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Super Soil

Use a simple alum-profile test to compare local soils with a commercial garden mix for organic content.

Group Size: This activity is suitable for both large and small groups.

Suggested Age: 10 and up

Time: Allow forty to fifty minutes for this activity.

Site: Areas with lots of bare, hard ground (such as vacant lots, school fields, or your backyard) are excellent sites for Super Soil.

Safety: No specific consideration.

Materials/Prep: For each team of two: 2 clear plastic vials about 1” in diameter and 2” high, 1 digging tool, 1 cup of commercial garden mix, 2 cups of organic material (manure, compost, peat moss, of leaf mold). For the group: 1 waterproof pen, 1 small jar of alum, paper towels, 4 liters of water or a water source

Focus questions:
How does the amount of organic matter in the backyard soil compare to the amount in commercial garden-mix soil? How would you make your own organic-rich soil?

Learning outcomes:
  • Organic matter consists of plant and animal material that bacteria are breaking down into smaller parts.
  • The process of breaking down organic matter is called “decay” or “decomposition.”
  • Soil with lots of organic matter will hold more air and water and will have more nutrients for plant growth.
  • Different types of soil have different amounts of organic matter.
  • An alum-profile test can be used to determine the amount of organic matter in a sample of soil.

The kids collect a soil sample from their school ground, backyard or other source. They use the alum-profile test to compare the amount of organic matter in their sample with a sample of commercial garden soil. They determine how much organic matter (compost, manure, or leaf litter) they must add to the local soil to match the organic content of the commercial mix.

Isn’t It Amazing:
Soil is alive. A cubic centimeter of soil generally contains between 20 million to 200 million bacteria. That is as much mass as two cows for a football field-sized plot. The bacteria are an essential component of productive soil, because they break down organic matter and release the nutrients, in holding nutrients in their cells that can be used by the plants, convert nitrogen from the air into a form that can be used by plants, break down pesticides and pollutants in the soil, maintain a bacterial balance in the soil that reduces plant diseases, secrete substances that help protect plant roots, and help retain water in the soil.

Extension Activities:
1. Let the kids take the equipment home to do alum test in their own backyards.
2. Ask the kids to mix their own good soil and then plant seeds or seedlings in it. Here are some planting instructions: a. Cut one side out of a half-gallon milk carton, and then staple the spout closed. b. Poke two holes in the bottom of the carton for drainage. c. Fill the carton nearly to the top with your homemade soil. d. Plant seeds or seedlings, and water them. Peas, beans, lettuce, and Swiss chard are easy to grow. e. Water regularly, but don’t over water.



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