Beginner gardeners could be forgiven for thinking that soil is just, well soil. That’s fair enough I suppose, as most soil does look similar at a glance. But dig beneath the surface and you’ll discover that soil can vary enormously in its structure, consistency, fertility and ability to hold onto moisture.
You might wonder why the make up of your soil is important. Well, it has a huge impact on the kind of plants that you can raise, and it determines how well they grow. For example, plants usually romp away in fertile soil that’s in good shape, while those set in infertile soil tend to limp along before giving up the ghost.
What kind of soil
The three most common types of soil are clay, sandy and silty. You can find out what kind of soil you have by digging up a little and rolling it into a ball. If it’s sticky and easy to mould, then it’s clay, while soil that feels gritty and doesn’t hold together well tends to be sandy. Balls of silty soil hold together and have a distinctive silky texture.
Clay soils are fairly fertile, but heavy clay can become waterlogged in winter and dry rock solid in summer. It can be improved by digging in plenty of well-rotted manure and a few handfuls of grit, which will improve its drainage and enable it to hold onto moisture more effectively in summer, prevent it from turning to concrete.
Sandy soils benefit from having well-rotted manure or garden compost dug in. This bulks up the soil and enables it to hold onto nutrients and water more effectively, allowing it to reach the roots of plants. Digging the same materials into silty soil will help improve its structure and prevent it from compacting too easily.
Acidic or alkaline?
Gardeners often talk about soil acidity or pH. Very simply, soil acidity is recorded on a pH scale of 1 to 14. A pH of 7 indicates that the soil is neutral with scale points above this being alkaline and anything beneath it signalling that soil is acidic. Most plants prefer a pH of between 6.5 and 7. You can discover the pH of your soil with a testing kit.
How to keep your soil healthy
Soil requires a little bit of attention to keep it in good shape. If it’s regularly cultivated mulch it annually in autumn or spring with a 7.5cm (3in) layer of garden compost or well-rotted manure. As it breaks down, it will improve the fertility of the soil and encourage worms and microorganisms. Rain can literally ‘flush’ nutrients out of the ground, so after a wet winter work organic matter into the ground with a fork.
Choosing top soil
High in nutrients and organic matter, top soil is the uppermost layer of soil. It’s available to buy in bags or in bulk, and is useful if your soil is poor, exhausted or you have a space without any natural soil, such as a courtyard. There are three different grades – premium, general purpose and economy. The first is most expensive but best for new beds as it has been screened to remove weeds and stones.
Dealing with builders rubble
A problem faced by many owners of new homes is that they inherit beds and borders where a layer of thin soil has been laid over builders’ rubble. Aim to boost its fertility by adding garden compost or well-rotted manure, and choosing plants that don’t need rich soil and that like free-draining ground. Lavender, rosemary and other Mediterranean species are perfect.