The short version
Soil does three jobs: it holds water, it holds air, and it holds nutrition. Most disappointing crops come from soil failing one of those, not from the plant. Knowing which kind you have tells you what to do and, just as usefully, what not to bother with.
What you need
A trowel and a jam jar
Enough to find out what you have. The jar test settles the texture question in a day.
A pH test
Cheap, and worth doing once. pH decides which nutrients a plant can actually take up, however much of them are present.
How to do it
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Squeeze a handful
Sandy soil falls apart. Clay rolls into a sausage and shines when smoothed. Loam holds together and crumbles when pushed.
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Do the jar test
Half fill a jar with soil, top up with water, shake and leave a day. Sand settles first, then silt, then clay on top. The bands give you the proportions.
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Test the pH
Most vegetables want 6.0 to 7.0. Below 5.5 or above 7.5, nutrients lock up even in rich soil.
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Dig a hole and fill it with water
If it has not drained in four hours, drainage is your limiting factor and nothing else you do will matter as much.
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Add organic matter, whatever the answer was
Compost improves every soil type: it opens clay and it gives sand something to hold water with. It is the one universal answer.
When it goes wrong
Puddles that sit for hours
- Drainage
- Compaction
Compaction or heavy clay. Raised beds are the quickest fix; compost is the slow one.
Soil dries out within a day
- Sand
- Organic matter
Sandy soil with little organic matter. Mulch and compost, repeatedly. There is no single-season fix.
Yellow leaves in rich soil
- pH
Nutrients are present but locked up by pH. Test before feeding: more fertiliser will not help.
Frequently asked questions
Should I dig every year?
Not necessarily. Digging turns weed seed up and breaks the soil structure. Mulching the surface and letting worms work it in does the same job with less damage.
How much compost is enough?
A 5 cm (2 in) layer over the surface each year is a good working amount. More does no harm on poor soil.
Can I change my soil type?
Not the texture, no. You can change the structure and the fertility, and those are what actually limit growth.
