Fixing your soil

Once you’ve assessed your soil and worked out what, if anything, you want to change, here are some tips on how to do it.

Problem: Poor drainage

Putting drains under your garden can be expensive, but if you have a high water table and/or very heavy soil, it may be the only way to effectively improve conditions. Drains take different forms, but the most common in gardens are French drains (drainage ditches with a permeable pipe at the bottom filled with gravel and topped with topsoil) and soakaways (gravel filled pits which drain excess water away into underground drains or ditches).

If the poor drainage is due to structure issues such as compaction or a pan underneath the soil then cultivating (digging) the soil as deep as possible (certainly below the depth of the problem) will ease it. Organic matter should be added at the same time.

Improving the soil structure by the addition of bulky organic matter (such as farmyard manure) can also aid drainage. Heavy clay soil can be ‘floculated’ to break the aggregates down into smaller sizes (thereby aiding drainage), which is done by adding lime to the soil (although this shouldn’t be done where acid-loving plants are growing).

Problem: Soil is too acidic

Acidic soil is generally dealt with by the addition of lime, usually in the form of calcium carbonate, calcium oxide or calcium hydroxide. The use of mushroom compost can also add lime to the soil.

Problem: Soil is too alkaline

This is a less likely problem, although it does occur. The addition of organic matter such as some peats or composted conifer bark will help to lower the pH of the soil. Alternatively a more instant effect can be achieved by using products containing ferrous sulphate or sulphur.

Problem: Soil is too sandy/silty

Clay can be added to sandy or silty soil to improve the structure (a process known as marling) and bulky organic matter (such as farmyard manure or garden compost) will also help to form aggregates.

Problem: Soil is too clay

The structure of clay soil can be improved by the addition of bulky organic matter (such as farmyard manure) which will help create spaces, breaking down the large clay aggregates, and allowing water and air to move through the soil more freely. Heavy clay soil can also be ‘floculated’ to break the aggregates down into smaller sizes, which is done by adding lime to the soil (although this shouldn’t be done where acid-loving plants are growing).

Problem: Soil lacks organic matter

You can add organic matter to your soil in many forms, the most popular being garden compost and farmyard manure. This can be dug into the soil or used as a mulch which will be gradually drawn underground by soil organisms (or a combination of the two). In a ‘no dig’ system, mulching is key and is often done in both the autumn and spring with around 10cm of mulch being spread over bare earth.

Green manure can also be used to add organic matter and is particularly useful for vegetable patches or allotments. Sow it when the ground is not being used for a while then dig it in when you’re ready to use the patch. Digging it in isn’t an easy job, but at least you won’t have to do any weeding while the green manure is covering the ground!

Problem: Soil is nutrient deficient

If you can identify what nutrient is deficient (eg due to plant symptoms) then you can use a fertiliser specifically aimed at providing that nutrient. If the plant is in a bad way then a foliar feed will give it an instant boost, otherwise a slow release fertiliser is best. These come in organic forms (eg fish blood and bone) which shouldn’t be used in containers, or inorganic ones (eg Growmore).

For general nutrient improvement, bulky organic matter (eg garden compost) should be added to the soil. The nutrient content will vary depending on what is used but the additional organic matter in the soil will also help to retain other nutrients, so you get a double benefit. Green manures can be used, in the same way as bulky organic matter, to add nutrients and nutrient retentive capabilities.

Problem: Soil is compacted

See poor drainage.

Problem: Soil has a cap on the top

If you have sandy or silty soil there are a few things you can do to avoid this problem:

Avoid walking or using machinery on it in wet conditions, which can break down the surface structure.
Don’t leave the soil bare; if you don’t have plants growing on it then mulch the surface or grow green manure.
When watering the soil do so using seep hoses or drippers stuck into the ground, rather than watering overhead with a hose or watering can, which can cause the same damage as hard rainfall.

Problem: Soil has a pan (underground)