Agriculture Reference
In-Depth Information
T A B L E 9.3. Soil Orders According to U.S. Department of Agriculture (USDA)
Soil Order
Characteristics
Major Uses
Inceptisol
Soil that has little or no development
When topography is suitable, may be
used for crop production
Entisol
More developed than Inceptisol
although development is slight
When topography is suitable, may be
used from crop production
Alfisol
Light surface horizon with
well-developed horizons
Widely used for crop production
Mollisol
Deep dark surface horizon. Develops
under grass vegetation
Widely used for crop production
Aridisol
Soils that occur in arid regions
May be used for crop and animal pro-
duction if water is available
Vertisol
Soils with high activity clays that
develop wide (20 cm) and deep
(100 cm) cracks when dry
Can be farmed, although water infiltra-
tion and seedbed preparation are
difficult
Andisols
Soils containing material from volca-
noes. Often has high gravel content
and fast drainage
Can be used for agriculture if sufficient
water is available
Gelisols
Soils with frozen horizons
Generally not used for agriculture
Oxisols
Common in tropical climates have had
many components leached out of the
soil
Are commonly used for agricultural
production particularly pineapple
production
Ultisols
Ultimate in soil development have a full
complement of horizols
Are generally suitable of crop
production
Spodosols
Sandy soils developed under acid-
producing vegetation, has horizon of
deposited aluminum and organic
matter often with accompanying iron
Used for both tree and agricultural crops
Histosols
Organic soils
Are generally high productive and often
used for production of vegetable crops
addition different clays have different characteristics such as shrink - swell and their
cation exchange capacity that holds cation nutrients (elements with a positive
charge) in a form available to plants. Organic matter, air, and water also add their
own forms of complexity to soil. It is the complexity of soil that makes it particularly
suitable for plant growth, and understanding and managing this complexity can lead to
increased and improved food production.
In many cases it is not necessary to be able to identify a soil in terms of its official
name. Soils can be sandy, silty, or clayey. It is relatively simple to feel a soil's texture
by wetting it and working the wetted soil between thumb and forefinger (this is often
referred to as the feel method). A sandy soil will have a gritty, sandlike, feel. A silty
soil will have a flourlike feel, and a clay soil will be plastic, can form shapes it can
retain, and clays are usually sticky. Basically, sandy soils have high infiltration and per-
colation rates, that is, water moves through the soil easily. Silty soils will have slightly
lower infiltration and percolation rates and hold the most water for plant use. Clayey
soils will have low infiltration and percolation rates.
