Soils The dirty truth!

What is soil and how is it made? m/soil/ m/soil/ Check out the FYI

We can’t live without it All land life depends on it There isn’t very much good soil available on Earth (apple demonstration) Required to grow plants All animal life on land depends on plants

What is Soil? Air—about 25% Water—about 25% Minerals—about 45% Decayed organic material--varies

Soil is a mixture of what four materials? A.Granite, limestone, nitrogen, and air B.Rock particles, humus, air, and water C.Rock particles, plant roots, humus, and nitrogen D.Plant roots, iron oxides, water, and air

Where does soil come from? All soil starts from rock. Rock that has never been worn down is called bedrock. Rock must weather (break down) into smaller and smaller pieces Rock can break down in two ways. – Chemical weathering – Physical weathering

Chemical and Mechanical Weathering weathering/ weathering/

Weathered Rock Weathered rock doesn’t stay put, but is usually moved by erosion Erosion can happen from wind water ice

Erosion m/erosion/ m/erosion/

Soil Horizons Soil has layers First the C layer forms Next the A layer Last the B layer

Soil formation from Bedrock The topsoil (A horizon) has the most humus. The weathered rock layer (C horizon) has the least humus. Active Art on soil formation

Characteristics of Soil (how we can describe soils) Color Particle Size Texture Consistency pH Moisture Temperature

Soil Color Two sources of color in soils Minerals in the soil: for example. red clay soils have a lot of iron; brown/black soils have manganese….different minerals have different colors Mica is dark Quartz is light Hematite is red

Soil Color, continued The more organic material, the darker the soil. Organic material comes from dead plants and animals. Organic material in soil is called humus. Humus is THE most important factor in soil color. The more humus, the darker the soil.

Soil color can tell a lot about the contents of soil. According to the graph of soil profiles, what inference, or guess, could you make about soil sample “C”?

Where do you think soil sample “B” came from? A.The top layer of soil B.The middle layer of soil C.The deepest layer of soil D.Depth of soil does not affect its color

Soil Particle Sizes Sand—smaller than gravel, you can still see it, feels grainy, water flows through easily Silt—smaller than sand, can’t see individual particles, feels smooth like powder, water has a harder time flowing through Clay—smaller than silt, feels sticky, water usually doesn’t flow through

Sedimentation Tube See Demonstration

Clay pot soil Activity Soil texture means how much of each size particle is in soil Are you sand, silt or clay? Sand lets water flow quickly through, while clay holds water and won’t let it flow

Which soil sample will hold the most water? A.Soil sample A will hold the most water B.Soil sample B will hold the most water C.They will both hold the same amount of water D.Only silt can hold water

Consistency Soil consistency means how the soil likes to stick together. It depends on the kinds of minerals in the soil and how much water is in the soil Does it stick together when you squeeze a handful of it? Does it crumble apart? Is it sticky?

Soil pH pH is the way we measure how acid or basic something is It usually ranges from 0 to is very acidic while 14 is very basic, 7 is neutral like pure water Acids: lemon juice, orange juice, sodas Bases: Clorox, ammonia, baking soda

Some Plants like acid soils

Other plants like basic soils But if soil is too acid or basic, no plants can grow

What does the pH level do? pH of the soil affects how minerals dissolve. The best pH for soils and plants is between 6- 7, slightly acidic. At this pH, the nutrients from minerals become available to plants. The water in the soil will dissolve the nutrients from the minerals in the soil! Happy plants!

Nutrients Nutrients are the chemicals that an organism needs to grow or maintain its life.

The pH of soil helps to A.Hold water for plants B.Produce minerals C.Increase pore space D.Dissolve nutrients for plants

Soil moisture Plants need moisture. If soil is too dry, plants won’t grow. If soil is too wet, plants won’t grow. Moisture must fall in a range for plants to grow. too wet too dry

When soil becomes too dry, it can more easily erode in the wind. An important example of this is the Dust Bowl from the 1930s. A drought in the plains states, along with poor farming practices, caused heavy erosion of topsoil.

Dust Bowl, cont. Dust bowl lasted 10 years! It took place in the southern Plains States

United Streaming Dust Bowl Video ?guidAssetId=92FA06A9-396A-4919-B9CC- 4FEE B&blnFromSearch=1&productco de=US

Soil temperature If soil temperatures are too high or low, plants can’t grow

Review of Good Soil Dark in color means high nutrients, both organic (humus) and inorganic (mineral) Not too dry or wet Slightly acidic pH Not too much sand or clay Deep layer of topsoil

Soil is so valuable…. How do we protect it? Good farming practices Contour plowing-when plowing around a hill, make rows around the hill, not up and down!

Conservation plowing Don’t plow unless you need to. When soil isn’t plowed up, it doesn’t wash or blow away as easily Plowing creates loose soil. Not plowing keeps plants in the ground and roots lock soil into the ground

Crop Rotation If you plant the same crops in the soil year after year, the soil loses nutrients. Plants won’t grow as well in that soil after years of this kind of farming

To avoid it, you should plant different plants in an area every few years. This is called crop rotation

Aaron noticed that when the fields were plowed, a lot of soil was blowing away in the air. If the amount of plowing DECREASED, which statement would probably be true? A.The amount of soil lost each year will not change B.The amount of soil lost each year will decrease C.The amount of soil lost each year will increase D.New soil will grow to replace lost soil

Bob’s farm is on a hillside. How can contour plowing (plowing along the curves of the hill) help conserve the soil on the hillside? A.Contour plowing allows rainwater to run straight downhill which helps shift the soil sideways. B.Contour plowing block rainwater from running along the curve which helps soil to flow downhill C.Contour plowing allows rainwater to run along the curves which helps to keep soil in place D.Contour plowing blocks rainwater from reaching the plants which helps conserve soil nutrients.

Without Protection, Soil…. can wash away in a mudflow following heavy rains

can erode and deposit in a new place

can create landslides

and can slump

Active art on soil movement

Summary of Soil Conservation Don’t leave soil bare, keep plants in the soil Use conservation and contour plowing techniques Rotate crops that are planted so nutrients stay in the soil

Which of the following could help prevent soil erosion? A.Planting tree between fields B.Strip mining and open pit mining C.Building highways and shopping malls D.Cutting down all of the trees