Growers Lab: The Percolation Test, Measuring How Your Soil Drinks
Junior Naturalist • Growers Grades 4–6 • Soil STEAM Lab
Growers Lab: Measuring How Your Soil Drinks (Grades 4–6)
How quickly does water move through soil, and why does that matter in the real world? In this upper-elementary soil lab, students conduct a percolation test to measure how fast water moves through different soil samples, compare data across trials, and design ways to reduce runoff. This version takes the same big idea from the Sprouts and Seedlings activities and turns it into a true investigation with timing, averages, graphing, evidence-based explanations, and simple environmental engineering.
This is where children begin to move from noticing patterns to explaining them. Instead of just saying that one soil “drank faster,” students are asked to measure, compare, and defend their thinking with evidence. They can connect their findings to puddles on playgrounds, compacted paths, healthy garden beds, erosion, and stormwater problems in their own communities.
Soil STEAM Pathways
This post is the third step in the same soil learning progression.
Quick Look
- Time: 45–60 minutes
- Prep: 10–15 minutes
- Mess Level: Medium
- Group Size: Pairs or small groups
- Best Setting: Outdoor table, tray setup, or science station with easy cleanup
Learning Goals
- Compare how quickly different soils absorb water
- Collect timed data across multiple trials
- Calculate or compare averages
- Represent results with a chart or bar graph
- Explain how particle arrangement, pore space, compaction, and organic matter affect water movement
- Propose an engineering solution to reduce runoff
Materials
- Clear jars, cups, or cut bottles with matching size
- 3 soil types, such as sand, garden soil, and compacted soil
- Water, measured equally for each trial
- Timer or stopwatch
- Ruler
- Notebook or printable data sheet
- Optional: funnel, tray, graph paper, digital scale, and compost sample
Why This Investigation Matters
Older elementary students are ready to notice that soil is not just “dirt.” It is a system made of particles, pore spaces, water, air, roots, and organic matter. When those parts are arranged differently, water behaves differently too.
That makes this an especially powerful lesson for students who are beginning to think like scientists and designers. They are not just observing a change. They are measuring a process, finding a pattern, and using what they learned to suggest better solutions for real spaces like gardens, trails, parks, and schoolyards.
Procedure
Engage: Ask, “If the same rain falls on loose soil and packed soil, where does the water go?” Have students record a prediction before they begin.
Explore:
- Fill each container with the same depth of soil, about 8–10 cm.
- Use the same amount of water for each test.
- Pour the water into one sample and start the timer.
- Record how long it takes for visible surface water to disappear.
- Repeat for at least 3 trials with each soil type.
Explain:
- Compare results across the different samples.
- Discuss pore space, compaction, and infiltration.
- Introduce the term percolation as water moving downward through soil.
- Have students calculate an average or identify patterns across trials.
Elaborate: Ask students how a schoolyard, sidewalk edge, or garden could be changed to reduce runoff and improve water absorption.
- Add compost or other organic matter
- Add mulch to protect the surface
- Plant roots or groundcover to stabilize soil
- Create a shallow rain garden basin
- Reduce repeated compaction from foot traffic
Evaluate:
- Completed data sheet
- Bar graph or comparison chart
- Short CER response: Claim, Evidence, Reasoning
- Engineering proposal or redesign sketch
- “Which soil percolated fastest, and what evidence supports that?”
- “How did compaction change the result?”
- “What role might pore space play?”
- “How could organic matter change what happened?”
- “If this were a real playground or garden, what would you improve?”
What the Data Can Show
Students often discover that not all soil samples behave the same, even when they all receive the same amount of water. A compacted sample may keep water on the surface longer, while a looser or more structured sample may allow water to move down more quickly. These patterns help students see why some places flood, puddle, or erode more easily than others.
This is also a strong place to talk about fair tests. If students want reliable results, they need to keep key variables as consistent as possible: same container size, same soil depth, same water amount, and similar timing. That turns a messy activity into real experimental thinking.
Standards Alignment
- NGSS 4-ESS2-1: Students make observations and measurements that provide evidence about erosion and the effects of water on land surfaces.
- NGSS 5-ESS2-1: Students connect soil and water interactions to larger Earth systems.
- NGSS 3-5-ETS1-2: Students generate and compare possible solutions to reduce runoff or improve infiltration.
- CCSS Math: Students represent and interpret data using tables, measurements, averages, and graphs.
- CCSS ELA: Students write explanatory responses using evidence from their investigation.
- Minnesota Science Practices: Students observe, analyze data, and design solutions to explain natural and human-made systems.
Connecting to Real Soil Systems
Healthy soil is a living, functional system, not just a planting medium. When students test percolation, they are really studying how a soil system regulates water. That connects directly to rain gardens, erosion prevention, compost, native roots, soil food webs, and the design of resilient landscapes.
This is a great point in the series to help students think beyond the cup or jar. The same question applies outdoors: how does water move through the ground where we live, and what can people do to help that system work better?
- Understanding Soil Food Webs: Healthy Soil Organisms
- How Deep-Rooted Native Plants Prevent Erosion
- Explore All Soil Health Resources
Extend Online
Students can compare results, revisit the soil sequence, and explore interactive extensions here:
🌧 Online Interactive Soil STEAM Extensions
Download the Full Soil Science Lesson Plan
Want the complete standards-aligned teacher version with printable data sheets, differentiation support, and assessment tools for the full multi-age soil sequence?
Subscribers receive the soil science lesson plan adapted for multiple age groups, plus future Junior Naturalist activities and updates.
Teacher Quick Links
Frequently Asked Questions
Why does compacted soil increase flooding or runoff?
Compacted soil usually has fewer large pore spaces, so water moves through it less easily and more of it may stay on the surface.
How does organic matter help soil absorb water?
Organic matter supports better soil structure, helps keep particles from packing too tightly, and can improve infiltration over time.
What is the difference between infiltration and percolation?
Infiltration is water entering the soil surface. Percolation is the movement of that water downward through the soil.
What makes this a good upper-elementary lab?
Students are combining observation, measurement, graphing, explanation, and design thinking in one investigation. That makes it a strong bridge between hands-on science and environmental problem solving.
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