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Fill Your Decomposition Column

Choosing ingredients: Decomposition Column ingredients can include leaves, grass and plant clippings, kitchen scraps, newspapers, animal manure and soil. If you are interested in how fast things decay, try building two identical columns, but fill them with leaves from two different species of trees. Try adding fertilizer to your column, or water from a pond or river. How do you suppose differences in temperature, light or moisture will affect the decomposition process?

The time it takes: You'll begin to see mold and other evidence of decomposition within the first few days after filling your column.

Two or three months is plenty of time to see soft organic material such as leaves, fruits, vegetables and grain products decompose dramatically. (The term organic applies to something that is derived directly from a living organism.) Bark, newspapers and wood chips all take longer to decompose, though they still undergo interesting changes in two to three months.

How wet?: Keep your column moist in order to observe more rapid decomposition. Avoid flooding your column or it will become waterlogged. This can create an anaerobic environment, or one completely lacking oxygen, in which certain microbes create particularly vigorous odors.

Using your nose: Odor is a by-product of decomposition, and can tell you a lot about the materials in your columns. Odors may be strong at first, but can mellow and become musty with time. Classrooms full of odorous Decomposition Columns, however, have been known to try the patience of colleagues and building supervisors. The strongest odors arise from animal products such as meat and dairy products. Grapefruit rinds and grass cuttings can also produce strong odors. Why is this so? If you use food scraps, mix in plant matter such as leaves, twigs and dried grass to temper odors. Layering soil on top of contents also lessens the odor.

Increasing the number and size of air holes in your column will increase air exchange. How do you think this will affect decomposition? Keep holes small so fruit flies stay inside.

If your classroom fruit fly population booms anyway, make a Fruit Fly Trap!

National Science Foundation   Bottle Biology, an instructional materials development program, was funded by a grant from the National Science Foundation administered by the University of Wisconsin-Madison.   Wisconsin Fast Plants