To dig or not to dig

I frequently hear about the value of using a no-dig system when growing vegetables, but a recent post by Deano on his Sustainable Smallholding blog has made me think quite a bit about this issue and about the entrenched ideas that can permeate specific approaches to gardening (or any other aspect of our lives).

If you have read much of this blog, you will know that I am interested in permaculture and using this approach for designing systems in my gardening and elsewhere. Often, in the permaculture world, one finds reference to no-dig systems. The idea is that, in nature, productive systems are able to establish and thrive without any turning of the soil like we use in traditional gardening and agriculture. In order to emulate natural systems, the principle is that organic matter applied to the surface of the soil becomes incorporated into the soil structure by the action of worms and other soil fauna; just like it would in a woodland.

Woodlands produce organic matter that is incorporated into the soil by the fauna

The theory is sound, but in practice it may not be the best option. Natural systems have no ‘agenda’ – the vegetation that develops on a soil is the one that can thrive there. When we garden, however, we have specific aims and a specific time frame: it’s no good having to wait for 30 years for a deep fertile soil to develop when we need to feed ourselves now. Usually the reason for digging is to loosen the soil and to incorporate organic matter. It is true that, in some soils, worms and other soil animals can do this quite quickly, but it is not the case for all soils, as Deano has demonstrated with his heavy clay soil. Clay is a valuable component of soils as it is mineral-rich, but it is also sticky, impedes drainage and dries rock hard, and when it is abundant in soil, it creates a difficult environment for worms. Its presence is to be valued but, like most things, in moderation. Other components of soil – sand, silt, organic matter, water and air – are also important. The addition of organic matter to a heavy clay soil can help to improve aeration, fertility (including the release of chemical elements from the clay) and drainage. Given enough time, worms will do the mixing for you, but if you need it to happen this year, then some mechanical incorporation is the answer.

One of the arguments against digging (or ploughing) is that it damages the soil structure and adversely affects the habitat of the soil fauna. This is, indeed, true. For example repeated ploughing can lead to the creation of a hard, impermeable ‘plough pan‘ at the depth that the plough reaches because it smears the soil at this level. In addition, digging or ploughing causes physical damage to soil fauna and flora – potentially killing worms and chopping up fungal mycelium, mixing up soil micro-organisms, exposing buried organisms to the surface and burying those from the top layers.

So, there are pros and cons… the essential issue is that you must know and understand your soil in order to select the right way to manage it. You must also understand what you need from your soil. It’s about making informed decisions. And this is, perhaps, the real issue: we should not allow sensible ideas to become dogma. There can never be a single solution that fits all situations, and by making rules and being prescriptive will inevitably lead to disillusionment when that answer doesn’t  work.

It’s not just humans who dig!

In fact, I don’t dig my vegetable beds much because, as I have mentioned before, there was very little soil in my garden when we moved in so we build raised beds. The imported soil was light and friable and supports large numbers of worms, which do mix organic matter in quite quickly. Having said that, however, I do dig. I particularly like in situ composting involving digging a hole and burying fresh organic matter – a mix of material high in nitrogen plus something like wood chip or shredded paper to provide carbon and improve structure – especially when I’m planting runner beans or members of the squash family. And sometimes I dig in compost for a quick addition and to stop the chickens chucking it around all over the place. Talking of which, the chickens do quite a lot of digging too!

But, perhaps I need to get to know my soil better in order to make more informed choices about how I manage it and, with this in mind, I’m going to be testing the pH of my beds soon and I will be thinking a bit more about the structure and texture of the soil.

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