Lesson Summary: The purpose of this lesson is for students to observe the effects of decomposition by soil microbes. A mini compost pile will be assembled in the classroom, where students can observe how food scraps decompose over time. This activity also explores other ways the presence of microbes can be detected.
Subject: Science, Gardening
Grade Level: 6th-8th
Time Required: Prep Time: 45 minutes
Decomposition Observation Time: 2-5 weeks
Materials:
· 5 Gallon Plastic Container
· Soil
· Drill
· Spray Bottle
· Stirring Utensil
· Piece of paper or a paper towel (2-4 weeks)
· Banana or orange peel (2-5 weeks)
DO COMPOST / DON'T COMPOST· All your vegetable and fruit wastes, (including rinds and cores) even if they are moldy and ugly
· Old bread, donuts, cookies, crackers, pizza crust, noodles: anything made out of flour!
· Grains (cooked or uncooked): rice, barley, you name it
· Coffee grounds, tea bags, filters
· Fruit or vegetable pulp from juicing
· Old spices
· Outdated boxed foods from the pantry
· Egg shells (crush well)
· Corn cobs and husks (cobs breakdown very slowly) / · Meat or meat waste, such as bones, fat, gristle, skin, etc.
· Fish or fish waste
· Dairy products, such as cheese, butter, cottage cheese, yogurt, cream cheese, sour cream, etc.
· Grease and oils of any kind
Why can't you compost these food wastes?
· They inbalance the otherwise nutrient-rich structure of other food and vegetation waste and breakdown slowly
· They attract rodents and other scavenging animals
· Meat attracts maggots
· Your compost bin will smell!
Activity Introduction/Preparation:
The PowerPoint, Soil Microbes and Their Role, may be shown to the students as an introduction to teach the different types of soil microbes and how they interact with the soil to help plants grow. Explain to the students that a compost bin is often built outside, and is used to recycle food to make fertilizer that can be used in gardens.
To assemble the compost bin:
1. Drill holes along the bottom and the sides of the container. Holes should be spaced about 4-6 inches apart.
2. Place the bin in an area of the classroom where it will receive sunlight but not experience temperature extremes.
2. Place the bin on a plate or the lid where excess moisture draining out can be caught.
3. Add a layer of potting soil to the bottom of the bin. Add dry leaves, and a few red earthworms or pillbugs if these are available.
4. Add a piece of paper, paper towel, banana peel, or orange peel to the compost.
Activity Plan:
· Explain to the students what compost bins are and how they are used to decompose food and other organic matter.
· Encourage students to bring food scraps such as fruits and vegetables and organic matter such as dry leaves. Students can also bring in earthworms and pill bugs. Meat, dairy products, and glossy paper are not good items to add to the compost bin.
· The compost bin needs to be misted daily and stirred once a week. Assign students to do these tasks.
· Lead the students in a discussion of what they think will happen to the organic matter in the compost bin.
· The paper will decompose in 2-4 weeks and the banana or orange peel will decompose in 2-5 weeks.
· When all of the material has been sufficiently decomposed, spread the compost outside in a flower bed. Make sure to get permission from the school administration first.
Assessment: Give the students the handout provided, were they can record their observations of the compost pile over a few weeks. The students will draw pictures to represent the decomposition of the food and touch and smell the compost. If you use laboratory notebooks in your classroom, have the student record their observations and write down the answers there.
Lesson Extensions:
· Perform an experiment to see how the presence of organic matter for soil microbes to decompose effects the growth of a plant. For the control variable, plant a plant in soil with no leaves, worms, pill bugs, or food added. Plant an identical plant in the compost pin. Observe the plant growth over a few weeks. What conclusions can be drawn about the role of soil microbes and how this affects plants?
· Place a cup of limewater in the covered compost bin or in a closed jar with a bit of soil in it. The limewater will turn a milky color in two or three days. Lime water turns milky in the presence of carbon dioxide. It can be inferred from this observation that there must be organisms in the soil consuming oxygen and producing carbon dioxide.
References: Here are some websites that may be helpful
http://cwmi.css.cornell.edu/compostingtoreduce.pdf
http://tlc.howstuffworks.com/family/science-projects-for-kids-soil-experiments5.htm
TEKS: Science-
6.1 (B) / 7.1 (B) / 8.1 (B) Practice appropriate use and conservation of resources, including disposal, reuse, or recycling of materials.
6.2 (C) / 7.2 (B) / 8.2 (B) Collect and record data using the International System of Units (SI) and qualitative means such as labeled drawings, writing, and graphic organizers.
6.3 (C) / 7.3 (C) / 8.3 (C) Identify advantages and limitations of models such as size, scale, properties, and materials.
7.5 (B) Demonstrate and explain the cycling of matter within living systems such as the decay of biomass in a compost bin.
7.6 (A) Identify that organic compounds contain carbon and other elements such as hydrogen, oxygen, phosphorus, nitrogen, and sulfur.
Authors:
Undergraduate Fellow: Megan Landon
Graduate Fellow: Jennifer Graham
A product of the Partnership for Environmental Education and Rural Health at Texas A&M University