
•The others are primarily a product of time.
•Worldwide extent:
Aridisols 19%
Alfisols 13%
Inceptisols 9%
Mollisols 8%
Oxisols 8%
Others 43%
One-fifth of world’s surface is mountainous and not
classified.

28. Sub-Orders
Sub-Orders are differentiated on the basis of
additional soil properties and horizons that are
related to soil moisture, temperature, and/or
dominating effects of chemical or textural
features.
Sub-Orders are distinctive within a given Order
and are not interchangeable. For example:
Histels Fibrists Psamments Xerepts Ustands
Argids
Cryolls Torrerts Aqualfs Orthods Humults
Torroxs
See sections: 7:7 through 7:18

29. Great Group
Soil Great Groups are sub-divisions of the Sub-
Orders and have been established largely on the
basis of differentiating soil horizons and other
prominent soil features.
The Great Group level of taxonomy consists of the
combination of 3 descriptive roots.
For example:
Argi-xer-olls – Argixerolls
Calci-torr-erts – Calcitorrerts
Hal-aqu-epts -- Halaquepts

31. Sub-Group and Family
There are 3 levels of Sub-Groups; the central (typic)
concept, intergrades, and extragrades.
Family groupings are based on:
1) particle size class,
2) minerals,
3) temperature,
4) rooting depth,
5) maybe others like pH, lime, cracking, particle
coatings, etc.

33. Examples of soil classifications and what they
mean:
Waca series (Truckee, CA):
Classification: loamy-skeletal, mixed, frigid,
Andic Xerochrepts
Translation: loamy soil texture with >35%
coarse fragments, mixed mineralogy, mean
annual temperature <8oC, dry in summer, dry
soil with Andic properties but not qualifying as
an Andisol, not fully formed with light colored
low organic matter A horizon.

34. Corbett series:
Classification: Typic Frigid Xeropsamments
Translation: Typical of classification, mean
annual temperature <8oC, dry in summer, sandy
textured soil with minimal profile development.