Soil 1/19/23

primary succession

Water, air, and living organisms break down parent material in the lithosphere

parent material (R Horizon)

1. Hardened lava or ash
2. Sediment deposited by glaciers or water
3. Windblown dunes
4. Bedrock is the solid rock that makes the earth’s crust

what breaks down parent material?

weathering

humus

partially decomposed matter on top of soil

parent material + weathering

creates smaller particles of parent material

how many types of weathering are there?

Three

physical weathering

wind, rain, thermal expansion and contraction, water freezing

chemical weathering

water and gases

biological weatherings

tree roots and lichens

particle size

Determines the amount of air & water contained in the soil

Scale (From Largest to Smallest)

Large, Coarse pebbles→

Medium, coarse pebbles→

small, fine pebbles→

finest pebbles→

quartz sand

soil horizons

a distinct layer of soil

soil profile

the cross-section of soil as a whole, including all soil horizons from the surface to bedrock

leaching

the process by which minerals are dissolved in a liquid and transported to another location

Soil Profile

O Horizon (Litter Layer)

organic matter deposited by organisms

A Horion (Topsoil)

organic material mixed with mineral components (salt, etc.)

E Horizon (Eluviated, leaching layer)

minerals and organic matter tend to leach out of this horizon

B Horizon (Subsoil)

minerals and organic matter accumulate here

C Horizon (Weathered parent material)

initial step in soil formation

R Horizon (Rock, parent material)

bedrock, lava, etc.

Soil Texture Chart

soil texture

determined by percentage of sand, silt, and clay

clay (smallest)

few pore spaces, sticky, difficult for air and water to pass through

silt

more pore spaces than clay, less pore spaces than sand

sand (largest)

water passes through quickly

loam

even mixture of sand and clay, best for agriculture

porosity

the pore space within a soil (more sand, more porous)

permeability

how easily water drains through the soil

H2O holding capacity

how well water is retained, or held by a soil

effects on soil fertility

different soil textures have different effects on soil fertility

when soil is too sandy

drains water too quickly for roots and dries out

when soil has too much clay

doesn’t let H2O drain to roots, or waterlogs (suffocating them)

when soil is just right (loam)

The ideal soil for most plant growth is loam, which balances porosity with H2O holding capacity

soil fertility

soil’s ability to support plant life

factors that increase soil nutrients

* Organic matter
* Humus
* Decomposer activity
* Clay
* bases

factors that decrease soil nutrients

* Acids leach positve Charge nutrients
* Excessive rain/irrigation Leeches nutrient
* Excessive farming depletes nut. 
* Topsoil erosion

factors that increase H2O holding capacity

* Compacted soil
* Topsoil erosion
* Sand 
* Root loss

nutrients for plants can be provided by

1. Inorganic fertilizers
2. Organic fertilizers (compost)