Card Set Information
What is soil?
Solid earth material that has been altered by physical, chemical and organic processes so that it can support rooted plant life
Why is soil important?
It is the growing medium for our food
Purifies our waste
Home to plants and animals
How long can it take to form one inch of topsoil?
How much can an earthworm work for a year?
A ton of soil
What is soil made up of?
25% is air
What are the factors of soil formation?
How does climate help soil formation?
The greater the rainfall amount, the more rapid the rate of both weathering and erosion
How do organisms help soil formation?
Plant and animal activity produces humic acids that are powerful weathering agents
They stabilize soil profiles and tend to increase erosion
How does parent material help soil formation?
How does topography help soil formation?
Ground slope (the steeper the surface slope, the more likely any eroded material is to be transported out of the system)
- soils on hillslopes reach about 1m thickness while soils on flat surfaces, tend to thicken through time
What does soil thickness mean?
Reflects the balance between rates of soil production and rates of downslope soil movement
How does time help soil formation?
Development and destruction of soil profiles
Typical reaction rates are slow, the longer a rock unit has been exposed, the more likely it is to be weathered
What are the transformations of soil?
Decomposition of organic matter
Humification to form complex organic matter
Weathering of rocks
What is decomposition?
Breakdown of soil organic matter to form soluble compounds that can be absorbed or leached
Primary layers of soil
What is on Ao horizon?
Highly decayed organic material (Humus)
What does humus do?
Gives topsoil a rich brown color
What happens in A horizon?
What is leaching?
Carries minerals down into the lower soil horizons
What is on B-horizon or subsoil?
Where the leached minerals end up
Why do coastal plains have no bedrock?
Instead it has layers of sand, clay and gravel because the sea level changes over time
What is the best soil texture for growing things?
Loam -mixture of clay and silt
Contain a good supply of nutrients, necessary for the organisms living in the soil
Sandy particles - can be seen
Silt - feel powdery and don't hold together when went
Clayey - smallest soil particle
Sieving soil fractions
What are the major nutrients found in fertile soils?
What helps maintain the balance of nutrients?
What is physical weathering?
Breaks rocks into small mineral particles
What is chemical weathering?
Dissolves and changes mineral at the Earth's surface
What is saprolite?
Weathered rock that retains remnant rock structure
What limits soil development?
What do landslides do?
Redistribute and mix material creating uneven surfaces and topographic variability
Methods to control soil erosion
Conservation tillage - crop residues are left in the ground
Contour plowing - fields are plowed in curves
Strip cropping - placing closely sown crop under a loosely sown crop
Terracing - to catch downhill runoff
Shelter belt - to control blowing dust of the semiarid plains
Greenbelts - using shrubs and trees as boundaries