Compost Sorting

1.9 based on 8 ratings

Updated on Aug 07, 2013

Normally, we throw all of our compost into one big pile, and use it to fertilize the garden. However, it stands to reason that different types of compost have different effects on plants. This project may help sort things out. This project examines different compost materials, in terms of their effects on plant growth and quality.


What is and isn't compost? What are the effects of different compost materials on different plants?


  • Computer with internet access.
  • 8 large plastic containers (at least one foot deep and one foot in diameter)
  • Screwdriver
  • Packaged multipurpose potting soil (enough to fill containers)
  • Two kinds of seeds (tomatoes and nasturtiums are recommended)
  • Various composting materials
  • Basic gardening equipment (gloves, shovel, watering can, etc.)
  • Digital camera
  • Typical office/craft supplies (such as paper, pens & posterboard)


  1. Using the screwdriver, poke 3 holes in the bottom of each plastic container.
  2. Put a shovelful of potting soil in each container.
  3. Sort your compost into separate piles, using the plastic containers. Put banana peels in two of them, coffee grounds in another two, etc. Leave TWO containers with ONLY soil (no compost).
  4. Clearly label each container, and leave the containers outdoors.
  5. Check on (or add to) the containers regularly over the next two weeks.
  6. Fill each container nearly full with the potting soil, and mix well.
  7. Plant tomatoes (same kind, preferably from the same packet) in one of each type of compost. Do the same with nasturtiums in the other containers. Avoid overcrowding.
  8. Water plants regularly, maintaining them as indicated on the seed packets.
  9. Observe the differences. Check ripe plants for color, texture, size and taste.
  10. Record all results.
  11. Interpret results in a detailed report.
  12. Show results visually using photos taken throughout the course of the experiment.
  13. Include plant samples in your science fair display.
Judee Shipman is a Bay Area Educational Consultant and professional writer of quality educational materials.  Her recent writing credits include (a popular and entertaining website about states), and a book called The Portable Chess Coach (Cardoza, 2006), currently available in stores.

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