Cultivating soil is not as straightforward as it may seem

Methods of cultivating soil and digging are used for different purposes. The more strenuous techniques should be avoided unless really needed. This is not just because they can be a strain on your back and heart, but also because they can be damaging to the soil.

Most often soil damage occurs due to cultivating at the wrong moisture level. Moisture 'lubricates' the soil particles and so high moisture levels when cultivating soil can lead to breakdown of soil structure and compaction of the soil.

The best way to avoid this problem is to wait until the soil is at what seems to be just the right moisture level for easy cultivation and then wait 3 or 4 days more! You are less likely to damage dry soil than moist soil, so always cultivate soil that is on the dry side of what you might otherwise think is right.

Simple Tilling of soil

The easiest and most common method to cultivating soil is to simply 'stir' it up a bit with a rake, tyned cultivator or hoe. This just moves things about a bit and is mainly used to help control weeds and incorporate fertilizer.

Avoid doing this simply for the sake of doing something. I knew one gardener once who spent all her time carefully turning and 'fluffing up' the soil. She asked me why her plants failed to grow and I had to point out that with every cultivation she was damaging their roots.

The first and most important rule for cultivating soil is: Do only what is Necessary - and no more.

Hoeing and Bed Forming

This involves moving and turning soil, but only the top 2 or 3 inches. The main use of this method is in preparing a bed for planting - especially when planting seeds. The objective for this method of cultivating soil is to break up any clods and even things up a bit. This should be all the preparation required throughout most of your crop rotation.

Deep Digging

This involves turning the soil over, breaking it up and mixing it thoroughly to the full depth of a shovel blade. It should only be done as part of the initial preparation prior to the first stage of your crop rotation. In fact, if you do things properly, it should only be necessary once every three or four complete rotations.

The most important thing is not to dig at all until you have soil tested and have applied the necessary treatments to improve soil structure and friability. This is not just to reduce the effort required, but also to prevent damaging the soil.

If you have not read our information on soil balance - do that now, before you get out your spade and start cultivating soil.

Trenching or Double Digging

This is the most strenuous and potentially damaging method of cultivating soil. It should never be done on shallow soils as it is always important to avoid bringing sub-soil to the surface. In fact, the only real use for this method is in raised vegetable gardens as part of the process of integrating (NB. I did not say mixing) bought-in topsoil with the existing soil beneath. It is something you should only ever need to do once.

You should also restrict your efforts to cultivating soil in a small area at a time - unless you are into body-building, then 'go-wild'.

Let's say you are working on development of a 12 inch raised bed, so that you can increase the depth of available soil. You are also wanting to use the "Bio-intensive" method to maximize both productivity and moisture retention.

If you followed the instructions on the page about raised vegetable gardens , then you will have:

1. Soil tested and treated the existing soil to improve structure and friability
2. Soil tested and treated the bought-in soil after you finished building the raised bed
3. Worked through at least one full crop rotation cycle

There will now have been plenty of time for the soil treatments to take full effect and for the biological community in the soil to recover from all the disturbance. The soil will also have had time to settle and you may well be thinking of topping-up with more soil.

If so - Don't! It is not soil you are lacking, its probably organic matter.

However, even the best soil test does not always get everything 100% right the first time. As soil changes, so do its requirements and so you may notice that you got an initially good result in terms of structure and friability, but now it has gone backwards a bit. If this is the case include a half-rate repeat of the treatments recommended on the soil test as part of the digging process.

Another thing to bear in mind is that, if your soil improvements included the use of Gypsum , the problems of the bought-in topsoil, may now well have moved down into the natural soil beneath. for this reason, the gypsum application used on the topsoil will now be applied to the deeper soil - once we get there.

So here is the double-digging process for cultivating soil in detail:

1. Spread a half-rate repeat of the soil improvement treatments for the top soil over the entire area to be dug (if necessary)
2. Dig a trench one spade deep (or down to the level of the pre-existing soil beneath the raised bed) along one side of the area to be dug over and put this soil on top at the far side of this area (to be used later)
3. Apply any Gypsum treatment recommended for the topsoil to the lower level soil, together with a generous topping of garden compost and manure (horse manure is best)
• Check the area of your trench and work out the right amount to apply - don't just guess. Remember, you do not ever want to do this here again.
4. Work these applications into the lower level soil to about one spade depth
5. Turn the adjacent topsoil into the trench (effectively moving the trench across by one spade width)
6. Repeat steps 3, 4 and 5 as you move across the area. When you get to the far side, turn the soil you first moved into the trench.
7. Now apply a generous topping of the compost and manure you used on the deep soil, to the surface of the topsoil and dig this in thoroughly.
8. Mulch with straw and leave this area alone for 4 to six weeks before planting

Check out this video of one of our recent double-digging projects:

One final note:

Minimizing the amount of time spent cultivating soil is a good thing, but even if you are wanting to have a 'no-dig' vegetable garden you should start by improving your soil first, digging if necessary to complete that process and then set up your no-dig bed.

For more information, there are some useful links below. However, you can also keep up with the latest information by subscribing to our email newsletter - The Food Gardener.

Further Reading:

Using materials like kelp and humic acid for soil improvement.
There are a lot of claims made about the use and effects of bio-active materials such as kelp, humic acid and fish emulsion. Here is what real research tells us.

The composting process explained
The production of good garden compost is not difficult, but requires more than just dumping a whole lot of stuff into a compost bin.

The use of green manure and cover crops.
Green manure is a valuable method for improving soil organic matter and biological activity.

Setting up effective crop rotations.
Crop rotation makes the best use of your soil with the least fertilizer input, while also controlling soil-borne disease.

Managing weeds without chemicals.
You now have optimally balanced and highly productive vegetable garden soil. Organic weed control is one of the techniques that will help you keep it that way.