Digging in to Food Security: Soil Studies
What follows is a collection of lessons on soils that supported a larger inquiry-based project by 7th and 8th grade students on food security in the Waupaca area community. The project was designed to be implemented using the large community garden as a context for learning. This community garden is a showcase feature of the Chain Exploration Center, a 4K-8 school, and, through the efforts of students, teachers, families, and community volunteers, has grown, and donated, a staggering amount of fresh produce for local food pantries. Students of the Chain of Exploration Center were fortunate to work with the nutrient management specialist of the Land and Water Conservation Office of Waupaca County for soil sampling and analysis. This community member provided soil probes and the expertise in collection of samples. He also sent the samples on to the lab and assisted in the interpretation of the results.
Lesson 1 Soil Sampling
Learning Target: I can use sampling tools to collect soils.
https://www.youtube.com/watch?v=SwBZp_AXy0Y This video may be shown to students to provide them with instructions on how to take 10 soil core samples to mix as a composite sample to send to the UW Soil Lab.
- Each student: notebook and pencils
- soil probes
- bucket for mixing soil cores.
- self-sealing plastic bags and/or soil sample bags available from the UW-Extension Office
- markers to label sample bags
Lead through the safe handling of soil probes, using caution as edges are sharp. Instruct students to collect 10 representative soil core samples from various locations in the garden. Place all core samples in a bucket and mix thoroughly, breaking clumps apart, removing large rocks or organic matter. Place a sufficient amount of the soil in the sample bags to send to the lab. Mark the bags with the requested information. (Chain of Exploration Center students were fortunate to work with the nutrient management specialist of the Land and Water Conservation Office of Waupaca County in this experience.) Each student team should take a sample of the soil and place it in a bag with their names, location of sample, date.
Repeat this process for the lawn and the woods. Students will be comparing the soil tests and land use.
Lesson 2 Soil Texturing by Feel
Learning Target: I can observe the characteristics of soil and identify the texture by feel.
- University of Wisconsin-Madison Arboretum. Earth Partnership for Schools. “3-14. Soil Texture Feel Test. Vkdfd2pfS2t3ejA/view?usp=sharing&resourcekey=0-Kq1ZDLzh902ja7tjANhIdg
- Basic Soil Sampling for Wisconsin Agriculture (video, 4:41 minutes) https://www.youtube.com/watch?v=SwBZp_AXy0Y This video may be shown to students to provide them with instructions on how to take 10 soil core samples to mix as a composite sample to send to the UW Soil Lab.
- Soil Texture by Feel (video, 4:04 minutes) https://www.youtube.com/watch?v=GWZwbVJCNec This brief video shows students how to find soil texture by feel.
- Identifying Soil Texture by Feel Flow Chart (one per student or pairs of students)https://drive.google.com/file/d/1dL5NkffVf04xFfxpq4AGmTF3CLNNVMV2/view?usp=sharing
- Each student: notebook and pencils
- Water to moisten samples and for hand rinsing
Demonstrate for students how to find soil texture by feel. Assist students in using the flowchart to specifically identify the soils from each of their three samples. Students will return the soil samples to their sample bags after testing each. Students should record their findings in their science notebooks.
Lesson 3 Soil Profile in a Jar
Learning Target: I can use mathematical processes to identify soil types.
Is This An Effective Soil Test? (video, 2:16 minutes) https://www.youtube.com/watch?v=u0fPNEyAolA This video demonstrates how to conduct a jar test to determine soil texture.
soil samples collected from garden, lawn and school forest
dry erase marker
small clear jars with lids
access to water
soil Texture Calculator (interactive webtool) https://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/survey/?cid=nrcs142p2_054167
each student: notebook and pencils, Metric ruler
Lesson Summary: Lead students determining soil texture using the jar method. Show the video to demonstrate. Any sand in the sample will settle quickly to the bottom of the jar. Students may also see silt particles settling next. Any clay in the sample will remain suspended for several hours. Instruct students to place the jars in a location where it will remain undisturbed until the next day.
The next day, students will observe the soil layers and will mark the top of each layer on the glass jar. Students will measure and record the height of all soil layers combined. This will be the denominator in the ratio. Calculate the proportion of each layer present in the sample.
Students will measure the depth of each layer. These measurements will be the numerators when calculating the portion of each soil layer.
Determine the proportion of each layer. Change this proportion to a percentage. Manually, find where the percentage of each component intersects in the soil triangle. Check this method by entering the percent of Sand, Silt, and Clay into the interactive tool: https://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/survey/?cid=nrcs142p2_054167
Record the soil type that has been identified.
Facilitate a discussion: How did the results of this test compare with the results of the texture by feel? Which method did you prefer? Why? Are there advantages of one over another?
Lesson 4 Chemical Properties of Soil Samples
Learning Target: I can use lab materials and procedures to determine the chemical properties of soil.
- distilled water
- safety glasses
- vinyl gloves
- filter paper
- Hach Soil Test Kit for Nitrogen, Phosphorus, Potassium https://support.hach.com/ci/okcsFattach/get/1014245_4
- Fertilizer Basics: A Tutorial (online article) https://wisconsinpollinators.com/Garden/G_FertilizerBasics.aspx
Guide students in drying and preparing soil samples.
Guide students in creating the soil extracts for testing.
Save remaining soil samples in case the testing must be repeated.
Conduct tests and record results.
Compile all data as a class. Discuss any data outliers and reasons why this may have occurred. Determine whether outliers should be averaged with the other terms, or they should be excluded Determine the need for any tests to be repeated.
Compare class data and analysis with that of the State Soil Lab. Talk with a county nutrient management specialist. Are soil amendments needed and a plan for doing so. What would soil amendments mean for food security?
Lesson 5 How Does Soil Work as a Filter?
Learning Target: I can describe why soil is sometimes a filter and sometimes it is a sieve.
“Soil Filter.” Dr. Dirt (online) https://www.doctordirt.org/teachingresources/soilfilter This resource is used for the lesson instructions.
- 3 oz and 5 oz solo cups (Put 3-5 holes in bottom of the 5 oz cup. A toothpick works well.). The 5 oz cup fits inside the 3 oz cup, then put the toothpick inside, between the cups.
- play sand
- fine soil
- grape Kool-aid
- Kool-aid in other colors, e.g., green, red, orange, yellow food coloring
- 2 inflated balloons
Open with a discussion of how water moves through soil and how nutrients may move with the water into plants as students have learned through our soil analysis and plant needs study. Also discuss that water in the soil may continue to move into the groundwater–our wells–and into surface waters. Discuss what happens when liquids–water-based or other chemicals– are applied to soils. Encourage students to think about the outcomes.
Tell students that the lab they are doing today will investigate some of these ideas.
Follow the setup and plan as written in the “Soil Filter” investigation linked above. After students conduct the “Floaties” portion of the investigation, they should observe that soil particles are too small to allow many materials to move through them with water.
Conduct the second part of the experiment in which the colored solutions are made with Kool Aid of various colors. Note that we cannot see the Kool Aid mix particles as they have dissolved. Students will investigate what comes out of the soil when these colored drink mixes move through the soils. They will find that some colors remain trapped in the soil–even though the the particles are small enough to move through the soil.
Lead a demonstration of two statically charged balloons. What things do the balloons pick up (oppositely charged materials)? What is repelled (same charge). Clay soils also have charged particles. The purple drink mix is made with red and blue dyed particles. Discuss which particles were attracted to the soil–what does this mean for their static electrical charge? What about the colored particles that passed through the soil? How could knowing this information about soil particles and electric charges help us in keeping our groundwater and surface waters clean? What does this mean for soils as they accumulate pollution particles?