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To dig or not to dig......

In the words of the world renowned gardener Mr William Shakespeare To dig or not to dig that is the question. Ok well that's not quite what he said and I know he might not have been a gardener but what we’re going to look at are two schools of thought when it comes to cultivating our soil.

Now for a long old time we’ve always been told all bare soil is suitable for cultivating (or digging). My grandfather used to do it every year and even today, up at our allotment, there will a plot holder or two who will be “putting their back into it” and will be carefully and religiously digging away.

But why do we do it?

Well soil cultivation - digging - is mainly carried out to bury or remove weeds. The surface is then usually surface prepared by being raked for sowing and planting. Cultivation also improves soil structure by alleviating compaction and it also offers the chance to apply fertiliser, manure and lime.

However only minimum cultivation is needed because over-cultivating can actually damage the soil structure and if we’re digging too close to roots of established plants then they might become damaged.

Digging is called 'primary cultivation' – using a spade or fork or even a rotovator. This is then followed by secondary cultivation to produce a fine seedbed, ready for sowing seed or planting. Here we use a rake and rake the surface back and forth until all the stones can be removed and the surface is nice and fine.

Another reason for digging is to try and improve the structure of our soil. That’s important so that our soil is not too compacted and that it’s reasonably free draining. If the soil is compacted and not particularly free draining – like a clay – then when it rains the water displaces air from the spaces between the soil particles and plant roots can drown.

When do we do it?

Clay soils are best dug in autumn, and it’s best to avoid doing this when the soil is wet. Autumn digging allows the frost to break up the soil over the winter and further improve it’s structure.

If you’ve got light, sandy soils then these are best dug in spring. However, digging can be carried out from autumn to spring, as long as the soil is not too wet or frozen.

How do we do it?

Well you could consider hiring a mechanical rotavator to do the cultivation for you if time runs short or if you have a larger area to cultivate. Light soils can be handled by a two to five horse power model, but hard or heavy soil needs a larger model. Rotavating wet soil does more harm than good and it’s best to wait for drier conditions.

Or you could use a good old spade and fork. And here we have two choices – single digging or double digging. Single digging is when you turn over the soil to a spade’s (or fork’s) depth and it’s easy to do. All we do is mark out a rectangular plot, mentally divide it into two strips, and lift a small trench, about a foot wide, and a spade’s depth, from the end of the first strip.

Place this soil to one side, leaving the trench empty. Then lift the same amount of soil from the area just behind, and drop it back, upside down and chopped up a bit, back into the original trench.

Work down the first strip, and then back up the second one, turning each trench into the space before it and then, at the end, the final trench is filled with the soil that was left to one side from the first trench.

That’s single digging. So what’s double digging? Well that’s similar but this time it involves inverting a second, deeper layer of soil. This is often hard work but its great for creating new borders and deepening shallow topsoil. It can also be helpful where drainage needs to be improved or where deep-rooted, long-term plants are to be grown, such as asparagus and rhubarb.

Digging your soil deeply also provides an ideal opportunity to incorporate some well-rotted manure or garden compost.

Is there an alternative? What’s this no dig method I’ve heard about?

Well let’s have a look at that – something that a now well regarded Somerset gardener has been an advocate of for ages. His name is Charles Dowding and he’s had a garden between Castle Cary and Bruton for quite some time.

So why does Charles advocate a no dig approach, and what is it?

Well he argues that every time the soil is dug then it recovers from the disruption by re-covering with weed growth – both from roots of perennial weeds and seeds of annuals. Those weed seeds that we’d hoped we’d buried deep beneath the surface have in fact been woken up from their slumber and are ready to germinate.

He also argues that the soil structure does need to feel firm or even hard, and that this is in fact fine for plants to grow in. He says that within the firmness will be a tight structure of fine air channels and root passageways and that plants root better in dense, firm soil than in one whose structure is loose and offers less support to the plants above.

How do you do it?

Firstly you might have to do some digging. If you've got deep rooted weeds like dock then it's best to dig them out.

Then you need to lay a nice thick layer of cardboard that will initially act as a weed barrier.

On top of that you add another nice thick layer – this time an organic compost or manure.

And then, and If you’re in no rush to get your beds into production, you can then add a temporary layer of black polythene. This will also act as a weed barrier as it will keep sunlight away from any weeds seeds that might want to try and germinate.

The temporary black polythene also encourages the worms to come to the surface and then start to drag that organic matter back into the actual soil.

What did I do?

When I first took on my plot at the allotment I sheeted off those areas where I wanted there to be beds. Before I did that I used a sharp spade to dig out the deeper rooted weeds – like dock – and then I covered the entire area with black polythene. And it worked a treat as in 6 months time most of the weeds and grass had been cleared.

Impatience though then got the better of me and rather than lay some cardboard down and add some organic matter on top I dug it all over and started planting…. A bit of no dig meets dig I guess.

What should I have done?

With hindsight – and even though I am partial to a bit of digging – what I should have been is more patient and tried that no-dig approach – cardboard, mulch and black polythene. I should have let all of that blend into one, and then taken the polythene off and then every year simply completed some very light weeding and added further layers of mulch.

What's my plan now?

I have three beds at my allotment. One already has some broad beans, onions and garlic growing away. The other bed has been largely cleared and is ready for planting up, and the third bed has become a wilderness of weeds. So I’m going to do this:

  1. The bed that’s planted up will stay as it is – for this year.

  2. The second bed that’s ready for a further light weed will have that – and then I’ll add some organic matter and then plant that up later in the spring.

  3. And the final bed will have any docks dug out. I’ll then carefully level it and then I’m going to sheet it over again to kill off whatever remains.

And then next year my plan will be this.

  1. The first and second beds will be my own experiment. One will be dug over and the other will follow that no-dig approach. It’ll have a sheet of cardboard and then a thick layer of compost. And both will have exactly the same crops and we’ll see what works best.

  2. And the third bed – the weed bed – will by then have had the black polythene removed and will have been levelled nicely. And I’ll do the same no dig approach there but this time I’ll simply grow cut flowers.

And we’ll see how that goes! I know I’ll need to add some borders to the beds as the surface layer starts to build up every year through the addition of the compost. And ideally I’ll need to be on top of my compost producing game as I’ll need more compost every year to add to the beds.

I’ll also need to produce different types of compost – some that’s finer in texture that I’ll need to add as my final layer and that will allow me to sow my seeds directly into it – seeds will germinate better in a finer compost than they will if the compost is thick and in clumps. But I’m hoping that after a few years I’ll have some highly productive no dig beds that will mean less time digging and weeding and more time just sitting and watching the world go by.

That's the plan at least..........

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