Soil

AIM: How is soil made?

How to Make a Mud Pie video

1. What role does weathering play in the formation of soil?

Soil forms as rock is broken down by weathering and mixes with decayed organic matter (humus).

2. What are the different materials that make up the soil?a. Weathered rock

pieces provide mineralsb. Humus = dead organic

matter provides other nutrients,makes soil fertile

c. Air – the soil is aerated when worms dig holes

d. Water

3. How do plants and animals help the formation of soil?

a. Organisms (like worms) mix the soil and make spaces in it for air and water.

b. Microbes (decomposers) decay dead organic matter.

c. Dead organic matter is humus = the material that makes soil fertile to grow crops.

Soil profile: Layers are called horizonsO-Top Soil: Humus and Minerals, most fertile

A-Subsoil: little organic matter

B- Partly weathered rock

C-Un-weathered bedrock

Why is the bedrock un-weathered?

There is little water, animals, wind, and ice to cause weathering down that deep in the ground.

A

B

C

darker

lighter

Which layer contains the most biological material and why?

Why is layer D predominantly unweathered bedrock?

What 2 processes are responsible for the formation of the dark brown topsoil layer?

4. There are different types of soil based on types and percentages of sediments.

a. Loam – clay, sand and silt

b. Best for growing most types of plants

5. What factors increase the rate of soil formation? Climate (water and temperature)

Soil formation happens faster in warm, damp climates

Rock type (size and composition) Softer rocks will break down faster

…just like weathering rocks!

6. Leaching – surface water and rain seeps down into layer below topsoil and

carries minerals from top layer.

8. Why is soil important?

a. All living organisms depend directly or indirectly on plants (producers) that grow in soil.

b. Because it takes a very long time to form, soil needs to be conserved. It is not easily renewable….soil is limited.

c. How Much Soil Is There?

9. How did the settlers create the Dust Bowl?

Turning the Great Plains to farms and ranches, they removed the sod and

grass that held the soil in place. (desertification) Drought dried out the soil turning it to dust.

Dust Bowl, Memories Australian Dust Storm

10. What are some techniques farmers use to conserve soil?

a. Limit cattle grazing to prevent desertification, where all of the vegetation are stripped from the land

b. Contour Plowing– to avoid runoff andsoil erosion, crops areplanted in parallelrows to contours of land

c. Strip cropping – alternating low crops between other crops to create natural dams

d. Crop rotation – ex. Don’t plant tomatoes in the same plot every year, rotate where they are planted. This avoids depleting soil of nutrients.

e. Wind breaks – planting lines of trees to keep wind from blowing away soil

11. What are some actions you can take to encourage soil formation?a. Composting – pile up

grass clippings, leaves, vegetables and newspapers to create a fertile pile of soil

b. Mulching lawn clippings and leaving them on the ground

c. Don’t rake up all the leaves

Brainpop - soil

http://www.brainpop.com/science/earthsystem/soil/