Understanding Soil Health in Simple Terms

What Healthy Soil Actually Is

Pick up a handful of soil from a good bit of old pasture and you will see it: dark, crumbly, sweet-smelling, alive with worms. That crumb structure is the whole game. A healthy soil is roughly half mineral particles, with the remaining space split between air, water and organic matter. It is that air and water balance that lets roots breathe and drink at the same time.

Inside a single teaspoon of decent soil there are more bacteria than there are people on the planet, plus fungal threads that stretch out and fetch water and nutrients for your plants. Worms are the visible workforce, dragging leaves underground and leaving castings behind. If your soil is teeming, you barely need to feed your plants at all. If it is dead and dusty, no amount of bagged fertiliser will fix it properly.

Test Before You Dig

Two cheap tests will tell you most of what you need to know before you start improving anything.

• pH. A simple probe or a liquid test kit from any garden centre will do. Most vegetables and most fruit want somewhere between 6.0 and 7.0. Brassicas do best nearer 6.5 to 7.5, which also helps against clubroot. Blueberries, rhododendrons and heathers want acid ground, below 5.5. If you are on chalk or limestone you will be alkaline and will need to add plenty of compost; if you are on peaty ground you will be acid and may need a little lime on the vegetable bed.
• Texture. Half-fill a jam jar with soil, top up with water, shake hard and leave it overnight. Sand settles first, then silt, then clay on top. The proportions tell you what you are farming: sandy ground drains fast and dries out, clay holds water and bakes hard in summer, and loam sits happily in the middle.

While you are at it, squeeze a ball of moist soil in your fist. If it holds together and ribbons between your fingers, you have plenty of clay. If it crumbles straight away, it is sandy. Neither is a disaster — both can be improved, just differently.

Add Organic Matter, and Keep Adding It

Organic matter is the single best thing you can give your soil. It feeds the worms and microbes, holds water in sandy ground, opens up heavy clay into crumbs, and slowly releases nutrients. Well-rotted farmyard manure, garden compost, leafmould and mushroom compost all do the job.

• Spread a good two to three inches over the surface in autumn and let the worms pull it down. No digging required.
• Never dig in fresh manure — let it rot down first, or it will burn roots and rob nitrogen as it breaks down.
• Mulch around established plants in spring with compost or leafmould to keep moisture in and weeds down.
• On heavy clay, add grit alongside organic matter for drainage, but be generous with the compost — clay needs it more than anything.

The old saying about feeding the soil rather than the plant is true. Do that for three or four years and you will notice the difference in the fork as much as in the crops.

Keep Off Wet Ground

Compaction is the quiet killer of smallholding soil. Every time you walk on sodden ground you squeeze the air out of it, and it can take years to recover. Clay soils are worst — tread on them in February and you will still see the damage next autumn.

Practical ways round it:

• Lay planks or scaffolding boards along beds to spread your weight when the ground is wet.
• Keep beds narrow enough that you never need to step on them.
• Avoid rotavating or digging clay when it is wet — you will smear it into a solid pan rather than breaking it up.
• Use a broadfork or garden fork instead of a spade where you can, lifting rather than turning the soil.
• Feed animals on a movable pen or a hardstanding over winter, rather than letting them poach the same gateway all season.

If you can work the ground when it is just moist — crumbly, not sticky — you will get the best results by far.

Never Leave the Ground Bare

Bare soil washes away, bakes hard and loses nutrients. Nature never leaves it that way, and nor should you. Sow green manures between crops and over winter: field beans and grazing rye are hardy and cheap, crimson clover and phacelia are kinder to pollinators and easier to dig in come spring.

Where you cannot sow, mulch with compost, straw or well-rotted woodchip. Even a rough tilth left over winter with the stubble still standing is better than a clean, empty bed. On a slope, a cover crop is the difference between keeping your topsoil and watching it go down the lane in the first heavy rain.

Reading Your Soil Through the Year

You do not need a laboratory. Dig a spade's depth of soil in spring and again in autumn, and look closely.

• Count the worms. Ten or more in a spadeful is a good sign; two or three means the life is struggling.
• Pour on a cup of water. If it soaks in within a few seconds, drainage is fine. If it sits there, you have a pan or too much clay.
• Crumble a lump. Good soil breaks into rounded aggregates like cottage cheese, not into dust or solid clods.
• Smell it. Healthy soil smells earthy and sweet. Sour or sulphurous means it is waterlogged and short of air.

Write down what you find each year, alongside what grew well and what sulked. Over a few seasons you will build up a proper picture of your own patch, and your soil will reward you for it.