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Nov. 11, 2010

Decaying Science

by Science Friday Education

Click to enlarge images
Steve Schiro, Milwaukee Projects Assistant at Growing Power, a nonprofit that helps people grow their own food in earth-friendly ways, reveals his love for the red wiggler worms he raises. Find out how worms transform food and plant waste into rich soil.
 
In this activity, students will discuss the difference between organic and inorganic material, and how this distinction affects decomposition. The lesson will culminate with students building a composting column of soil and shredded organic material so that they can observe the decomposition process over the course of three to five weeks.
 
Grade Level: 6th – 8th grade
Subject Matter: Life Science
National Standards: NS.5-8.1, NS.5-8.3

SciFri Video: Worms at Work
 
Steve Schiro shows off his squirm of red wiggler worms (which differ from the earthworms with which students may be familiar). Schiro explains how he uses them to decompose organic matter, such as food and plant waste, and transform it into compost. His “underground farmers” at Growing Power work for peanuts, literally, and produce compost that is used to enrich soil, protect plants against drought, and grow food and flowers.
 
Activity Materials
Banana peels – one per student or group of students
Empty soda cans – one per student or group of students
Two-liter clear plastic soda bottles, with labels removed - one per student or group of students)
Scissors, enough pairs for students to share
Plastic Wrap
Organic materials (such as raw vegetables, fruits and fruit peels, or eggshells. Do not use cooked vegetables or fruits, or meat or dairy products)
Plastic spoons – one per student or group of students
Rubber bands – one per student or group of students
Package of potting soil, available at a garden supply store or florist
Small cups of water, enough for students to share
Paper plates – one per student or group of students
Clean sheets of paper – one per student or group of students
 
Vocabulary
Compost: mixture of decomposed plant and other organic matter.
Decomposition: breakdown of organic material.
Inorganic: material, usually non-living, that is not easily decomposed.
Organic: material, usually living, that is easily decomposed.
Squirm: a group of worms
Microorganisms: any organism that is too small to see with the unaided eye -- such as a bacterium.
 
What To Do

1. Before the lesson, make copies of the “Compost Column Data Sheet” , one for each student or group of students. Click here to download pdf of data sheet.

2. Begin the lesson by having students watch the Science Friday video, “Worms at Work.” Discuss with students how Steve Schiro cares for his squirm of worms. Tell students that they are going to learn about the process of decomposition and build a compost column.

Activity One: Decomposition

1. On a clean sheet of paper, have students create a chart with two columns, one labeled “Predictions” and the other labeled “Observations,” and two rows, one labeled “Banana” and the other labeled “Soda Can.”

2. Hand out a banana, soda can and paper plate to each student. Have students peel the banana and place the peel on the paper plate. Ask students to describe how the banana peel looks now. How will the banana peel look tomorrow or the next day? Have students write their predictions on their chart.

3. Have students make the same predictions about the soda can. What will the soda can look like tomorrow or the next day? Have students write their predictions on their chart. Have students place both the soda can and banana peel in a safe, dry place, such as a cupboard.

4. Over the next three days, have students observe once a day the appearances of the banana peel and soda can, and write their observations next to their predictions.

5. On the third day, ask students to describe what they think is happening to the banana peel. Why did the appearance of the banana peel change but not the appearance of the soda can? What are some differences in the material of the banana peel and the soda can?

6. Ask students to name things that they think are organic, and things that they think are inorganic. After taking suggestions, tell students that things that are organic can decompose, while some things that are inorganic take a longer time to decompose or may not decompose at all. Is the banana peel organic or inorganic? What about the soda can?

7. Ask the students to think about how the decomposition of the banana peel relates to the red wiggler worms that Steve Schiro has at Growing Power. After taking suggestions, tell students that invisible microorganisms, such as bacteria, help break down the banana peel in the cupboard, similar to the way that worms help break down organic matter.

Activity Two: Compost Columns

1. Tell students that they are going to build a compost column of soil and shredded organic material so that they can observe the decomposition process over the course of three to five weeks.

2. Have students use scissors to carefully cut off the top of the soda bottle so that they are left with a column shape. Discard the top for recycling.

3. Have students place a thin layer of soil at the bottom of the soda bottle and then add a thin layer of shredded organic material (such as a combination of lettuce, raked leaves, strips of newspaper). Use a plastic spoon to add one spoonful of water. Make sure the mixture is moist, but not soaked or muddy. Ask the students why they think water is an important ingredient in this “recipe.”

4. Continue adding layers of soil, organic material and water until the column is about an inch from the top of the plastic bottle. Add one last layer of soil and then cover the top of the column with a piece of plastic wrap. Secure with a rubber band.

5. On a second clean sheet of paper, have students create a chart entitled “Compost Column Data Sheet. Have student make two columns, one labeled “Predictions” and the other labeled “Observations,” and rows for data, such as room temperature, odor, texture, moisture, amount of light, and any other observations they can make. Have students place each compost column in a different location, where the column will spend the next two to three weeks.

6. During the next two to three weeks, each compost column’s contents will need to be aerated once a week by stirring with a plastic spoon. Ask students why aeration is important. If the compost dries out, add some more water. The compost’s moisture level should be similar to a damp sponge.

7. After two to three weeks, have students compare and contrast their results. Do all the compost columns look the same? What happened to the organic matter that was placed inside the compost?

Note: Once a column’s mixture has become dark and crumbly, students can plant a seed or seedling in the compost column, or use it to nourish plants, indoors or outdoors. The contents will be rich in nutrients and ready to use for planting.

What’s Happening?
Composting is the management and acceleration of decomposition to produce a nutrient-rich mixture that has numerous uses. It is an efficient means of recycling organic material from the kitchen or garden, and is ideal for gardeners who want to retain moisture, increase organic content, and improve aeration of soil. Compost can be used on potted plants indoors, too. There are a variety of ways to compost, from outdoor compost piles and bins to indoor worm bins.
 
Decomposition is the breakdown or recycling of organic matter into smaller components that can be used by other organisms. Decomposers are important organisms that decompose the remaining waste of other organisms, dead organic matter, and some inorganic matter.
 
The smallest--but most important--decomposers are the microscopic bacteria and fungi. Other larger decomposers include lichen, mosses, worms and wood eating insects such as termites, beetles, and certain ants. Insects and their larvae bore through decomposing matter creating tunnels and spaces, which aerates the compost, allowing the bacteria and fungi deeper access within the material. Decomposing matter also can provide homes and food for many organisms.
 
Many factors contribute to the processes of decomposition, including temperature, amount of light, aeration, moisture, type of material that is decomposing, and the source of bacteria and fungi. Generally, higher moisture and higher temperature can accelerate the rate of decomposition.
 
Topics for Science Class Discussion
  •  Would covering the banana peel with plastic wrap affect its rate of decomposition? Why/why not?
  •  Why does Steve Schiro not have to spend a lot of time aerating his compost?
  •  How can we set up an experiment to determine how quickly different organic materials take to decompose?
  •  Why can’t we use cooked vegetables or fruits, or meat or dairy products in compost? Could we use seaweed, fish bones or oyster shells?
  •  How long does it take for some inorganic materials to decompose? Have students do research and create a chart.
Extended Activities and Links
Repeat the second activity using different types of organic material in a couple of composting columns. Observe the new set of columns for three to five weeks and compare the results.
 
Have students observe the differences between a plant growing in regular soil, and a plant growing in a compost mixture. Students can make daily observations, take photographs of the plants and record their results on a data sheet. Do the seeds germinate faster in the compost or in regular soil? Does the compost affect the rate of growth or the size of the plant?
 
If you have access to woodlands, take students on a walk to observe fungi at work decomposing fallen branches and trees.
 
Visit the Growing Power website for Growing Power to learn more about how they use red wiggler worms to compost organic material:
http://www.growingpower.org/index.htm
 
Learn how to start a worm compost bin in the classroom:
http://earth911.com/news/2007/04/02/composting-with-worms/

Encourage students to bring in organic material to feed the worms.
 
Note: Once settled in a worm bin, red wigglers may start eating slowly. But after two to three weeks, they can consume as much as a gallon of organic scraps per week.
 

 

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