Wednesday, 8 August 2012

Why gardeners dig part 2: to expose soil to the action of weather


Winter Digging
This is carried out in Autumn to expose large clods to repeated freezing and thawing. This has a very real effect, it produces what old gardeners called a frost mould: beautiful crumbly soil. To benefit from this effect in Spring, it is important not to turn over the soil again. Get a seedbed by shallowly working through with a rake or fork.

What non-diggers say about this
1.) The effect is short term and anything that creates loose soil exposes crumbs to slaking down in heavy rain, exposing  the soil particles. It is important to understand that soil crumbs are just loose associations of particles and are notoriously unstable. Never produce excessively fine seedbeds, they tend to ‘cap’ after rain and bake hard in the sun. 
2.) After a year or two, although non-dug soil is firm and settled, accumulated worm casts make it easy to create a seedbed.
3.) Non-dug soil still gets some benefit from the cold.
4.) Non-diggers do not like leaving bare soil open to the leaching of nutrients. We would rather grow plants!

Important technical note: before we children throw our toys out of the cot arguing, let us be clear of one thing. Most soils are mixtures of sand, silt and clay particles. Nothing the gardener does changes the fundamental nature of these particles.

This gentleman strongly disapproves of non-diggers. 
He is chairmen of the diggers fan club!

26 comments:

  1. Love him! A garden full of blackbirds is always the sign of good soil.

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  2. Hi Poppy, I have been waiting (rather nervously) for your next post.
    We have just bought a small parrot-well a love bird actually. He is absolutely gorgeous, I can hear him singing now.He is going to love our conservatory when he builds up courage to leave his cage. We have called him Poppy. I hope you don't mind.

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    1. I'm flattered! But I'd never have known if you hadn't said anything! :-)
      Quite a name for a chap to live up to!

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    2. I like the irony in your reply. I did not like to describe our Poppy as 'it' but we do not actually know whether it is a boy or a girl!
      As I write Polly is flying over my head.

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    3. You'll have to post some pictures!

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    4. Yes I cannot wait to get a picture of him perched in our conservatory!

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  3. Re point 4 - I suspect that you negate the no-dig argument with this one. Surely one of the main ADVANTAGES of non-dug soil is that we CAN leave it bare without fear of the nutrients leaching, unlike turned soil?

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    1. Precisely Brett. I also follow the no-dig method and one of the things that I get smug about with other gardeners is the fact that I can leave soil bare without fear of damaging it. Not that I do leave it bare very often because I too, like to see a full plot of vegetables!

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    2. Thanks both of you.Good to know somebody is thinking out there. I can be persuaded a non-dug bare soil leaches less nutrients and certainly over long periods retain its structure. I was not really aware however, that winter leaching of nitrogen was prevented other than by growing plants. Perhaps you could enlighten me why none digging helps. I quite agree of course that nitrogen as a component of organic matter is not leached out and as organic matter decays with cultivation leaching increases.
      I particularly agree with Brett about a plot full of vegetables AYR.

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    3. Reckon you'll find more than a few thinkers out here!
      Whilst agreeing with the gist of your post, I agree with Brett that on point 4 you are trying compare the unplanted soil of a dig gardener (who then winter digs) with winter PLANTED soil of a no-dig gardener. It's apples and pears and cannot be done! Brett's point is that if BOTH gardens were bare, the undug one would leach LESS nutrients (he doesn't assert that it wouldn't leach at all) and I agree. I am assuming that all three of us are no-dig gardeners, but you seem to be arguing the dig gardener's point of view on this one - not that I'm unused to arguing no-dig with diggers!

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    4. Thanks for this Grant. I do not want to give diggers support, although I do want to be fair.(I love arguing with them too,especially when it's my brother-in -law, Dave.We both thump the table!) The point I would have liked to make was I hate to go round allotments in September and see all those dug over plots with no vegetable in sight. All that loss of nutrients and all those gorgeous winter vegetables not grown!We all seem to agree on this.
      I understand Brett's point and I would like to be persuaded he is correct that undug soil leaches less, (and I think he might be right). But what is the explanation? I think I am getting there, we non diggers have higher natural levels of organic matter and this will hang on to more nutrients. Or am I missing
      something else?

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    5. I meant to say' missing something else'!

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    6. I think Grant has articulated my thoughts better than I could myself! Obviously I would never assert that undug soil NEVER leaches nutrients, just less so than dug soils. I feel that this is because the organic mulch left on bare soil by no-dig gardeners not only replenishes more N-P-K than is lost through leaching, but increases microbial (and worm) activity and preserves soil moisture. This, in turn, allows undug soil to hold on to more of it's nutrients. However, I do admit that most no-dig gardeners prefer to use nitrogen or hold it on site as plant biomass in winter!

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    7. Thanks again, I am convinced. But then I want to be!

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    8. I think we're all of like mind. Brett just sounds as if he's done the math!

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  4. I only do winter digging to get out of having to help the wife prepare the Christmas dinner!

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    1. If my husband is anything to go by, you'll be far more use in the garden than the kitchen Simon!

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  5. Helen Borthwick9 August 2012 at 16:30

    I've been watching this debate progress with interest. I now have a question of my own. What benefit DOES non-dug soil get from frost?

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  6. The suggestion in the blog was that traditional winter digging by creating large clods (and thereby exposing a greater surface area to the elements) improves tilth formation in subsequent Spring seedbeds.An underlying assumption would be that the freezing and thawing breaks up the compacted clods. The argumentative point I made was undug soil is still to some extent affected by the same influences of freezing and thawing.
    In as much that we none diggers claim we already have good soil structure (and don't have any compaction), the answer to your question is probably 'not a great deal of benefit!'
    I guess that is what you already thought! Sorry.

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    1. I would thinks that non-dug soil, with it's rich surface layer of organic matter, would probably be less exposed to the freeze thaw cycle?

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    2. Yes you are right. On reflection I think my original point might be more relevant to someone in transition to no dig. Many of the advantages of not digging appear with time and in the first year a little help from freezing/thawing might help.

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    3. Possibly so. I suspect that the maintenance of surface residue also increases biological activity by protecting the soil from temperature extremes. The downside is that the soil appears to take just that little while longer to warm up in the Spring!

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    4. Have you noticed a corresponding retention of warmth in the autumn Helen?

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    5. Hello Grant. Yes, I have! It allows me to plant winter tares really late in the fall for overwintering.

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    6. Roy Sinclair, Snettisham14 August 2012 at 09:39

      Ah - green manures. I love them. Phacelia is my favourite, just for the smell. You couldn't ask more from a plant - smells beautiful, a magnet for insects and good for the soil!

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    7. I love it too Roy. It seems such a shame having to cut it all down before the flowers seed! I always leave a couple of plants just for the bees - that's my excuse!

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