The Dirt on SoilFormation, Composition, and Characteristics

Why is soil important?• All crops, livestock, and commodities are

dependent upon soil and its fertility.

• All terrestrial life on earth depends on soil and its products to live.

• Soil acts as a filtration system for the hydrologic (water) cycle.

Soil FormationThere are 5 factors:

1. Weather/Climate2. Underlying Geology3. Biological (living)

organisms4. Topography (lay of

the land; slope)5. Time (soil forms at 1

cm per 250-2500 years)

5 Functions of Soil• Provides a medium

for plant growth.• Anchors roots.• Supplies water to

plants.• Provides air for

breathing of roots• Furnishes minerals

for plant nutrition.

What is soil composed of?• 45% minerals (broken down rocks)

– Minerals or rocks break down due to air and water erosion and chemical breakdown due to freeze/thaw action.

• 5% organic matter (dead/decaying plant material)– Organic matter adds nutrients to the soil.– Organic matter is broken down by worms,

bacteria, protozoa, snails, ants, slugs, crickets, sow bugs, etc.

What is soil Composed of? (part 2)

• 25% water– Water comes from

precipitation (rain/snow/sleet/hail).

• 25% air– Air fills the spaces

between the particles, until it is forced out by water.

Soil Aspects

• Soil Types- Soil types vary greatly and affect agricultural practices such as:

» Irrigating

» Fertilizing

» Mechanical Operations (discing, plowing, cultivating)

» Types of plants that will grow

Soil Aspects Terminology• Texture: The texture of the soil is named after the type

of particle that is predominant (most common) in the soil. Texture is influenced by permeability, porosity and erodability.

• Particles: Sand, Silt, and Clay

Soil Aspects Terminology

• Soil Naming: Each soil is named after the town where it was first described. (Example: Antigo Silt Loam, Antigo, Wisconsin)

• Physical Properties: Color, texture, drainage (infiltration rate), structure, depth.

Soil Terms

Composition- The way something is put together.

Decomposition- To separate into smaller, more basic elements or parts.

Parent Material- The matter from which the soils originally formed.

Soil Terms (page 2)

Weathering- The physical disintegration, and chemical decomposition of the soil materials at or beneath the earth’s surface.

Soil Texture- The fineness or coarseness of the soil.

Soil Depth- The amount of soil that is available to plants.

Soil Terms (page 3)

Stratification- To be arranged in levels of differing sizes.

Aggregation- The collection of parts into one body/form.

Soil Color- A primary indicator of soil characteristics.

Soil Structure- The way soil particles are arranged.

Soil Terms from textbook• Soil• Soil Nutrients• Soil Acidity• Soil Alkalinity• Cation Exchange• Chemical Fertilizer• Organic Fertilizer• Ammonification• Nitrification