The useful layer is thinner than the spade that digs it

A vertical strip of ground, split open from collar to hem. Leaf litter first, then a dark crumbling band, then something paler and denser, then broken rock at the hem. A spade blade is cut into the left edge, driven in only as far as a spade actually goes, and against it every layer carries a single letter: O, A, B, C.

The blade is the whole argument. Everything that matters is shallower than it is.

What is this diagram actually a cross-section of?

A soil profile — the layers, or horizons, that stack up under any patch of ground that's been left alone long enough to sort itself out.

O is the loose organic litter on top, not yet broken down into anything else. A is topsoil proper, the dark crumbling band where roots, worms and years of dead leaves have mixed themselves into something a plant can use. B is subsoil, paler and denser, mineral rather than organic. C is broken parent rock, the material everything above it was made from. The letters are the standard naming used across soil science, not an invention for this shirt.

Why does the top band matter so much more than the ones below it?

Because it's the only one a plant's fine roots can actually work, and in most gardens it's a strikingly thin band to be doing all that work in.

The A horizon is where nutrients, air and water are available together; below it, roots thin out and progress slows. A garden that's producing well is almost always living entirely within a depth a spade can turn over in one go — a smaller volume than most people picture when they talk about "the soil", and roughly the same depth a hoe with a near-flat blade is built to skim rather than dig into.

Why is the spade drawn in for scale rather than a ruler or a dimension line?

Because a ruler describes the ground; a spade describes what a gardener actually has to work it with.

Cut into the edge of the section at the depth it's actually driven to, the blade turns an abstract stack of colours into a comparison a reader can check against their own tool shed: whatever the spade covers is the part in play, whatever it doesn't reach might as well be a different country. Figures on a diagram get skimmed past. A familiar object at true scale doesn't.

Who owns a diagram of soil horizons?

Nobody. Horizon letters and the layered structure they describe are how soil scientists talk about any ground, not a design any one person or company holds.

What's owned is a specific site's own survey data, a lab's branded soil-testing report, or a nursery's own compost blend — licensable the ordinary way if a real one is the point of the shirt. Left generic, a soil profile stays a plain description of how ground is built, which needs nobody's permission.

Does this only make sense for a garden with lawns and borders?

No — the same profile sits under an allotment, a farmer's field or a builder's foundation trench, because the layering is a property of undisturbed ground generally, not of ornamental planting.

What changes between them is only how deep the working band needs to be. A vegetable bed lives in the A horizon; a tree's roots reach into B; a footing goes through all of it into C. It's the same section every time, in the way that a heap sorts itself into graded bands purely by standing still long enough — only the question being asked of it changes.

Isn't a few centimetres of topsoil too small a thing to print this large?

That's rather the point of putting it at full height instead of as a small inset.

Blown up to fill a shirt from collar to hem, a thin band of topsoil stops looking incidental and starts looking like what it is: the entire working depth of a garden, drawn at a scale that makes its shallowness impossible to miss. A small diagram would let the reader assume there's more of it than there is — the same reason it's worth knowing where the cold pools on a plot, since a low corner can sit several degrees colder than the rest of the same small piece of ground.

Does it print well?

Yes — four flat horizontal bands with a hard-edged blade cut into one side are simple, sturdy shapes that survive fabric well.

Warm brown ground with the layers graded cream through dark grey keeps the bands distinct without needing more than two inks; the spade stays a flat cream silhouette rather than a shaded object, so it reads instantly against the section behind it. Keep the letters small and plain — they're a label, not the design.

How do I get one made?

Describe your ground at JustOG — how many layers to show, and how deep to cut the spade in. Pick a direction, drag the crop frame, see it composited on the real garment, and it's made to order and shipped.

Designs other people have published are in the shop.

Leaf litter at the collar, broken rock at the hem, and a spade that only ever reaches partway down.