Activity: Earth(worm) Movers

Purpose

To observe the major role earthworms play in breaking down plant matter, creating fertile, well-aerated soil.

Overview

Students will participate in making a worm column using soil samples, leaves, grass, worms, 2-liter bottle(s), newspaper clippings, a large brown paper bag, and water. Students will observe how earthworms affect the appearance of soil layers overtime. Burrowing earthworms will mix and aerate the layers of soil, raise the organic matter, and bring deeper soil and nutrients to the top. The mixing and aerating of soil is important for water and plant root penetration.

Time Required

Material preparation is dependant upon time it takes to collect four to five soil samples and to obtain supply of red worms. Collection of leaves, grass, and other organic "feed" material will be periodic.

Worm column construction- 30 minutes
Worm composting process - 2 to 3 weeks minimum
Every 3 to 4 days check food level, temperature, soil properties, and worm activity.

Skill Level

All (Teachers will have to provide a more completely prepared worm column for younger students.)

Key Concepts and Skills

Concepts: Activities worms perform in the soil: mixing, aerating, decomposing), soil formation, understanding biological activity in soil
Skills: Reasoning, observing, predicting, determining differences in soil by color and texture

Materials and Tools

one 2-liter bottle
one bottle base from another 2-liter bottle or similar shaped container to be used as a top
one large brown paper bag, or one 25 cm x 40 cm sheet of brown paper used for a screen
wax pencil, marker, or crayon for drawing cutting lines on plastic
utility knife to begin cut on bottle and scissors to finish cut
large needle or pin to make air holes in plastic
thermometer (Celsius)
5-10 red worms (or local worms)
worm food: organic leftovers from kitchen garden, or yard (e.g. grass, leaves)
worm bedding: shredded newspaper, shredded leaves
four to five soil samples of different colors from local area (try to get an A horizon (topsoil), B horizon (subsoil), potting soil from store, soil near stream or on different parts of slope to get different colors); remove large rocks and other debris

Procedure

Prepare a worm column by using one 2-liter bottle, with 10 cm of the top removed and the entire base removed, if present. The base of the first 2-liter bottle can be used if it is removed carefully; otherwise, carefully remove the base of the second 2-liter bottle or obtain a similar shaped container to be used as a top for the worm column.
Poke four 5 mm drainage holes with a large nail low around the base. Poke two rows of eight 3mm airholes approximately one- quarter of the way down from the top of worm column.
Cut the brown paper and encircle the cut 2-liter bottle allowing about 4 cm of the brown paper extending above the bottle. Tape the paper around the column, leaving it somewhat loose so this cover can easily be pulled up. Worms prefer darkness, so leave the brown paper screen around the bottle until it is time to observe the worms performing their work.
Prepare newspaper bedding: Cut 2-3 pages of newspaper into 0.5 cm strips, then cut these strips in half crosswise. (This will provide enough newspaper bedding for two worm columns.)
Add 200 to 300 mls. of water (1-2 cups) to the bedding, then fluff the bedding vigorously until paper strips are well separated. Add a small handful of soil into the bedding, to introduce natural microorganisms into the soil, which will break down the newspaper.
Fill the worm column two-thirds full with prepared bedding from step 4. Ensure that the bedding is moist but not saturated with water. Test the pH of the bedding. Worms prefer a neutral to slightly basic environment (pH of 6.5-8.5). If your prepared bedding is acidic, mix in powdered lawn lime or finely crushed eggshells and test bedding again.
Place 5-10 red worms onto bedding, inside worm column. Let the worms exist in this bedding environment for a few days, keeping the temperature of the bedding around 25 degrees Celsius.
After a few days, add layers of different colored soil samples to the worm column by carefully placing each separated layer atop the bedding. Do not mix the soil samples in with the bedding. The layering of the soil samples should easily be seen from outside the worm column. Periodically check that the temperature of the column stays within 20 to 25 degrees Celsius.
Add enough water from the top of the column to moisten the soils and allow them to settle (do not saturate the soils).

Maintenance

Feeding the worms: Add moist organic food every 3-4 days to the worm column by placing 1-2 cm sized pieces atop the bedding. Then, add approximately 1-2 cm of moist bedding atop the moist worm food. Ensure that the food is being eaten before adding more food to the worm column. Worms eat 2 to 3 times their mass of food every few days (approximately 25 to 50 grams of food for 5 to 10 worms). If in doubt, it is better to underfeed your worms.
Check that the temperature of the column stays within 20 to 25 degrees Celsius.
Every few days, remove the paper cover from around the bottle and observe the results of worm activity? Have the soils in different layers been mixed? Can you see traces of worm channels? Can you see holes or spaces where the worms have been active? What have the worms done with the food from the surface? Record and discuss your observations.

OPTIONS:

prepare a second column, but omit the worms. Compare the two columns over time.
prepare a column with another type of worm and compare what happens inside the columns over time.
Prepare a larger scaled composting container using five gallon buckets. Use a hand drill to make aeration holes 1 cm in diameter, fill the container half full of moist bedding material, add organic material to feed the worms as needed, and keep the lid on the bucket to keep light out and moisture in.

To obtain worms

Dig in a local area and collect the worms you find. Red worms are available from bait shops in local area or order through: Flowerfield Enterprises, 10332 Shaver Road, Kalamazoo, Michigan 49024-6744. (616) 327-0108 or fax (616) 327-7009. An information brochure is available, as well.

Last updated: 2/1/97; Comments? globe@hwr.arizona.edu