This lesson has been adapted from the lesson, "Eco-Enrichers", created by the National Park Service.
NOTE: Before starting this lesson, you will need to find and collect enough soil to fill three containers, each approximately 1 ft x 1 ft x 1 ft. You can use the same soil to fill 5-6 small cups for the beginning of the lesson, or you can collect enough to provide separate soil samples for each part of the lesson. While the soil samples should not be particularly rich (it might be heavily compacted, or might have been exposed to high levels of erosion, such as soil found on a roadside), they should still contain a mix of both organic and inorganic matter. Later on, you will also be needing worms. There are many choices for obtaining worms. The obvious one is to get them out of your own compost. Otherwise, they can be purchased (at certain times of the year) from bait stores (make sure you specify earthworms!) and ordered online. Now that more and more people are doing vermiculture, there are lots of online choices.
I start the lesson by providing each student table group a small styrofoam cup full of soil. I give the students a few minutes to manipulate and investigate the soil, making observations using their basic senses of tough, sight, and smell. I have them record their observations in their science journals,encouraging them to be as specific as possible. For example, rather than writing, "The soil is wet," I ask them to write a more descriptive sentence such as, "There is no visible water, but soil is slightly damp and cool to the touch."
*Writing descriptive observations may be easier for some students than others, so I find that I usually have to circulate the room, pointing out some of the more accurate and descriptive observations to the class as models, and also prompting and helping some students to write with more detail. I explain that want them to remember exactly what they observed when they read it again in a few days.
Once the students have collected qualitative data, I have them investigate a little further into the quantitative attributes of the soil. I lead them through a series of mini-investigations, such as examining a sample under a microscope and counting the number of organisms in the sample, estimating the number of organisms in the entire quantity (based on their earlier count under the microscope), measuring the pH, nitrogen, phosphorus, and potassium levels using a soil test kit, testing the porosity by determining how fast water will run through, and/or conducting a soil texture test to see what components are present and in what proportions (ex: sand, silt, clay, organic matter).
After the soil tests have been completed and recorded, I collect the cups of soil and have three student assistants redistribute it into the three 1x1x1 containers. While this is going on, I prompt the class to pay attention to the video clip (below).
After watching the video, I ask if any of the students have every tried composting, or have ever planted or tended to a garden. I ask those who respond to share their experiences. Next, I ask my student who have gardened to explain why fertilizer is so important to their plants. This not only activates background knowledge, but provides relevance to the lesson for many of the students.
Next, I pose the following questions to the whole class:
"You have just learned about how composting can produce a fertilizer which helps plants and trees to grow. Do you think humans can do anything to speed up or improve this process? Do you think animals can do anything to speed up or improve this process?
I give the students 1-2 minutes of think time, then direct them to write their responses on the "Hypothesis" section of their recording sheet.
As a homework assignment, I ask the student to brainstorm some ways we could test our hypotheses in class and to bring their ideas to class the next day.
Once an experiment and procedures have been created and written down, I make a copy for each student. This will serve as a lab guide of sorts. We decide who will be responsible for completing daily observations, manipulation of the variables, and testing the soil, and post this on a schedulein the classroom, as well as in the students' science journals, in order to make sure everyone is aware of the procedures and the expectations.
At the end of each week and at the conclusion of the three-week period, we conduct the same set of tests that we originally conducted with the soil on day 1. The students record their results in their science journals. At the end of our experiment, they will graph their results to see how the attributes of the soil had changed over the three week time frame.
Once we have collected and graphed our data, it is time to discuss the findings. We have a class discussion, identifying and analyzing the differences in the three soil samples. I have the students each research one of the soils attributes to learn about the ideal environment to foster plant growth. We will use our class data and the student research to determine which soil sample is optimal for plant growth. Students will then form their conclusions, comparing them to their original hypothesis.
In order to see if the students' conclusions were correct, I have them plant some seeds in all three of the soil boxes. (For this experiment, it is best to pick fast-growing seeds,such as radishes or lima beans.) I explain to the students how important it is to plant the same number of seeds in each of the soil boxes, to record the date of planting, all watering procedures and changes in the boxes as the plants begin to grow. After another three weeks, we compare and discuss the results.
Students will respond to four extended response questions using VoiceThread, a web platform used to communicate and collaborate through the use of multimedia. The questions increase in rigor as students progress through them. Students can respond by typing, using their phone or computer to record their voice, or by using their webcam to record a video comment. Once they respond to each question, they must also comment on the thoughts of at least two classmates' responses.