SOIL What’s the dirt on dirt?. Why study soil in environmental science??? Soils are the foundation...

SOILWhat’s the dirt

on dirt?

Why study soil in environmental science???

• Soils are the foundation for ecosystems.

• Understanding soils and the organisms that rely on it allows us to understand how human activity can affect those organisms– For example….• Waste, Construction, Mining, Deforestation all affect

soils

Importance of Soil

• “Essentially, all life depends upon the soil…there can be no life without soil and no soil without life; they have evolved together.”

• Charles E. Kellogg, USDA Yearbook of Agriculture, 1938

What is in soil???

• Air

• Water

• Humus – dead organic matter (animal & plant remains/feces)-Organisms

• Rocks

• Minerals

How Rocks Become Sediments (soils)

Rocks can be broken down from their parent material and transported to far away new locations and deposited. The processes that accomplish this are called weathering, erosion and deposition.

http://www.youtube.com/watch?v=oFnpm4SUF7I&feature=related

Ex: plants and animal burrowing, wind-deserts, running water, gravity (falling rocks), waves-beaches, frost wedging (water gets in cracks, expands when it freezes causing wedges to open rocks.

Weathering: the break down of rock, minerals or soils through physical or chemical means.

Mechanical: the physical break down of rock through friction and movement

Gravity can also weather rocks. See all of the fallen broken rock piecesat the base of Mount Rushmore.

Water rounds rocks

Cleopatra’s Needle

Burrowing Animals expose rocks

Chemical weathering: breaking down rock by chemicals and chemical reactions.Ex: rainfall, acid rain

2. Erosion: movement of sediment and rock particles from one location to another.

Examples: wind, water (rivers, waves, waterfalls), gravity, glaciers

3. Deposition: depositing materials in layers by dropping the sediments and particles in a new location. Wind or water lays down sediments

Examples: gravel, beaches, sand bars

The Deltas of rivers- slow water flow where the river meets the ocean causes sediments to sink

Aerial view of the Mississippi delta

So what do we do with the soil once it is formed???

• Soil is used to support plant life – the base of the food chain and original food source for all other organisms

• Plants need…– Sunlight (from the sun)– Water (retrieved from the soil)– Nutrients (retrieved from the soil)

Soil fertility

• This gives an indication of the quality of the soil. • A measure of the ability of soil to provide plants

with • 1) sufficient amount of nutrients (measured by

nutrient holding capacity) and • 2) water (determined by porosity, permeability

and percolation), and • 3) a sturdy place for plants to anchor their roots

Nutrient Holding Capacity

• A soil’s ability to hold on to nutrients long enough for plants to absorb them

• Nutrients include nitrogen and phosphorous

WATER

• As discussed, water is also necessary for plants to grow. Soil plays a role in water availability to plants. Ability to provide water is determined by porosity, permeability and percolation.

In order to discuss this you must first understand the following:1. Porosity:

• the volume of water/air the soil (spaces between the rock particles) can hold. The more porous a rock is, the more water it can hold.

Gas/Air filled pore

Water/pollution filled pore

Soil porosity doesn’t describe how well water or other liquids move through soils. Permeability addresses this concept.

2. Permeability: the ability for water/air to flow through the rock

For example-gravel and sand are very permeable. Clay and granite are impermeable.

Percolation (infiltration): water tickling into the ground; a liquid

(water) passing gradually through small spaces or a porous substance

(soil).

• Soil depletionNutrient-rich soil being removed from an area and not

replaced so plants are not able to grow as well or not at all. It can be caused by over-farming, deforestation, etc.

Deforestation and overgrazing are causing soil depletion, erosion and desertification throughout Western Asia and many other parts of the world.

SANDY SOIL

• Porosity – Low – it can hold air but not water

• Permeability - High

• Nutrient Holding Capacity - Low

CLAY SOIL

• Porosity – Low – it can hold air but not water

• Permeability - High

• Nutrient Holding Capacity - Low

LOAM SOIL

• Porosity – Medium

• Permeability - Medium

• Nutrient Holding Capacity - High

With soil made from weathering rock, LAND that is now made can be used.With optimal water and nutrient holding capacity, plants can be grown for food, clothing, oxygen and more.