Notes: Soil Formation and Composition
Soil Formation / Soil – The loose, weathered material on Earth’s surface in which plants can ______.How is soil formed?
Soil is formed as rock is broken down by ______and mixes with other materials on the surface.
Bedrock – The ______layer of rock beneath the soil. It gradually weathers into soil whenever it is exposed.
Soil Composition and Texture
/ Soil is a mixture of ______particles, minerals, decayed organic material, air, and water.
Humus – Dark colored the decayed organic material in ______; helps create ______in soil for air and water; rich in elements that plants need
Loam – soil made up of about equal ______of clay, sand, and silt; ideal for most plants
Soil Particle Size /
Soil Layers /
Soil Horizons / Soil horizon – layer of soil that ______in color and texture from layers above or below it.
Topsoil – Mixture of humus, ______and other minerals that forms the crumbly, topmost layer of soil; the ______horizon
Subsoil – The layers of soil beneath the ______that contains mostly clay and other minerals; the ______horizon
Soil / 1. Soil is a combination of ______and ______.
2. ______= decayed plant and animal material found in soil. Soil that contains 20-30% humus is considered a rich soil for plant growth.
Soil development /
Soil layers- The soil profile
/ ______or ______= the top layer of soil that contains more humus than the layers below.
______or ______= consists of clays and dissolved minerals that have been washed down from above. Contains less humus.
______= consists of weathered rock fragments, usually from the parent rock below.
______= the layer of rock beneath the soil. Frequently the parent rock of the soil above.
Georgia’ssoil / Southern Forest soil –form in ______and ______climate; low in humus.
Forming Humus / Litter – The loose layer of dead plant leaves and stems on the surface of ______.
Decomposers – Soil organisms that ______down the remains of dead plants and organisms and digest them.
Importance of Living organisms in Soil / Some soil organisms, like earthworms, ______the soil and make spaces in it for ______and water.
Other soil organisms make humus, which makes soil ______.
Soil Conservation / Soil is one of Earth’s most ______resources because everything that lives on the land depends directly or indirectly on soil.
Fertile soil is valuable because there is a ______supply.
Less than 1/8th of the land on Earth has soils well suited for farming.
Soil Damage and Loss / Soil can become exhausted, or ______its fertility.
Soil can also become lost to ______by water and wind.
- ______erosion can occur wherever soil is not protected by plant cover.
- ______erosion caused the Great Dust Bowl!!
The Dust Bowl – Loss of Topsoil / In the 1930s plowing removed the grass form the Great Plains and ______the soil. In times of drought, the topsoil quickly dried out, turned to dust, and blew away.
This event helped people appreciate the value of soil.
How to help in Soil Conservation? / Soil Conservation is the management of ______to prevent its destruction.
Three ways that soil can be conserved include contour plowing, conservation plowing, and crop rotation.
Contour Plowing
/ Contour plowing is the practice of ______fields along the contours of a slope.
This helps slow the ______of excess rainfall and prevents it from washing the soil away.
Conservation Plowing / Conservation Plowing disturbs the ______and its plant cover as little as possible.
Dead weeds and stalks of the previous year’s ______are left in the ground to help return soil nutrients.
Crop Rotation / Farmers ______different crops each year.
Different type of crops ______different types of nutrients from soil.