Ditch the Double Digging?

raymondo17(z9 Sacramento)August 26, 2014

Every spring, and then again every fall when the season's harvest is over, I double-dig my raised beds: I clear the beds of all remaining plant material, then plunge a shovel into the soil and dump it to the side of the hole. I continue this until all the soil in my 4' x 8' bed has been turned. Then I sprinkle a bag of composted cow manure, peat moss, compost, bone meal and blood meal on the soil and repeat the process to mix the amendments in. I thought this was a means of replenishing the nutrients and improving the soil. But I just came across a video from my revered gardening guru, Paul James, that suggests that I may be actually harming the microorganisms in my soil. He suggests to instead use a pitch fork or broad fork to "stab and rock" the soil, basically aerate it. It certainly would be a less labor-intensive approach than my double-digging, but I'd like to hear from others who take this approach.

Here is a link that might be useful: Gardener Guy Video

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jean001a(Portland OR 7b)

You only need to double-dig once.

    Bookmark   August 26, 2014 at 11:05PM
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grubby_AZ

If that.

    Bookmark   August 27, 2014 at 12:07AM
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raymondo17(z9 Sacramento)

So if double-digging is detrimental to the soil, how would one add amendments? Just pour them on top, maybe scratch them into the surface?

    Bookmark   August 27, 2014 at 2:43AM
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renais1

I ditched the huge work of double digging, and found that the garden did much better than when I was doing all that work. I found that the garden did not even need an initial double dig in areas that previously had been untouched. What I did was to till the old growth under, and then cover the area with a thick layer of organics, mostly manure, but other materials as needed for the soil. I would then till the mixture once more, cover again with organics as a mulch, and plant. The soil critters did the work for me. I was always amazed that I could put my hand down into what was formerly a pretty solid clay soil so easily. Water was absorbed quite well, and plants grew beautifully. I actually found that the double digging seemed to reduce the organics in my soil too quickly (an observation made by others who use the technique as well). In addition, I would find that the beds sunk a good bit over the course of the season. I will probably never double dig again. By the way, I started this practice after reading the Jeavons book on growing food; there were some good ideas in the book, but I think double digging was too much work, and did not provide the results I wanted.
Renais

    Bookmark   August 27, 2014 at 8:41AM
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dbarron(z7_Arkansas)

Strangely, for millions of years there were no gardeners to double-dig, and plants managed to thrive and evolve. Man can never do as good as job as Nature does in opening and aerating the soil with her microbes, worms, beetles, and myriad other creatures.

Turning the soil exposes new weed seeds, exposes subterranean organic matter (where it then starts decomposing and is lost), promotes soil erosion, and simply is an exercise for the impatient who require something to do all the time.

Now given that...it could be very useful to expose bermuda roots to winter temperatures if done during the hardest parts of winter.

    Bookmark   August 27, 2014 at 8:45AM
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Kimmsr(4a/5b-MI)

Once the soil is built up into a good healthy soil and has an active Soil Food Web they will move any nutrients you put on the soil into the soil. Double digging is a lot of work, often unnecessary, and can move the aerobic Soil Food Web down below where they can survive.
Where soils are walked and driven on and get packed down tilling might be necessary, but if the planting beds are constructed in a way that no walking or driving on is done tilling is not necessary, providing adequate amounts of organic matter are in the soil.

This post was edited by kimmsr on Wed, Aug 27, 14 at 11:32

    Bookmark   August 27, 2014 at 11:30AM
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toxcrusadr

I read something about that rocking fork method in Mother Earth news a million years ago. In fact I think Jevons had a regular column in that mag, or else they did a big story on his methods.

Yep, the microherd will do the tilling for you, once you get some amendments down there initially. If you have heavy soil (clay), which I do, it's best to leave the porosity in place that is created by worms and insects boring through - 'secondary porosity'. When you dig this is all destroyed. I've got my beds raised up about 4-6" after 20 yrs of amendments, and I don't dig much except for tree roots. When planting individual plants like tomatoes, I just dig a hole and amend that, and mulch with compost and organic matter. The micro herd then incorporates that into the soil. When planting seeds by the square foot (or sq yard) I'll dig in compost very shallow, rake and smooth the bed and plant.

    Bookmark   August 27, 2014 at 12:32PM
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raymondo17(z9 Sacramento)

Thanks for the great responses here.

>I would then till the mixture once more,Renais1, what's the difference between the tilling you do and double digging?

So the recommended course of action would be to spread amendments over the top of the soil and let it be? And the microorganisms will do the work, even the heavy lifting like breaking up the large clumps of tomato roots in the soil? This sounds too easy. :)

    Bookmark   August 27, 2014 at 1:54PM
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dbarron(z7_Arkansas)

By next spring, you won't be able to find those tomato roots (at least if they're under the soil).

The process is like a chicken laying an egg, looking under the chicken every five minutes, will not hasten the process and in fact may result in a broken or bloody egg.

    Bookmark   August 27, 2014 at 2:04PM
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renais1

I tilled the soil when I first prepared it so that I could kill the existing cover plants, and to begin to incorporate some of the organics into the soil so that soil critters would have an easier time getting to them. I used an 8 hp tiller so the tilling took very little time or effort compared to double digging. By tilling twice, separated by some time, I helped to insure that the old growth had been mostly killed.
Renais

    Bookmark   August 27, 2014 at 4:59PM
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toxcrusadr

Dead plant roots will decompose in place, leaving a network of tiny pipelines in the soil.

I don't mean to suggest you have to be a stickler about NEVER digging. Actually my experience was a gradual reduction in digging over time as the soil improved. And possibly as I learned about the importance of secondary porosity in clay soil. I have double dug my beds several times since I started 20 years ago, but won't do it anymore, except to get big tree roots out.

    Bookmark   August 27, 2014 at 5:33PM
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Kimmsr(4a/5b-MI)

Double digging is tilling. Not all tilling involves double digging, though.

    Bookmark   August 28, 2014 at 6:22AM
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ernie85017

Read One Straw Revolution.
He calls it lazy man's gardening.

    Bookmark   September 5, 2014 at 7:10PM
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wayne_5 zone 6a Central Indiana

I do utilize using a potato fork some to hasten drying in the spring to less amended areas. Yes, you dig in 7 inches and rock or lift a bit. This can be VERY helpful when adding amendments or even rotted manure. It lets some of the added things trickle down lower.

Just today I used a tiller to better prepare a plot for seeding tillage radishes.

    Bookmark   September 8, 2014 at 2:02PM
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Meuhey(zone 4a)

from this

    Bookmark   September 11, 2014 at 11:38AM
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Meuhey(zone 4a)

to this, if you have easy access to organic matter, no till is the best, garden was watered once at planting.

    Bookmark   September 11, 2014 at 11:39AM
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Embothrium(USDA 8 Sunset 5 WA)

Double digging involves bringing the subsoil up and mixing it with the topsoil, which is undesirable. You want all the fine particles that washed down into the subsoil to stay there, and to not be bringing them back up to the upper level where they then make it less aerated.

    Bookmark   September 11, 2014 at 11:45AM
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wayne_5 zone 6a Central Indiana

I thought that double digging does not mix the two.

I have seen some really lush weeds where there was some mixing by tiling.

    Bookmark   September 11, 2014 at 10:07PM
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