CARING FORYOUR SOIL

Good soil is essential if you want to produce healthy crops so this is the starting point for growing great fruit and veg. Here are some tips to keep your soil hale and hearty

Understanding Your Soil

It helps to know what type of soil you have. A basic gardening text will help you tell whether your soil is predominately sand, silt or clay (try searching www.rhs.org.uk for ‘soil types’), but also feel and listen to it when you are out on the plot. A sandy soil is gritty and falls through your fingers – you rarely hear it squelch. Clay is so sticky when wet that you can make models out of it. Silts are squeaky and slippery. You are stuck with your soil type – you can’t change it. However, you can change the soil structure.

In a well-structured soil, the basic particles of sand, silt and clay have formed larger fragments so it is crumbly – imagine breadcrumbs or making a topping to an apple crumble. The spaces between the crumbs allow air and moisture into the soil, and allow excess water to drain away, so plant roots and all the creatures that live there can breathe. When clods of a well-structured soil dry out on the surface, you can break them up easily with a fork.

ACID OR ALKALINE?

The acidity or alkalinity of a soil is basically the amount of chalk or lime it contains. This matters because it influences how easily plants can take up nutrients, and how comfortable it is for earthworms and other soil organisms to live there. The acidity or ‘pH’ depends on the soil type and area of country where you live but also on very local factors – your neighbour might be growing beautiful azaleas (a sign of an acid soil), but if your garden is on the site of an old building with lime mortar, yours could be very alkaline. A slightly acid soil (pH around 6.5) is best for veg growing.

If you are taking on a new plot, it is worth doing a pH test – use a DIY kit from a garden centre or, even better, send a soil sample away to a laboratory.

If a pH test shows that your soil is very acid, add ground limestone (garden lime) to the plot in winter as the results recommend. However, don’t automatically add lime every year. Although most soils will tend to turn more acidic over time, some materials which you already add have a liming affect – wood ash, municipal green waste compost, mushroom compost and comfrey liquid, for example.

Keeping the soil covered with growing plants is one of the best ways to build its structure. Pictured is grazing rye, an overwintering green manure crop

SOIL-DWELLING CREATURES

Turn over a clod of soil and you’ll probably spot several earthworms and perhaps a centipede scurrying away. If a robin comes to join you, his beady eyes will spot a few smaller creatures too. However, most life in the soil is microscopic, made up of bacteria, fungi, nematodes, mycorrhiza and other organisms with even stranger names. You can’t see them, but you can see the results of their work. They decompose organic matter, making nutrients available to plants. They help soil particles stick together, improving the soil structure. They form beneficial relationships with plant roots, effectively extending their reach so they have greater access to nutrients and water. Of course, there are also harmful soil microorganisms – some of them, such as white rot on onions, all too familiar – but in a healthy soil, the ‘goodies’ attack the ‘baddies’ or simply outcompete them for moisture and nutrients.

Earthworms have their own important roles. Those found near the surface (the smallest) help break down leaf debris. Those which live just below mix and aerate the soil and produce casts rich in nutrients. The largest deep-living earthworms make permanent vertical tunnels into which they pull debris, and these help to aerate and drain the soil. Regularly counting the number of earthworms in a spadeful of soil is a good way to monitor your soil’s health.

Howto Keepyour Soilhappy

Grow Plants In It

Living roots are best at building up the soil structure and feeding the community of soil creatures and keeping the soil full of plants at all times makes it feel wanted. Intercrop widely spaced plants with other quick-growing ones. Sow green manures in bare beds – annuals such as phacelia or mustard or overwintering grazing r ye can be sown in early autumn when summer crops are over. Think twice before clearing crops and annual weeds just for tidiness – if they are not harbouring pests or diseases or shedding seeds, let them grow until you need the space.

Wait until spring to add manure or compost to prevent nutrients leaching out

DON’T TREAD ON IT

Avoid compacting the soil, especially in wet conditions. Its light breadcrumb structure can instantly turn to heavy pancake, and you can almost feel it getting out of breathe. Even light pressure can cause a hard layer or ‘cap’ to form on the surface preventing seedlings emerging. Permanent beds which you can work just from the paths mean you never have to tread on the soil – they don’t necessarily have to be raised up or have posh edging.

Add Organic Matter

Compost and manure are food for the soil – for the soil-dwelling creatures and the plants – and they help improve the soil’s structure. However, don’t add them until spring otherwise the nutrients they contain will wash out over winter. A layer of leafmould, hay or straw is a better autumn cover for bare beds. You could use a mixture of fallen leaves and grass mowings. Woody plants such as fruit trees and bushes can be permanently mulched with coarser material – hay, bark, straw or shreddings made from small leafy branches.

DON’T DIG UNNECESSARILY

Digging turns the world of the soil dwelling creatures upside down. It severs all the drainage and aeration channels that the worms have made and the microscopic strands of fungi. Rotavating is worse, shattering the soil structure and creating a ‘pan’ (a compacted layer) at the depth of the blades. Dig new ground initially to break up hard layers and remove any woody roots, large stones and maybe even builders’ rubble! After that avoid cultivating wherever possible. Compost and manure can be spread on the soil surface, which will develop a crumbly ‘tilth’ making it easy to pull out weeds and sow seeds. Turn to page 10 for more information on the no digging approach.

Rotate Crops

The traditional reason for rotating crops on the veg plot is to avoid the build-up of pests and diseases, but it can also improve the general health of the soil.