Soils around the world vary in color, texture, structure, and chemical, physical, and biological composition. To the uninformed, soils may appear to be quite uniform, especially at the local level, but in reality they can be very different just a few feet away. Soils are a function of the five soil-forming factors: climate, organisms, relief, parent material, and time. Each of these factors range on a continuum, so the different soils of the world number in the thousands.
Soil scientists recognize 12 major orders of soils. A soil order classification is similar to the system biologists use to classify animals or plants into groups that have common properties. These orders are further refined into suborder, great groups, subgroups, families, and series. Thus, a name such as fine-loamy, mixed, mesic Typic Haplaquolls (Webster series) tells a soil scientist a great deal about the specific soil. Each state in the United States has an “official” state soil, just like each state has an official state flower or state bird. Be sure to check out the state soil in your location.
The entire section on soil orders is most appropriate for Grades 6+. It may be too much for younger grades. An exception would be to use the link below to find out what you state soil is. This is appropriate for any age group.
Lesson Objectives:
1) Describe the main characteristic of each of the soil orders.
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Alfisols - moderately leached soils often found in temperate forests
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Andisols - soils formed in volcanic ash
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Aridisols – desert soils
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Entisols - soils with little or no morphological (horizon) development
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Gelisols - soils with permafrost
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Histosols - organic soils
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Inceptisols - weakly developed soils
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Mollisols - grassland soils
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Spodosols – acidic, sandy forest soils under conifers
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Oxisols - very weathered soils of tropical and subtropical environments
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Ultisols – acidic, strongly leached, older soils
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Vertisols - clayey soils that swell when wet
2) Indicate where each order can be found (in general terms).
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Alfisols - temperate forests - generally east of the Mississippi
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Andisols - soils formed in volcanic ash – Pacific Northwest
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Aridisols – desert soils – desert southwest
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Entisols - soils with little or no morphological (horizon) development – Beaches, sand dunes, and floodplains
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Gelisols - soils with permafrost – tundra, Alaska
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Histosols - organic soils – very wet area, parts of FL, MN, AK, MI, ME, NC
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Inceptisols - weakly developed soils – almost anywhere
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Mollisols - grassland soils – the Great Plains
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Spodosols – acidic, sandy forest soils under conifers – Sandy areas of the North east to Minnesota, sandy areas of the Atlantic coastal plain
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Oxisols - very weathered soils of tropical and subtropical environments – Puerto Rico and Hawaii
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Ultisols – acidic, strongly leached, older soils – common in the Southeastern US
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Vertisols - clayey soils that swell when wet – parts of Texas west to the desert southwest and east through Alabama, Mississippi Delta Region, northern Great Plains and parts of California
3) List the order(s) found in your state
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soil orders found in the US to see its US exent.
Glossary of terms:
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See the soil orders above
Activities or information:
1) Soil Order Photos:
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Soil Taxonomy (all Grades) This is a PDF for a poster of all 12 orders plus individual PDFs for each order.
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State Soils Booklets - SSSA (All Grades) This has information and booklets for all of the state soils. Also includes an activity.
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World Soil Orders - (Grades 8+) This is a world view of where each soil order can be found.
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The Soil Orders in the United States - USDA-NRCS Clicking on each soil order will show more information and a map of that order’s distribution in the US. This is a great way to show where the order is found and the landscape, land use etc. connected with each.
Study Questions:
1) Using the web sites above find your state soil.
2) Using the web site above find what soil orders are present in your state.
