The Jar Test — Know Your Soil Texture
Soil texture — the proportion of sand, silt, and clay — determines how your soil holds water, drains, and supports root growth. The jar test is a free, simple way to measure it.
What Texture Tells You
| High in... | Characteristics | Amendments |
|---|---|---|
| Sand | Drains fast, dries out, low nutrients | Add compost and clay for retention |
| Silt | Holds water well, can compact | Add compost for structure |
| Clay | Holds water and nutrients, drains slowly | Add gypsum and compost for drainage |
| Loam (balanced) | The ideal — good drainage AND retention | Maintain with compost and mulch |
Following the Method
The "Soil Biology Assessment — Jar Test" method on Libre Grow walks you through the test step by step. The key steps:
- Collect a composite soil sample from your bed (5+ spots, 10-15cm deep)
- Fill a jar one-third with soil, add a drop of detergent, fill with water
- Shake vigorously for 2-3 minutes
- Let settle: 1 minute = sand layer, 2 hours = silt layer, 24-48 hours = clay layer
- Measure each layer and calculate percentages
Recording Your Results
When you create the activity and select the "Jar Test" method, you'll see observation templates for:
- Sand percentage (numeric, %)
- Silt percentage (numeric, %)
- Clay percentage (numeric, %)
- Organic matter (scale: None → Abundant)
- Soil type (text — use a soil texture triangle to determine)
Record these for each bed. Next season, repeat the test in the same beds and compare.
The Soil Texture Triangle
Look up "soil texture triangle" online. Find where your percentages intersect — that's your soil type (sandy loam, silty clay, etc.). Record this in the "Soil type" observation field. Knowing your soil type helps you choose appropriate plants, amendments, and watering strategies.
Put It Into Practice
Collect soil from one of your beds and do the jar test. Record your results — what proportions of sand, silt, and clay did you find?