Types of Soil

Not all soils are the same. The soil in your back garden might be very different from the soil in the next street, the next county, or the next country. Soil scientists usually sort soils into six main types based on the mix of mineral particles in them: sand, silt, clay, loam, chalky and peat. The type matters because it controls how much water the soil holds, how easily plants can grow in it, and what kind of farming or gardening is possible.

  • Main types6Sand, silt, clay, loam, chalk, peat
  • Best for most plantsLoamBalanced mix of sand, silt and clay
  • Drains fastestSandBig particles, lots of air space
  • Drains slowestClayTiny particles pack tightly together
  • Most acidicPeatSoggy with old plant material
  • Most alkalineChalkyFull of calcium carbonate

The six main soil types

  • Sandy soil: feels gritty. Made of big particles (0.05 to 2 mm). Drains very fast, warms up quickly in spring, but does not hold many nutrients. Common at the coast and in deserts.
  • Silty soil: feels smooth and soapy when wet. Made of medium-sized particles. Holds water and nutrients well. Often found near rivers.
  • Clay soil: feels sticky when wet, hard as concrete when dry. Made of incredibly tiny particles. Holds nutrients well but drains very slowly.
  • Loamy soil: a balanced mix of sand, silt and clay (roughly 40/40/20%). Considered the best general soil for farming and gardening.
  • Chalky soil: pale, stony, contains lots of calcium carbonate. Alkaline (high pH). Lots of plants do not like it, but lavender, clematis and many fruit trees love it.
  • Peaty soil: dark, soft, waterlogged. Made mostly of partly rotted plant material. Very acidic and very high in organic matter. Found in cool wet places like Scottish moorlands.

How to tell what soil you have

There are some simple tests you can do at home.

  • Roll it: take a small lump of damp soil and try to roll it into a sausage. Sandy soil falls apart; clay soil rolls into a smooth shape that bends without breaking; loam rolls but cracks when you bend it.
  • Squeeze it: squeeze damp soil in your fist and open your hand. Sandy soil crumbles; clay soil keeps its shape; loam keeps its shape but breaks if you poke it.
  • Settle it: put a handful of soil in a jar of water, shake it well, then leave it for a day. The layers will separate: sand on the bottom, silt in the middle, clay on top, organic matter floating.
  • Look at the colour: chalky soil is pale and stony; peaty soil is dark and soggy.

What grows in each

  • Sandy: carrots, parsnips, potatoes, lavender, rosemary, herbs that like dry roots.
  • Silty: most vegetables, fruit trees, willows along rivers.
  • Clay: roses, hawthorns, asters, many fruit trees once established. Hard work to dig but very fertile.
  • Loamy: almost anything. The ideal all-purpose soil.
  • Chalky: lavender, lilac, clematis, cherries, apples, beech trees.
  • Peaty: rhododendrons, azaleas, blueberries, heathers, bog plants.
Fact Some of the most expensive wines in the world are made in vineyards growing on poor, stony, mineral-rich soils that would be useless for most other crops. Champagne grapes in France grow in chalky soil; Burgundy whites grow on limestone; many great red wines come from rocky clay-and-gravel mixes. Strong-flavoured wines often come from grape vines that have had to work hard to find water and nutrients in the soil.

Soil pH: acid or alkaline?

Soil also varies in pH (how acidic or alkaline it is) on a scale from about 4 (very acidic) to 9 (very alkaline). Most plants do best in slightly acidic to neutral soil (pH 6 to 7). Some plants strongly prefer one or the other:

  • Acidic lovers: blueberries, rhododendrons, azaleas, camellias, conifers.
  • Alkaline lovers: lavender, lilac, clematis, beetroot, cabbage.

You can buy a cheap soil pH test kit at a garden centre. Knowing your pH lets you choose plants that will actually thrive in your garden.

Did you know? One of the most surprising soil types is terra preta ("black earth"), a dark, fertile soil found in patches across the Amazon rainforest. It was made on purpose by indigenous Amazonian peoples between approx. 450 BC and 950 AD by mixing charcoal, broken pottery, bones and other organic waste into the natural soil. The result is unusually rich black soil that is still fertile thousands of years later, while the natural Amazon soil around it is poor and quickly worn out.
Deeper dive: why some farmland is much more valuable than others

Not all soil is created equal, and this has shaped human history in deep ways. Some of the most fertile soils on Earth lie in the chernozem belt across Ukraine and southern Russia, the volcanic soils of Indonesia and parts of Italy, the floodplain silts of the Nile in Egypt, the Mississippi in the US, the Indus and Ganges in India, and the Yangtze in China. Almost every major early civilisation grew up on one of these naturally rich soils.

Less obvious but just as important is what humans have done with these soils. Heavy ploughing, draining wetlands, planting the same crop year after year, and removing trees can all reduce the natural fertility of a soil over time. Some former breadbaskets (parts of North Africa, parts of the Middle East, parts of central Asia) became deserts partly because the soil was used up and washed away faster than nature could replace it.

This is one of the reasons people are now paying more attention to regenerative farming: ways of growing food that build soil rather than wear it out. Cover crops, no-till farming, crop rotation, planting trees alongside crops (agroforestry) and avoiding heavy chemical use can all keep soils healthy for the long term. A field that loses 1 cm of soil per year may seem productive now but is heading for trouble; a field that gains 1 mm of soil per year can keep feeding people forever.

For more, see layers of soil and soil erosion.