Urban Soil Health for Community Gardens
Soil ecology and amendment planning for a real Detroit urban farm plot.
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Standards
HS-LS2-7 — Design, evaluate, and refine a solution for reducing the impacts of human activities on the environment and biodiversity.
Why Does This Matter?
Detroit has one of the largest urban agriculture movements in the country, with thousands of community gardens and farms built on formerly vacant lots. Good soil is the foundation of every one of them — and decades of vacancy often leaves soil compacted and low in organic matter.
Objective
Test key properties of a soil sample and design an evidence-based amendment plan suitable for a Detroit urban farm plot.
Materials
- Soil sample (from schoolyard, a garden plot, or teacher-provided)
- Soil pH test kit or strips
- Clear jar with lid (for soil texture/settling test)
- Water
- Ruler
Safety: Wash hands after handling soil. Do not taste or ingest samples.
Procedure
- Fill a clear jar about one-third with your soil sample, then fill the rest with water. Seal and shake well.
- Let the jar settle undisturbed for at least 24 hours. Sand settles first (bottom), then silt, then clay (top layer), with organic matter often floating.
- Measure the thickness of each settled layer with a ruler and calculate the approximate percentage of sand, silt, and clay.
- Test a separate soil sample's pH using your test kit, following kit instructions.
- Observe the sample for visible organic matter (roots, decomposing leaves, worms) and record a qualitative organic matter rating (low/medium/high).
- Using your results, design an amendment plan (e.g. compost, cover crops, lime, or sulfur) to improve the soil for vegetable growing.
Data Table
| Measurement | Result | Ideal range for vegetable garden |
|---|---|---|
| Sand layer thickness / % | ~40% | |
| Silt layer thickness / % | ~40% | |
| Clay layer thickness / % | ~20% | |
| Soil pH | 6.0–7.0 | |
| Organic matter (low/med/high) | Medium–high |
Analysis Questions
- Based on your texture test, would you classify your sample as sandy, clay-heavy, or well-balanced (loam)? What does that mean for water drainage and root growth?
- Was your soil's pH within the ideal range for vegetables? If not, what amendment would raise or lower it?
- Why might soil on a formerly vacant Detroit lot have low organic matter compared to a long-tended farm field?
- Write a one-paragraph amendment plan for your sample, citing your specific data to justify each recommendation.