These soils are some of the most fertile soils in the world! Most of the products that we use, touch, or eat everyday come from prairie soils. They are responsible for growing a majority of the foods that Americans eat. Each farmer in Kansas, a prairie soil state, can feed over 130 people. These are the breadbaskets of the world. They are located in the large, central parts of continents. These soils form where it is too dry for a forest, and too wet for a desert. Instead, long, tall grasses form. Soils are thick and deep, and have many nutrients because of the large amounts of grass roots that die.
This lesson is appropriate for grades 4+.
Prairie Soils - link for class presentation
Lesson Objectives:
1) What are the characteristics of prairie soils?
- Prairie soils are rich – have a good nutrient supply for growing plants
- Prairie soils are soft – grass roots create good soil structure in the topsoil
- Prairie soils are deep – the nutrient-rich topsoil is at least 25 cm (10 inches) thick
2) Which ClORPT factors are most important in prairie soil formation?
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*Climate – Prairie soils form in temperate (distinct seasons, e.g., winter, spring, summer, fall; or dry season and wet season), semi-arid to humid regions
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Organisms – *Grasses are the dominant vegetation in prairie soils, though other plants are present, including legumes (like prairie clover). Insects, earthworms, bacteria, and fungi decompose the dead roots and leaves, and mix the soil. Some birds, reptiles and rodents (like prairie dogs), live in the soil. Bison, deer, antelope and prairie dogs graze the grasses.
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Relief – Prairie soils typically form on level to moderately sloping (0 to 10%)
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Parent material – Prairie soils form in glacial deposits in Canada and the northern states, and in windblown sediments (eolian or loess) in the central Great Plains, and river and deposits throughout the region
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Time – Prairie soils are younger in the north (like Iowa and Minnesota that were covered by glaciers until about 10,000 to 15,000 years ago), and older in the south (like Texas)
3) How do prairie soil characteristics differ in soils with tall or short grasses?
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Color
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Darker colors mean more organic matter
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Red colors indicate oxidized iron
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Yellow colors generally indicate oxidized, hydrated iron
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Gray or blue colors generally indicate reduced iron or manganese, which is a characteristic of water-logged soils
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White may indicate the presence of carbonates, especially in the short-grass prairie soils
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Depth
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Soils forming under tall grasses are typically deeper
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Soils generally get deeper from west to east, as precipitation increases
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Organic matter
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Soils forming under tall grasses typically have more organic matter
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Organic matter generally increases from west to east as precipitation increases
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Organic matter generally increases
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Identify the importance of prairie soils
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Prairie soils are the “breadbaskets” of the world
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Most of the cereal grains (corn, wheat, rice, etc.) and pulses (soybeans, bean, peas, etc.) are produced on prairie soils
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Most of the beef, sheep, and goat production in North America occurs on prairie soils
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Glossary of Terms:
In Current Glossary:
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CLORPT – The five factors that influence what type of soil forms: Climate, organisms, relief (landscape), parent material, and time.
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Erode (erosion) – To wear away, or remove, rock or soil particles by water, wind, ice, and/or gravity.
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Groundwater – Water that collects underground in the pore spaces of soil and rock. An important source of drinking water.
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Horizon – A layer of soil with properties that differ from the layers above or below it.
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Organic matter – Material derived from the decay of plants and animals. Always contains compounds of carbon and hydrogen.
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Organisms – Living things such as bacteria, fungi, plants, and animals.
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Parent material – The source from which a soil formed. Can be bedrock or materials carried and deposited by wind, water, glaciers, and/or gravity. May also be the C horizon in a soil profile.
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Productive – A term used to describe a soil that has the capacity to grow an abundance of crops.
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Relief – The shape of the land surface created by features such as hills and valleys.
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Runoff – Water from precipitation or irrigation that does not soak into the soil, but flows off the land and reaches streams and rivers.
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Sediment – Any particle of soil or rock that has been deposited by water, wind, glaciers, or gravity
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Slope – A landscape, or surface, that is tilted or inclined.
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Topsoil (A horizon) - Mostly weathered minerals from parent material with a little organic matter added. The soil that formed on the land surface.
Other glossary words:
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Eolian – Parent materials deposited by wind with more than 5% sand
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Prairie – Grasslands that form in climates too dry to be a forest and too moist to be a desert.
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Loess – Parent materials deposited by wind with less than 5% sand
Activities or Information:
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Compare/contrast the (book) photos of the Mollisols from tall and short grass prairies
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Use the state soils monoliths to compare characteristics of Mollisols from
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Features to examine
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Depth to color change
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Sometimes structure is discernible in photos (look like clods or cracks
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What is the difference in mean annual temperature and precipitation for each state?
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Bring food items or canned goods, clothing, soft drinks, etc., to the classroom and trace each item back to the soil. Most of these products can be traced to items produced on prairie soils. (See “Hungry, Naked, Homeless, and Breathless”. Trees are not produced on prairie soils.)
Test Questions:
1) Why are prairie soils so important to humans?
2) How do soils differ between short and long grass prairies?
3) What do darker colored soils mean?
4)What are the main characteristics of prairie soils?
