It’s not the most glamorous substance out there but soil, a mixture of organic matter, minerals, gases, liquids, and organisms, is a unique, life-supporting environment. A layer of soil covers the earth’s crust like protective skin. Soil coverage can range from a sprinkling of a few millimetres to several feet deep.
There are myriad soil types that have wide-ranging properties depending on their composition. We often talk about soils as being chalky, sandy, clay-like, peaty, silty or loamy. The 6 different soil types, and our interactions with them, have a huge impact on what can and can’t be grown successfully in your garden or plot.
Let’s take a closer look at each soil type and what it means for your growing patch:
Chalky soils are very alkaline and mainly consist of calcium carbonate. This soil type can be light or heavy and has a pH (the measure of acidity or alkalinity of the soil) of 7.1-8.0.
You might be able to see chalky deposits on the top of your soil but if you’re unsure, add a teaspoon of soil to a jar of vinegar and see if it bubbles, if it does, it contains chalk or lime.
Chalky soil is good for plants that like good drainage and aren’t particularly reliant on nutrients. When planting, add plenty of mulch and fertilise plants regularly.
Sandy soils are usually light as they contain plenty of sand and very little clay. This soil type drains easily and feels gritty to the touch. Sandy soil will have a pH of 4-6.
Because sandy soil drains freely, it doesn’t retain many nutrients. You’ll need to add organic amendments for the best growing results.
Sandy soil loving plants include tulips and hibiscus, and vegetables like carrots, squash and collard greens.
One of the tricker soil types, clay soil is thick, heavy and stays wet and boggy in winter while cracking dry in hot summers. This soil type drains extremely slowly but it does retain nutrients well. Clay soils are alkaline with a pH between 8-10.
I have this soil type in my garden and, although the grass is a no-go zone over winter (read bog garden); wisteria, jasmine, honeysuckle, climbing hydrangea, photinia, box, a grapevine, grasses and palms, ferns, lavender and a beautiful magnolia are all thriving in it.
Peaty soil is quite dark in colour and feels spongy to touch. It heats up quickly and retains water well. Peaty soil has a pH of 3.7-5.2.
Light, less acidic peat soils are among the most fertile and celery, carrots, onions and lettuce will grow happily in it.
Peaty soil can be found throughout the country from the highlands of Scotland to the Somerset levels but the demand for compost has made peatlands one of the most endangered natural habitats in the UK.
Silty soil is rich in nutrients and holds moisture well. Its fine particles make it soft to touch and it’s easy to work, making it perfect for planting. Silty soil can range from slightly acidic to slightly alkaline.
Most vegetables will grow happily in this soil type along with moisture-loving trees, shrubs, climbers and perennials.
The creme de la creme of the soil world, loamy soil benefits from a mix of sand, silt and clay in similar amounts. This soil is fine-textured and might feel a bit damp. Loamy soil has a pH of 5.5-6.5 making it slightly acidic.
Loamy soil has the right balance of nutrients, water retention, structure and drainage and is perfect for lawns and plants of all kinds.
How can I find out which soil type my garden has?
There are a few simple ways to determine your soil type:
Pour water over a patch of soil and see how long it takes to drain. Fast draining soils are sandy or loamy whereas clay soils will drain slowly.
Grab a handful of soil and see how it feels, clay soil will stick together, sandy soil will be gritty and crumbly, peat is spongy and loam or silty soil will feel smooth.
You’ll need a transparent, lidded container like a jam jar or large test tube for this test. Add a good handful of soil, top with water, shake and let rest for 12-24 hours.
- Chalky soil will turn the water grey and leave a deposit of white at the bottom of the container.
- Sandy soil will leave sediment at the bottom of the container and the water will be quite clear.
- Clay and silty soils will make the water cloudy and leave a layer of grit at the bottom.
- Peaty soil will leave floating particles in the water which will remain cloudy.
- Loamy soil will leave layers of different sediment and clear water.
You can also perform a pH test and kits are readily available from garden centres or online.
How do I know if my soil is healthy?
It’s difficult to grow healthy plants and bumper crops without healthy soil. Soil health is the ability for soil to function effectively as a living ecosystem that can sustain plants, livestock and humans. Soil rich in nutrients is usually dark brown to black in colour but you can dig a little deeper to discover more…
There will be plenty of worms
These wriggly wonders may make you squirm, but the presence of worms in your soil is essential for good soil health. Worms improve soil structure, water movement, nutrient cycling and plant growth. Dig up a few inches of soil, if you see more than 3 or more worms, it’s a strong indicator that the soil is healthy, no worms means there’s not enough organic matter for them to feed on.
Well covered roots
As roots are completely reliant on soil, their appearance is an excellent indicator of soil health. Pull up a weed from your garden or plot and look closely at the roots, are they covered with soil and well spread? You might notice crumbly soil is covering the roots, known as a ‘rhizosheath’.
It’s easy to work
If your soil is compacted and hard to dig, workability is low and chances are that plants and organisms such as worms will struggle to thrive there. Workable soil allows water to penetrate easily and reach the roots and it’s much less prone to compaction.
How can I improve the health of my soil?
There are several ways to improve the health of your soil, creating better conditions for your plants and the environment:
Tillage is a mechanical method of loosening and aerating soil before planting, think of rotavating before a new lawn is laid. Excessive soil turnover can be detrimental to soil health in the long term and is best avoided if you can manage your garden or allotment soil by hand. Avoiding tilling keeps biodegraded organic matter on the surface of the soil, helping the soil to maintain a structure where rain can easily penetrate. You can easily use a fork to loosen the top layers of soil without destroying the essential microorganisms before sowing or planting.
Grow cover crops
Bare soil is unhappy soil, try to keep the soil covered, even if you aren’t growing crops. The cover crop will help to prevent erosion and produce nutrients to enrich the soil.
Amend your soil
Most soil types will benefit from a regular addition of well-rotted manure or compost. Add a layer of at least 5cm and fork in well. You can also amend the pH of the soil and add sand to improve drainage.
Read more: What’s the best soil for a planter box?