Tuesday, September 3, 2013


The trash has been collected. The trash has been taken to the dump. The late summer rains have started. In other words, the stage has been set.
Now that you and your students have buried the trash into the decomp tub, the seeds of curiosity have been planted. Your students, and maybe even you, are anxious to discover what will become of the treasures hidden beneath the soil. Over the next few months, take advantage of that curiosity and build an educational unit around it. In the process, your students will learn about their environment, their impact on the environment, and how to become better stewards of our beautiful blue planet.

Today’s post contains the continuation of the decomposition project with the posting of Phase 2: After the Rain Falls. For the sake of continuity, every time a new phase is added to the project, the preceding phases will be included as well. Whenever an adjunct activity is added, a link to the phases will be posted through an image.

Link to previous post with all images.
Grade Range: K – 3
Time to complete: Preparation: varies, Activity: 60-75 minutes

Students will make predictions based on their prior knowledge about which items placed in a plastic tub will decompose.
Students will list and describe the conditions necessary for an object to decompose.
Students will gather and interpret data related to weather.
Students will read a grid map to locate and identify objects.
Students will identify and describe various types of soil based on appearance and physical properties.

Words to know: decompose, precipitation (rain, snow, sleet), weather, plastic, paper, metal, glass, measure

This project is designed as a cross-curriculum activity to address the environmental impact caused by the things we use for normal daily living. Students will conduct a year-long decomposition project, culminating with an excavation activity and seasonal planting, just in time for Earth Day in April. Additional, but optional, areas of study include weather patterns, regional climates, sorting materials, daily record keeping, identifying various forms of precipitation, grid and map reading skills, and implementing the scientific process.


Plastic tub with lid
Plastic tub the same size as the decomp tub (for activities conducted inside)
Wire snips
String or thin ribbon
Dry soil from the area
Enough gallon size zipper bags to allow one for each student
Various items to place into the tub of dirt of different materials (paper, cardboard, metal, plastic, cloth, glass, etc.)—i.e. trash
Rain gauge or plastic container (if project is conducted inside)
Plastic drop cloth for classroom (if project is conducted inside)
Camera (optional)

For demonstration purposes, the items placed in the decomp tub are geared towards a target audience of first to third grade students.

1. Prior to the activity, prepare the tub by cutting slots at regular intervals across the edges of the tub. These slots will be used to add the rope grid.
2. Using an awl or drill, add several small drain holes at the bottom of the tub. These will simulate natural drainage of many types of soil.
3. Involve the students in the preparation process:
a. Conduct a guided classroom discussion and collection of objects in your school that are made of various materials. Assign a homework project to bring in 2 small objects—one they predict will decompose and one object they predict will not.
b. Have each student bring in 2 cups of soil from their yard in a sealed plastic bag to place into the decomposition tub. Depending upon the size of tub used, you may need to supplement with soil from your yard. A follow-up activity based on this task will be added later in the year.

1. If the project is conducted inside, place the plastic drop cloth on the floor.
2. Sort the items that were brought in by the students by material. If an object is composed of more than one type of material, choose the prominent material for the category.
3. Select the items to be placed into the tub. This step is a great springboard for a discussion on size as not all of the objects will fit into the tub. The goal is to select a sampling of material types. (Plastic, paper, cardboard, metal, glass, Styrofoam, coated paper, etc.) Set the selected items to the side while step 4 is completed.

*It helps to cut some of the larger items to a smaller size to allow room for more objects.
4. Fill the tub half way with the soil that was collected by the students. Mix the soil well with hands or a small shovel.
5. Arrange the items on the layer of soil, avoiding overlaps.
6. Add the string or ribbon grid to the tub. This will be used to help locate the items near the end of the project in the spring. Take a photo of the tub with the objects. This photo will also be used for a follow-up activity later this month.
7. Carefully add the remaining soil to cover the objects. There should be at least 2 to 3 inches of soil over the objects.
8. Place the rain gauge outside and wait for the next rainfall. If possible, set the decomp tub outside where it will receive the full effects of weather changes (sun, rain, wind, etc.)

*If the decomp tub is going to remain in the classroom, find a suitable area where the students can see the tub but it will remain undisturbed. Placement close to a window is also a good idea. Place the lid under the tub to catch the water that drains from the holes in the tub.
9. Check this blog for the next segment of this year-long project.


Grade Range: K – 3
Time to complete: Preparation: varies, Activity: 15-20 minutes, completed on a regular basis
This phase is, in essence, the meat of the project. It will take several months to complete, which will allow for many opportunities to provide related activities throughout the year. The phase focuses on the process of decomposition and the criteria necessary for decomposition to take place. As differences in regional climates may affect the decomposition process in your area, please take note of modification suggestions.

MATERIALS (continued from Phase 1):
Watering can
Wall chart (see sample)

Hint 1: This activity is conducted in an east coast community with a climate that experiences an average of 3 to 5 inches of rain a month. Summers are hot and humid.  Autumn weather varies, but are typically wet and warm. Winters are cool with infrequent snowfall. In order for decomposition to take place, the trash must be placed in a location where there is heat and moisture. If one of these components is missing, then the results may vary. If you live in an area that is cooler and/or drier, you might find this a good opportunity to reach out to schools or homeschool co-ops in different regions to use as a comparison for results. You could even set up 2 decomp tubs and control the climate effects for a direct comparison. This project is great for sharing with other students!
Hint 2: This activity is best conducted outside. However, if this is not possible in your area modifications are provided.

1. As soon as your area receives rainfall, bring the rain gauge inside. Measure the amount of rainfall. Add a color coded strip of paper to the wall chart rain gauge. For younger students, it helps to increase the size of the color blocks by a factor of 3. Each inch of rainfall is represented by a 3 inch strip of paper.
 2. Mark the calendar each time there is rainfall in your area.

*If the decomp tub remains outside, skip steps 3 and 4.

3. If the decomp tub is kept inside, fill the extra tub with the water level to match the rainfall total for the day. Pour the water into the watering can.

4. Take turns slowly pouring the water over the soil in the tub, making sure to wet all areas of the soil.
5. Explain to the students that water is necessary for the trash they buried to decompose.

6. Repeat these steps every time there is precipitation in your area. Adjustments for snowfall will be added at a later date.
For now, focus on tracking the amount of rainfall, the dates of each rainfall, and the daily high temperatures. Check back frequently for additional activities to be posted.

Just as with the process of decomposition, this project takes time.

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