Soil TypesSoil Types

Quick ReviewQuick Review

1. What is the process that forms soil?1. What is the process that forms soil?

- weathering- weathering

2. What are the two types of weathering? What 2. What are the two types of weathering? What causes them?causes them?

- physical (rain, snow sleet, hail)- physical (rain, snow sleet, hail)

- chemical (acids)- chemical (acids)

3. What is another name for a layer of soil?3. What is another name for a layer of soil?

- horizon- horizon

More Review!More Review!

4. What is the name for soil that has a lot of 4. What is the name for soil that has a lot of decaying organic material?decaying organic material?

- humus- humus

5. Which layer is most important for plant growth?5. Which layer is most important for plant growth?

- topsoil- topsoil

6. What is the main cause of desertification?6. What is the main cause of desertification?

- improper management of soil which leads to - improper management of soil which leads to erosion.erosion.

Types of SoilsTypes of Soils

Soil is classified according to the type of Soil is classified according to the type of mineral base and the size of the particles.mineral base and the size of the particles.

There are 3 types:There are 3 types:

1. Sand1. Sand

Very large particlesVery large particles Feels roughFeels rough Does not hold water or Does not hold water or

nutrients well.nutrients well.

2. Silt2. Silt

Particles are smaller Particles are smaller than those in sandthan those in sand

Feels smooth and Feels smooth and powderypowdery

3. Clay3. Clay

Has very small particles, and Has very small particles, and gums together.gums together.

It holds water and nutrients It holds water and nutrients well, but plants roots can’t well, but plants roots can’t grow well.grow well.

While it holds water well, it While it holds water well, it takes a long time for water to takes a long time for water to permeatepermeate a clay soil. a clay soil.

Brief, heavy rains may not Brief, heavy rains may not reach plant roots.reach plant roots.

LoamLoam

Mixture of sand, silt, Mixture of sand, silt, and clay and organic and clay and organic matter.matter.

Water and nutrient Water and nutrient holding abilities vary holding abilities vary with composition.with composition.

Which type is best?Which type is best?

The ideal type of soil for plant (crop) growth is The ideal type of soil for plant (crop) growth is partway between these two extremes.partway between these two extremes.

LoamyLoamy soil has neither too small nor too large soil has neither too small nor too large particles (It’s just right!)particles (It’s just right!)

LoamyLoamy soil has a good percentage of decayed soil has a good percentage of decayed plant material or plant material or humushumus which provide the which provide the nutrients that plants need.nutrients that plants need.

Further ResourcesFurther Resources

National Resources Conservation Service National Resources Conservation Service website. Try out the Web Soil Survey tool to website. Try out the Web Soil Survey tool to see what’s under your feetsee what’s under your feet

US Environmental Protection AgencyUS Environmental Protection Agency Digging to China?Digging to China? Introduction to SoilsIntroduction to Soils