Soils One of Our Natural Resources SOIL Soil

Soils: One of Our Natural Resources!

SOIL Soil is made of loose, weathered rock and organic material.

The rock material in soil contains three parts: sand, clay, and silt.

Soil, on the average, consists of 45% mineral, 25% water, 25% air and 5% organic matter. This is just an average!

Important Terms • • • Humus is dark-colored organic matter made-up of decaying pieces of plants & animals. A horizon is a layer of soil. A soil profile is a cross-section of the different soil layers or horizons.

Soil Profile In a cross-section of soil, various zones are formed.

A Horizon: Topsoil This is generally the most productive layer of the soil. Conservation efforts are focused here!

A Horizon: Topsoil • Dark-colored • Topsoil • Most evolved-been around the longest • Contains the most humus • Where the organic matter is

A Horizon: Topsoil This layer is usually loose and crumbly with varying amounts of organic matter.

A Horizon: Topsoil • Leaching is the dissolving of minerals in water & carry down through soil horizons • Leaching occurs primarily in the A Horizon

B Horizon: Subsoils are usually lighter in color, dense and low in organic matter.

B HORIZON • Below the A Horizon • Light colored • Contains minerals leached from A horizon • Very few plant roots here

C Horizon: Transition This layer of transition is almost completely void of organic mater and is made up of partially weathered parent material.

C HORIZON – – – Below B horizon Bottom layer Least evolved No humus Solid rock below (bedrock)

Bedrock Below the C horizon the unweathered bedrock will be found.

There are thousands of different soils throughout the world. Five important factors influence the specific soil that develops.

5 Factors of Soil Development • Parent Material • Climate • Type of organic matter • Topography • Time the soil has been developing

Parent Material This refers to the minerals and organic materials present during the soil’s formation.

Parent Materials from volcanoes, sediment transported by wind, water, or glaciers are some examples.

Question Break!

Think about prairie soil. Where do you think the “parent material” came from?

Climate The climate of a particular region can have a major influence on the rate of soil formation.

Climate Weathering processes like the cycles of freezing and thawing (ice wedging), along with wetting and drying vary with each region.

Climate – The thickness of horizons depends upon climate – Soil horizons are thinner where there is little rainfall

Living Organisms Both plants and animals help create soil.

Living Organisms As they die, organic matter incorporates with weathered parent material and becomes part of the soil.

Question Break!

Can you think of some organisms that might help mix and enrich the soil?

Living Organisms The actions of moles, earthworms, bacteria, fungi, and insects mix and enrich the soil.

Topography The slope or hilliness of a region can have a major influence on the moisture and erosion of soils.

Topography In many regions, moist, poorly drained soils are located in low areas.

Topography Drier, well drained soils are often found in sloping hillsides. Erosion is often a problem here and can lead to lose of topsoil.

Time It takes hundreds of years to form one inch of soil from parent material. Under extremely poor conditions, it can take thousands of years.

Time Only the top few centimeters are productive in the sense of being able to sustain plant growth.

Time This is why soil conservation is so important!

Last Question!

What do you think leads to soil erosion?

Causes of Soil Loss • Caused by: – Overgrazing – Clearing of forests (rainforest) – Poor farming practices “Dust Bowl” happened because of poor farming practices

Ways to Conserve Soil • • Contour plowing Terraces Crop Rotation http: //en. wikipedia. org/wiki/Terracing_(agriculture) Terrace (agriculture) - Wikipedia, the free encyclopedia