Most of the foods we eat are grown in soil across the planet. These soils differ a great deal due to the rocks that eroded to create it, the temperate and temperature changes that occurred as it developed, rain fall and humidity present as the soil developed, and many additional factors. Soil types are determined by the composition of sand silt, clay and organic matter. Soil types affect the soil’s structure, ability to hold nutrients, water, air, structural support of plants, habitat for animal and microbial life, and more!
This simple activity is an introductory exploration to soil science that can help determine the type and best use of soil.
- Soil sample (about two cups)
- Jar (at least a quart) with a lid
- Soil Type Triangle Diagram can be found on page 119 of the Minnesota School Garden Guide
- Place about 2 cups of soil in a quart jar and fill the jar with water.
- Place the lid on tightly and shake the jar.
- Place the jar on a flat surface and allow the soil to settle completely. The water will be clear when the total sample has settled.
- The soil particles have settled according to size with the largest and heaviest (sand) on the bottom and the smallest and lightest on the top (clay). The middle layer is silt. Using a ruler, measure the total height of the three layers and record this number to the nearest millimeter.
Total height of three layers = ______________________
- Calculate the percentage of the sample that is sand, silt and clay.
- Sand = (measure of bottom layer to the nearest mm ÷ total height of three layers to the nearest mm) x 100 = _______ % of sand
- Silt = (measure of middle layer to the nearest mm ÷ total height of three layers to the nearest mm) x 100 = _______ % of silt
- Clay = (measure of top layer to the nearest mm ÷ total height of three layers to the nearest mm) x 100 = _______ % of clay
- Use the Soil Type Triangle on page 119 of the Minnesota School Garden Guide to determine the name for this type of soil sample.
- Once the soil type is determined, do some research to find out what types of plants grow best in this soil type.
- Collect soil samples from several very different locations (a sandy beach, fertile garden, etc.) and complete the procedure above. Compare the different amounts of sand, silt and clay from these locations.
- Access http://www.nrcs.usda.gov/wps/portal/nrcs/site/national/home/ to examine soil issues in the United States and globally
For a complete “It All Begins with Soil” lesson plan and background information go to the Minnesota School Garden Guide, page 115 .
For further information about the Minnesota Agriculture in the Classroom program visit www.mda.state.mn.us/maitc or contact Al Withers, Program Director at firstname.lastname@example.org or Sue Knott, Education Specialist at email@example.com.