Soil Science Review

Vocabulary Conserve- to save or use as little as possible Erosion- the moving of soil form one place to another Sand- large grains of minerals Silt- medium grains of minerals Clay- very fine grains of minerals Organic- material in the soil from living or once living things. Inorganic- material in the soil that was never living Humus- another word for organic material

Where does soil come from? Rocks Minerals Organic Matter

The surface of Earth is always changing.

Soil is a thin layer of Earth’s crust that is just as important to life as water. We could not live without it. It takes hundreds of years for a thin layer of soil to form. Soil forms when rocks break down into smaller and smaller pieces.

Soil Layers Topsoil Large plants like trees grow in the topsoil and down into the subsoil. The roots take in water and minerals from the soil and subsoil Subsoil Broken Rocks Bedrock

Depth of Topsoil and Subsoil Layers

Contents of a Healthy Soil Half the mass of soil is air and water.

Soil Has Many Properties Soil is a variety of colors. It is also many different textures and made up of various sized pieces or grains. The biggest grains in soil are sand. The medium sized grains are silt and the smallest grains are clay.

Soil Color Soil color comes from the minerals that are in the soil. Scientist use a chart when studying soil.

Rules for Determining Soil Color

Soil is made of organic and inorganic material. Organic material is anything that is or was living. Leaves and decaying plant matter. Bacteria and fungi Insects and worms Inorganic material is anything that was never alive. Rocks Minerals

What are the main components of soil? Mineral Matter Air Water Organic Matter

Soil Particles Note: clays are microscopic in size !

Sand, Silt and Clay

Difference in Size 2.0- .5 mm .005- .0002 mm Smaller than .0002 mm

Large particles like sand leave large spaces between them called pore spaces. The larger the pore space the faster water can travel through.

Silt has smaller pore spaces so water moves through more slowly.

Clay has extremely small pore spaces Clay has extremely small pore spaces. Water has a very hard time moving through. Plants do not do well. They can become waterlogged.

Clay minerals photographed with an electron Microscope. Note: they are plate or flake like and are stacked on top of each other. They are electrically charged and act like magnets that attract and hold plant nutrients.

Organic matter, or humus loosens the soil and returns minerals back into the soil.

Organic matter is soil gold !

What causes soil erosion? Water Wind Lack of Vegetation

My Neighbor has my soil! Soil with no vegetation to hold it in place is blown away by the wind or washed away by water.

The dust bowl was caused in the 1930’s by removing the grasses of the plains and poor farming methods which allowed the wind to blow the topsoil away.

Clouds of Silt

Wind Erosion removed topsoil

Wind eroded soil

With less vegitation, there is more erosion.

What are the FACTORS that make SOIL? TIME LIVING ORGANISMS CLIMATE More than 100 years LIVING ORGANISMS Animals and Plants CLIMATE Heat and Cold Wind and Rain ROCKS AND MINERALS The weathering, erosion of rocks and minerals make up half the material in soil.

What are some practices Of Soil Conservation? Terracing Strip Cropping Contour Plowing Tilling Wind Breaks Ground Covers

Terracing prevents the topsoil from eroding.

Other methods of soil conservation are contour farming and strip cropping

Contour Farming Contour farming prevents erosion the same way that terracing does.

Minimum Tillage Minimum tillage means not cutting into the topsoil any more than necessary when plowing.

Strip Cropping

Strip Crop Farming Growing crops in alternating fields keeps the topsoil from eroding.

Soil - We cannot live without it!

Give a hand to the land

Which container allows the most water to move through? Why?

Internet Sites http://www.tx.nrcs.usda.gov/class/sammy.htm