Horticulture Magazine

How To Break Up Clay Soil

compact clay soil that has been dug up

Heavy clay soil can be difficult to work with, but use the right strategies and techniques and you can still have a great garden.

One important thing to remember is that while heavy clay soils can bring some problems, they can also bring benefits too – each soil type has its pros and cons and clay soil is no different.

Some plants out there even love clay soil.

The good thing is that even when you have heavy clay soil, you don’t need to break your back digging and breaking it up to create a great garden.

Do You Really Need To Break Up Clay Soil?

no dig raised beds prepared for planting
Try No Dig Raised Beds Instead

If you are wondering about how to break up clay soil because you want to make a new garden bed then it is important to note that you might not need to at all.

Raised bed gardening means not having to worry about heavy clay soil at all.

And no dig gardening offers solutions that mean you won’t have to laboriously dig over a new patch.

raised beds with rhubarb plants and pumpkins in the background

Lasagna beds, hugelkultur mounds, and more traditional raised beds can all be excellent choices when creating new growing areas in your garden.

With existing clay beds, you often don’t need to break up the soil but can sheet mulch organic materials on top.

And with no dig gardening, the idea is not to break up the soil yourself, but to improve and maintain excellent soil health.

When there is a healthy soil, with a healthy soil web, the microorganisms and earthworms and other creatures living on and below the soil surface will do the work for you.

various vegetables growing in raised garden beds

They will make sure that the soil has a good structure, organic matter laid on the surface is incorporated, and air, water and nutrients are distributed effectively.

With a healthy soil web, and plenty of organic matter, clay soil can be great for growing a wide range of plants – with higher fertility than many other soil types.

In fact it has even been found that soils with very little clay can be “just as difficult to manage” as those with high amounts. [source]

Organic matter is food for micro-organisms, and micro-organisms are crucial for maintaining soil health and improving the soil.

Often, simply building up layers on top of the existing soil surface can be enough to overcome the limitations of clay soil, and can help you start a new garden without backbreaking work.

Natural Strategies To Break Up Clay Soil

1) Add Organic Matter

left to right - waste ready to be turned into compost

Compost is one of the most important sources of organic matter in a garden – adding plenty on the surface of the soil helps break up clay soil naturally.

On some occasions, however, a clay soil may be serious compacted.

The compaction may be severe enough that it cannot allow water egress and the materials piled on top may become waterlogged in wet conditions.

Where this is the case, it may be beneficial to ease that compaction somewhat before you create your new growing areas, or add sheet mulches of organic matter.

2) Fork The Ground

forking tough clay soil

Spiking the ground with a garden fork and gently easing the soil upwards a little can often be enough to open up water and air channels and begin the clay soil’s recovery.

This is far less invasive and so a better strategy than digging – it will leave space for a healthy soil web to develop once more as you build materials on top.

3) Use Plants

Using plants, however, might mean that you do not have to disturb the soil at all.

Certain plants – even commonly cultivated crops, are excellent for breaking up clay soil – potatoes, turnips, beetroot, and brassicas are all good options.

potatoes growing in a hard clay soil

Plant these in organic matter on top of the compacted soil and their roots can find their way down through into the compacted soil below.

Deep-rooted plants like comfrey, dandelion etc. are also excellent for opening channels down into clay soil to improve drainage and aeration.

4) Plough Furrows / Use Calcium

Traditionally, gardeners and farmers would often plough furrows to allow frost to break up clay soil over winter.

freshly ploughed clay soil

Sometimes, amendments like calcium are used, which can bind particles and reduce issues with some (but not all) clay soils. [source]

However, it is best to work with the soil you have and to use natural plant and soil-building strategies to improve your soil over time. [source]

Avoiding Soil Compaction On Clay Soils

young mustard plants sown as green manures
Mustard green manure

The main thing with managing clay soil is avoiding compaction issues in future.

The best way to do that is to take a no-dig approach and add plenty of organic matter.

Rather than tilling or digging over clay soil beds, keep soil as undisturbed as possible:

  1. Make sure you design so that you do not need to step on the beds.
  2. Keep soil covered as much as possible.
  3. Continue mulching between plants with organic matter.
  4. And use cover crops / green manures to protect the soil over winter and add organic matter in spring.

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