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Activity 42: Magical Microbes
Grades: K-8
Associated Lesson Topics:
National Standards:
- SCIENCE:
Standard A, Standard C, Standard F
Planting the seed...
Name some things that you threw away today. Did all of these things
really need to go into the garbage? Where does the garbage go when it
leaves your house? What will happen if we run out of places to put our
garbage? Can you think of some ways to reduce the amount of garbage that
we produce?
Teacher Information:
Several times in this course we have recommended that you take a field
trip to explore the dynamic forest ecosystem with your students. Here's
another natural wonder to introduce while you are there: a rotting log.
Most students will immediately recognize the object in question, but won't
necessarily understand the complex processes taking place within the log.
Simply put, the log is turning into soil right before their very eyes!
This is called decomposition,
or the breaking down of organic matter into humus.
In this yearlong project, students will mimic this process through composting:
the speeding up of the decay process that Mother Nature has already mastered.
If you are introducing this concept in the classroom rather than in the
forest, initiate a discussion on the world's current waste problems. This
discussion can revolve around landfills and the problems associated with
them. Encourage students to think of alternatives. This topic can easily
be integrated into a lesson on population growth or environmental problems/solutions.
Whether you teach in an urban, suburban, or rural setting, composting
is feasible. Below, we offer suggestions on how schoolyard and classroom
gardeners can successfully carry out a composting project.
In order to successfully convert garbage to gold, microscopic organisms
need organic matter and the appropriate amount of carbon dioxide, oxygen,
moisture, heat, and time. The primary consumers-microorganisms such as
bacteria, molds, and fungi-quickly move in to consume the organic matter.
In an outdoor compost pile, secondary and tertiary consumers-mites, millipedes,
insects, sowbugs, earthworms, and snails-do the remainder of the work.
With the indoor alternative, called vermiculture,
worms are responsible for breaking down the majority of organic matter.
If the composting procedure is carried out properly, the end result is
a wonderful, nutrient-rich product that can be mixed with soil to enhance
growing conditions for your plants-indoors and out. What a great way to
teach your students about natural cycles! In its finished form, compost
is rich in nitrogen, phosphorus, and potassium. In addition, compost releases
these nutrients slowly and they aren't easily leached away by water.
Necessary Materials and Procedure:
1) Classroom gardeners
For those of you doing the majority-or all-of your gardening in the
classroom, we recommend vermiculture-a composting system that involves
worms. The worms are kept in a box and, if properly cared for, will digest
the food scraps and plant waste produced in your classroom-without producing
an odor. This system provides a wonderful opportunity for students to
observe the decomposition process as it takes place.
Necessary Materials:
- Rubbermaid or Tupperware container with lid.
- Optional: Supplies to build a wooden compost bin, if desirable.
- Drill with 1/16-inch bit.
- Tray to catch drainage water.
- Old newspaper / Brown fall leaves.
- 2 pounds of red wiggler worms (Eisenia foetida). These worms
are commonly sold as fishing bait.
- Food scraps / plant waste.
Procedure:
- First, you and your students will need to make a classroom compost
bin. A large Rubbermaid container with a lid will work fine. Drill SMALL
holes (1/16 inch) along the top rim for ventilation and all over the
bottom for proper drainage (See diagram). Place a tray under the container
to catch drained-off water. This water will be rich in nutrients and
can be used as plant fertilizer.
- If you are feeling more adventurous (or would like to incorporate
mathematical principles into this project), you and your students can
build a wooden compost box. The box should measure 4 feet long by 1
foot high by 1 to 2 feet wide. Since worms like it dark, you will need
to construct a lid for your box. It is easiest if the lid is on hinges.
Remember to drill holes in the bottom of the box for drainage. The wooden
compost box will absorb some of the water and, as a result, will not
produce as much water as the Rubbermaid container. There is no need
to drill ventilation holes.
- The remaining steps should be followed regardless of which type of
compost bin you are using. Shred up the old newspapers and fall leaves
(or peat moss or cardboard) to make the bedding for the worms. The resulting
compost will be richer if you vary what you use for bedding. Moisten
the bedding and place it in the compost bin. This layer should be 8
inches deep.
- Add the worms to the compost box. Two pounds of worms can handle one
pound of food scraps each day. The worms will burrow down into the newspaper
after about 1 hour. Once this has happened, they are ready for your
food scraps and plant waste.
- Review with students what can and cannot be composted. Foods to be
avoided include meat, bones, milk, fatty substances (mayonnaise, butter,
cheese, peanut butter), seeds, and fruit pits. These are the products
that are likely to attract critters and produce foul smells. Have students
make signs for the classroom and cafeteria listing these non-compostable
foods.
- Ask students to bring their food scraps, other than the above-mentioned
ones, back from the cafeteria to the classroom after lunch. Provide
a sealed container in the classroom to collect these scraps and your
plant waste.
- Dig a hole in the bedding. Place the food scraps and plant waste in
the hole and cover it back up. Bury the food scraps and plant waste
in a different spot each time.
- Keep the composting material moist, but not wet.
- After three to six months, you will begin to notice that the bedding
is gone and finished compost is all that remains. There are two ways
to separate the worms from the compost. One way involves dumping the
compost onto a large tarp and having the students manually separate
the two. Alternatively, you can push the finished compost to one side
of the bin and place an 8-inch layer of bedding in the other side. Add
food scraps and plant waste to the bedding side only. After about one
month, the worms will migrate from the compost side to the bedding side,
at which point the compost can be scooped out.
- Add the compost to your potting soil and watch your plants thrive!
- If the bin begins to smell or fruitflies become a problem, you are
probably overloading it with food. Stick as closely as possible to 1
pound of food per day to prevent problems. Remember that the worm population
will reproduce, making the population larger, eventually enabling more
food to be handled.
2) Schoolyard gardeners
If you have the space in your schoolyard, we recommend an outdoor compost
pile. If you are planning to compost food waste, the pile should be contained
within a barrier to prevent animals from inhabiting it. These barriers
can be made of wire fence, wood, concrete blocks, or brick. On the other
hand, if you are planning on composting only garden waste, you can have
an open pile.
Necessary Materials:
- Optional: Wire fencing, wood, concrete, or brick if an enclosure is
required.
- Vegetative brush.
- Nutrient-rich substance (manure, bloodmeal, cottonseed meal). These
can be purchased from your local garden supply store.
- Pitchfork.
Procedure:
- First you must decide what you plan to compost in your pile. If food
scraps will be involved, plan to construct a contained area. The simplest
containment system can be made from wire fencing (see diagram). Alternatively,
you can build a box measuring 3 feet by 3 feet by 3 feet of wood, concrete,
or brick (see diagram). If you are planning on composting only garden
waste, the pile can be in an open area and should measure 5 feet wide
by 3 feet tall. This pile can be as long as desired.
- Begin the compost pile with a layer of brush.
- Next, add your garden waste. This layer should be approximately 6
inches deep.
- Add 2 inches of manure or some other nitrogen-rich substance such
as bloodmeal or cottonseed meal.
- Finish off with a thin (1/8 inch) layer of topsoil.
- Repeat these layers as many times as needed. If the pile reaches 3
feet in height, stop adding to the top of the pile and begin making
the pile longer. This will allow the composting process to occur as
efficiently as possible.
- The pile should be kept moist, not drenched. At this point the primary,
secondary, and tertiary consumers will move in and begin to consume
the organic matter. The pile will heat up as a result of their activity.
Heat is also generated from the sun and outdoor temperature. If the
temperature of the pile exceeds 160F, the microorganisms will die. To
prevent this from happening, the pile must be turned every three weeks.
To turn the pile, use a pitchfork to move the organic material on the
inside of the pile to the outside and vice versa.
- The compost should be ready for use in approximately three months.
- Complete the cycle by adding the finished compost to your garden soil
and enjoy the benefits!
Harvesting the Crop...
How are the food products in our compost pile/box being converted
into soil? Who are the key players and what are they doing to achieve
this result? Why is the resulting soil so high in nutrients? Other than
the rotting log, where else in nature are microbes doing their thing?
What would happen in the natural world if we didn't have microbes?
Note: If you and your students are motivated, your class could begin
a schoolwide composting project. Your students could design a system in
which all of the food waste from the cafeteria is composted. This would
require conducting a "waste watch" to determine how much waste the cafeteria
produces and, consequently, how much waste your composting facility needs
to be able to manage.
Would you like to know more?
Additional Information
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