Who else would like to make their vegetable beds more productive?
And by productive, I mean not only will they produce a greater quantity of vegetables than they currently do – but those vegetables will have a wonderful flavour too.
If that sounds unrealistic – more vegetables, greater taste – then you’ve obviously never heard of a soil preparation technique called Double Digging.
So What Is Double Digging
Double digging is a soil preparation technique where you cultivate the soil to twice the depth of the average spade or fork. On a large scale, the benefits of a no-dig approach could be argued
But on a small scale where space is at a premium, we can achieve a much higher yield if we go to the effort of double digging.
Double Digging And Deep Beds
A deep bed is a normal bed – but one that is created using double digging. This creates a less compact, but deeper cultivated bed. This deeper cultivated bed is capable of growing vegetables much more closely spaced than a traditional bed.
This increased density of planting leads to an increased overall yield – and also you need to do less weeding, and the weeding that you do have to do is much easier and less time consuming.
The depth of a bed that is created by this double digging method is approximately twice the depth of a spade blade.
One thing to note – and this is vitally important – in a bed that is created using the double digging method the soil is not compacted.
So How Do We Double Dig?
The first step is to mark out your deep beds.
These should be a maximum of 4 feet wide. The length depends on the available space you have to work with in your garden. But an important point to note is to allow space to ‘cross’ at the end of the bed – or provide some other means of crossing the bed to get to the other side. Walking on the deep bed will compact the soil and defeat the object of double digging in the first place.
Next, push your spade into the soil to the full depth, lift out the soil and place to one side (either on the path or into a wheel barrow). This leaves a square hole the approximate depth of the spade, and with similar dimensions.
You may find in compact soil that its easier to push the spade into the soil on three sides, so completing a square before you actually turn the soil over.
Repeat the process across the width of the bed. You will now have a trench the width of the bed one spade deep.
Repeat with another trench directly behind the first placing this soil on a path or in the wheelbarrow. This leaves a trench as wide as the bed and about two feet (50cms) along the length of the bed. This first dig is the removal of the ‘topsoil’ and exposes the soil at the bottom of the trench
Now take your garden fork and push to the depth of the prongs. Turn over and break up this soil – but DO NOT mix it with soil from the first spade depth. This forked soil is sub-soil – and often contains far less active life and nutrients than the top soil.
In the majority of soils, the quality of the top soil can be improved and in some old kitchen gardens the ‘top soil’ can be three feet deep and teaming with life.
Next, place a layer of either animal manure,garden compost or green waste into the trench on top of the broken up subsoil. This creates a reservoir for water, along with nutrients and food for worms and soil organisms that will help make your deep bed productive.
Start another trench and turn over the soil on top of first trench. You will notice that the manure raises the soil level – and this leads to the name ‘deep’ beds.
Break up soil but don’t ever walk on the bed! This is why the deep beds are only four feet wide. All planting, weeding and harvesting is done from the sides. And there are instances where deep beds that are three feet wide would be preferable.
Continue with this process until you reach the end of the bed. You will notice that the last trench has no ‘top’ soil and this is where we use the first soil that is in wheelbarrow or on the path to finish the bed.
When you have finished the process then rake the surface of the deep bed roughly smooth.
The deep bed is now ready to plant up. Alternatively, in the autumn you could plant a green manure as bare ground loses nutrients.
How Often Do I Need To Double Dig
With deep beds you should only need to double dig approximately every three years.
In the intervening years all you need to do is single dig in the autumn, and add compost or manure.
You will that a deep bed prepared with the double digging method will not only be much more productive than a shallower bed prepared with just single digging, but the quality and taste of vegetables grown in these deep beds will be significantly improved.
If you have any questions, please don’t hesitate to shout up by using the Comment Form below this post.
At some stage soon I’ll create a video tutorial of the Double Digging technique and include it in an episode of The 10 Minute Gardener.
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