Before you can heal the soil, you must know it. Before you can cook for it, you must understand what kind of kitchen you are standing in.
Most growers begin in the middle — adding inputs to soil they have never properly diagnosed. It is the equivalent of writing a prescription before taking a history. The three tests in Part I cost almost nothing, require no laboratory, and take less than twenty-four hours of your attention. They will tell you more about what your soil actually needs than a season of guesswork. They are not preliminary exercises to get through. They are the practice itself.
What the jar test teaches you: the texture of your soil — sand, silt, clay, and organic matter — and therefore its drainage, its nutrient-holding capacity, its workability, and its fundamental character.
Why this matters before you do anything else: A soil that is 80% sand needs a completely different set of interventions from a soil that is 50% clay. Feeding a sandy soil like a clay soil is a waste of money and effort. Feeding a clay soil like a sandy soil will drown it. The jar test ends the guessing.
A clear glass jar with a tight lid (a 1-litre mason jar is ideal)
A soil sample from 10–15 cm below the surface (past the mulch, into the root zone)
Chlorine-free water (let tap water sit uncovered overnight, or use rainwater)
A ruler, a marker, and a piece of tape
24 hours of undisturbed patience
Dig past the surface debris. You want the mineral soil from the root zone. Remove large roots, stones, and obvious organic matter.
Fill the jar one-third full with your sample.
Fill to within 2 cm of the top with chlorine-free water.
Seal the lid and shake hard for two full minutes. You are breaking apart soil aggregates, suspending every particle.
Set the jar on a completely flat, completely undisturbed surface. Note the time. Walk away.
Within the first minute, the sand falls — heavy, gritty, at the bottom. After 2–3 hours, the silt settles above it. After 24 hours, the clay arrives at the top of the mineral column. Floating at the surface, or suspended just above the clay, is the organic matter — the decomposed record of biological life.
Measure each layer. Divide each layer's height by the total height of all settled mineral layers (not including floating organics) and multiply by 100. This gives you percentages.
Field note: The jar test is useful not because it gives a laboratory reading, but because it slows the practitioner down. When the soil settles in layers, you begin to see that a bed has a memory. Sand, silt, clay, organic matter, and disturbance all leave their signature. Run this test on several spots across your growing area. You will likely get different stories from plots just a few metres apart. The jar does not just tell you what the soil is. It tells you what has been done to it.