Activities

1. Define porosity.
   
   
2. Define permeability.

3. How does particle size affect the permeability of soil?
   
   
4. How is the soil in a desert similar to the soil in a forest?  How is it different?

5. Your friend would like to begin growing vegetables in his backyard.  He said the soil in his yard is dense and feels very sticky.  What type of soil is in your friend’s backyard?  Would you suggest planting a garden with this soil?  If not, what type of soil should your friend use?  Explain your reasoning.

Answer Key/Rubric

1. Porosity is the amount of empty space (air) between soil particles.
   
   
2. Permeability describes how easily water or air is able to move through soil.
   
   
3. Acceptable responses may include, but are not limited to:
   • If the particle size is small, they will be closer together.
   • Particles that are close together have small porosity.
   • The smaller porosity, the lower the permeability.
   • If the particles are large, they will be farther apart.
   • Particles that are far apart have large porosity.
   • The larger the porosity, the higher the permeability.
     
     
4. Acceptable responses may include, but are not limited to:
   • Both contain sand particles.
   • Forest soil probably contains some silt and clay particles.
   • Desert soil is much more permeable.
   • Both have enough organic material and nutrients to support the growth of plants.
   • Desert soil has much less organic material and nutrients.

5. Acceptable responses may include, but are not limited to:
   • The friend has clay in his backyard.
   • Clay is poor for gardening.
   • It has small porosity and low permeability.
   • Clay holds lots of water.
   • The friend should not plant his garden in clay soil.
   • The friend should create soil with a mixture of clay, sand, and silt.
   • The mixture will hold water, but will still be permeable.
   • The mixture will also have adequate porosity for water and air to circulate through.