Every soil sample that you touch is different from all others. The best way to find this out is by feeling many different types of soil. Soil has three main building blocks called particles: sand, silt, and clay. These particles combine in many different ways to create multiple combinations of different soil textures. These soil textures are very important in how fast water drains (clays drain slow, sands drain fast), how easy soil erodes (silt erodes easiest). These soil building blocks (particles) start to fit together like puzzle pieces in different shapes called peds. These peds come together, and make up the structure of a soil. Good structure is needed to grow strong, healthy plants.
This activity is suitable for grades 4+.
Lesson Objectives:
1. Get students to be able to feel different types of soils and try to identify what is in it.
2. Be able to define soil texture, and understand what different soil textures mean.
- What are the different particles that make up soil?
- How is a sandy soil different from a clay soil?
- What does sandy soil feel like? Gritty vs Slippery
- How does sandy soil hold water compared to clay soils?
- Do we want soils to hold water better?
3. Understand that there are different types of soil structure
- What type of structure is desirable to have at the surface, and why?
- What is a ped?
- Which type of soil has no peds?
- Be able to identify what a pore is, and why pores are good?
- Which type of structure has the most pores?
- Which type of soil has the least amount of pores?
- Why is the single grained soil not that great for growing plants? Even though the particles stay separate and have a lot of pores?
4. Be able to grasp how humans can change soil structure
- Good structure = healthy soils
- What have your students done that could have harmed the soil?
- Tractors can squish soil, four wheelers, cars, and dirt bikes
- How can students help the soil?
- The best way to keep soils healthy is to keep them covered. What benefits does this provide?
- Erosion control: How does keeping the surface covered prevent erosion?
- Plant roots: Besides erosion control, what else do plant roots provide?
- Why would you not keep them covered?
- In some parts of the country, it causes the soil to be too wet in the spring, especially under clay soils.
- In some parts of the country, it is too cold, and soils take too long to warm up to get a decent crop in.
- How can soil erosion be good?
- Fertility from dust into the Amazon from the Sahara
- Chinese soils blowing into the US.
- The best way to keep soils healthy is to keep them covered. What benefits does this provide?
Glossary Words:
In Current Glossary:
- Soil Texture
- Soil Structure
- Sand
- Silt
- Clay
- Blocky
- Columnar
- Erode
- Peds
- Granular
- Prismatic
- Platy
- Massive
- Single Grain
- Enzyme
Other Glossary Words:
- Soil particles – the individual building blocks that make up soil. The sand, silt, and clay
- Soil traffic – any time a tractor, vehicle, or even a person moves over the soil surface and disrupts it.
Activities or Information:
1) Information
- Soil Types by Texture - Utah AIC
- Water Holding Capacity of Different Soil Structures (Section 4) - University of Minnesota
- Raindrop and Soil Erosion - Soil Erosion Website
2) Activities
- Texture by Feel - Information and Activity on soil texturing.
- Erosion Demonstration - This demonstration shows the effect ground cover has on Soil Erosion
Study Questions:
1) What are the three particles of soil that make up soil?
- Sand
- Silt
- Clay
2) Name two things that people can do to hurt soil?
- Answers can vary - Till when wet, walk on wet soil, dirt bike, four wheel,
3) Help soil?
- Make sure soil is covered, plant plants that grow year round.
3) Name three types of soil peds?
4) What type of soil structure would you want to have in your garden?
