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Double dig or not?

 
Jen Shrock
pollinator
Posts: 363
Location: NW Pennsylvania Zone 5B bordering on Zone 6
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This spring I want to start to develop my site as a food forest Permaculture site. My yard is very flat with compacted soil. I have done a lot of reading and I am getting conflicting ideas. Would it be best to double dig to start and break up the compact soil? I have read that by just gradually building the soil, it might not allow the roots to penetrate and loosen the soil enough.

I do want to build the soil in lasagna garden style. If you double dug and then put a lasagna garden right on top, would it help protect the soil so that it doesn't break down in a damaging way?

Opinions and advise from experience would be appreciated.
 
Alice Kaspar
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Do not do all the extra work of double digging. That's why you do lasagna beds or hugul kultur. To AVOID double digging.
 
David Goodman
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Location: Zone 9a/8b
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I must respectfully disagree with Alice.

Double-digging allows your plants to get started and thriving right away. lasagna gardening is good long-term, but it's also limited by material availability. I would dig the areas you want to do right now, while mulching over the areas you don't have time for at this point. I've had instant results with double-digging that have me convinced of its efficacy. Do that, then mulch, and your plants will thank you.

 
David Goodman
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OH - and I agree with Alice. It IS tons of work. But that's also good exercise, so I don't mind too much.

 
R Scott
Posts: 3304
Location: Kansas Zone 6a
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If the soil is already dead, double digging can't kill any existing fungi or bacteria--all it can do is help.

 
Alice Kaspar
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Because we have heavy clay soil here on the Gulf coast, and rocky soil at our place in Missouri, double digging is just not in my plans. Ever. For me, there is no benefit.
 
Jen Shrock
pollinator
Posts: 363
Location: NW Pennsylvania Zone 5B bordering on Zone 6
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Part of my concern is more with planting fruit trees, shrubs and bushes that might get some significant size to them. My concern, if I don't double dig, is that they might end up just developing very shallow root systems and not have much strength to withstand wind and such. I think that I seen a picture on this site somewhere in which a very large tree was uprooted by wind and it's roots only penetrated down 15-18 inches or so because the soil was compact. I wouldn't be as concerned about general vegetables, but want to be sure that the larger plants are well grounded as they grow. I know that "opening up" the soil isn't optimal, but I thought that if you covered it back over right away with mulch and compost style systems, it would help to keep the elements from doing much damage until it developed it's new structure. I also was thinking that it might be a bit more inviting to earthworms and the like if it wasn't packed hard.

If I do end up double digging (which I probably will), would you put any compost/manure down in the soil before putting it back on top?
 
Morgan Morrigan
Posts: 1400
Location: Verde Valley, AZ.
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If soil is dead, double is good, otherwise you are killing off all beneficial bact/fungi.

If you want to dig, double down, and bury wood at the double depth. This will trap and save moisture and minerals.


dig, throw to side, cover.
double dig, throw in wheel barrow, move to raised bed somewhere.
fill bed with wood, and charcoal, preferebly activated. pour compost tea on wood and charcoal.
Lay in a loop or section of drip line, with tiny holes drilled in on opposite sides, every 8-10 inches, for deep watering in drought.
mix some compost and charcoal, and rock fertilizer in with rest of soil, and refill.

Lasagna top. cook for a year at 88 degrees.
 
alex Keenan
Posts: 485
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There is another aspect of double digging that I am not seeing anyone talking about.
Here is the issue based on research I did over a peroid of a decade.
Working in heavy clay there is a soil profile with high organic content in leaf litter and organic content decreasing as one goes down in depth to the subsoil.
Now if you make a bed for the long run the common practice is to add organic to the mix that you put back in the hole. So you dig the clay and abend it and put it back in the hole.
You then put in a plant that may be in the same spot for a decade or more.
Mulch or other organics are added to the leaf litter each year.
Now each year the organics in the amended soil will be consumed by microbes.
Over time the soil will revert back to something resembling the natural state of the surrounding area.
Now if your organics provided the soil structure you are likely to see the soil structure change.
In tests with hosta in heavy clay under trees with invasive root systems I saw the shrinking hosta.
Each year the roots got shallower and shallower.
Many hosta died.

At the same time I had double digs that I amended with, expanded shale, perlite, volcanic rock, biochar, and clean bottom ash.
In these beds the hosta did not change from year to year with the exception of getting root bound in some cases.

The pore space created by either inorganic or stable porous material was not subject to the rates of decay that the organic material was.
Just look at a good compost chart and it will give you the rate of decay for different organic material.

So when I double dig I do two twelve inch digs. The first I amend with porous and organic. The second dig I only use porous material that is slow decay or inorganic.
In areas with really poor drainage I just use inorganic porous material so I do not get the ponding effect. I then create a leaf litter area on the double bed.

 
leanna jones
Posts: 38
Location: Pennines, northern England, zone 7b, avg annual rainfall 50"
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i would dig a hole for each individual bush and tree, put in organic matter to the hole, then mulch around them. i would not do any other digging, i would just do the lasagne as you are planning.

i would sow some of whatever deep-rooted species are appropriate to your area (lucerne, chicory, lupin...?) in among whatever else you want to grow, this will break up the compaction and start moving nutrients between the layers. worms are strong and will sort it out for you in the medium term. the deep roots and the worms combined will allow your bush and tree roots to grow properly.

this is for veg gardens but some of it is relevant to all no-dig situations: http://www.charlesdowding.co.uk/
 
Pierre de Lacolline
Posts: 37
Location: New Hampshire; USDA Z5
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I don't have the heavy clay, but I do have rocky soil so digging is hard here too. One thing I have done is to use a heavy digging bar, punching it down into the soil and rocking back and forth to loosen up the top 8-12". (This is also helpful for finding rocks near the surface.) Add amendments on top of this. Last year I made a not-too-tall hugel bed (2' finished height) on top of ground that had been loosened in this way: loosen the soil, remove the big rocks, pile 1' of sticks on top, horse manure and leaves over the top of that, soil, and top dress with compost. The plum trees, comfrey, and various annuals from seed did really well even during a dry summer where I didn't water them much.

Less labor but more time would be to loosen the soil as mentioned above and then plant short-lived plants with deep taproots to break up the soil even more. For example, fodder radishes have very long taproots, grow quickly, and can help in this respect. Plant in fall, leave to rot over winter, and then use the holes that they leave behind as a way to get deeper with your bar (or do your double-digging at this time).
 
Tyler Ludens
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Morgan Morrigan wrote:
If you want to dig, double down, and bury wood at the double depth


I have had great success with this in heavy clay filled with rocks. A tremendous amount of work to excavate the rocks and replace with wood, but entirely worth it. Plants used to just die, now they grow well.

 
Roxanne Sterling-Falkenstein
Posts: 97
Location: Cave Junction, Oregon
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food preservation hugelkultur trees
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Start small, double dig only one area where you feel you need to work this year..perhaps carrot beds, beets, your spring stuff. Morgan is thinking when she suggests you add wood down deep while your at it, organic and in organic amendments..Like Davis says...mulch. I like composted mixed wood chips. Then I would begin to lasagna areas you plan to plant in later, they will begin to soften and develop for planting as you get to them. If you do have extra soil after a double dig, you could do a well covered small hugelkultur with a drip for this years squashes and start wild greens mixes on shadier side for summer salads. I would use this as an opportunity to compare what does best for you. I will use a digging fork sometimes just to lightly loosen but not turn to soil before mulching in really compacted never worked soil.
Never dig wet soil at all, always wait for soil to be in a crumbly state if you do decide to use the shovel or fork. When you plant trees, you want the hole to be the correct size and digging in with too much imported soil is not recommended. I am thinking to mimic an old tap root rotting away..an idea, a deep hole for a nurse-log or two ..deep down but vertically placed (post hole digger) under tree will act as a hugelkultur does holding water deep under tree longer and maybe helping create a spot for roots to go deeper, a lot of work tho. We have added drainage under trees in heavy clay in the form of oyster shell, volcanic rock powders and rocks from hole.
 
Jen Shrock
pollinator
Posts: 363
Location: NW Pennsylvania Zone 5B bordering on Zone 6
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All good ideas.

Roxanne - I have thought about loosening the soil with a digging fork as you mention. I am wondering if it would be enough. As you said, I could always experiment with a couple of different things to see what type of results I get with various methods. I found your post hole digging suggestion was a really interesting idea. You have made the wheels in my mind spin even more.
 
drew grim
Posts: 49
Location: pleasant garden, nc (zone 7A)
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all great ideas. if you have time, i have had great success planting diakons and letting them rot in the ground. it can smell pretty bad but it adds organic matter and does the digging for you. they break through our carolina clay like its nothing.
 
Jen Shrock
pollinator
Posts: 363
Location: NW Pennsylvania Zone 5B bordering on Zone 6
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I actually got a few daikon radish seeds specifically for the purpose of seeing how they can help to break up the soil. I am hoping to get a couple to go to seed so that I can increase the quantity I have available to use.
 
Neil Evansan
Posts: 69
Location: Valley of the Sun
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I agree with Pierre and Roxanne, dig DEEP below the trees you plant. If you can swing it, you might want to use a power auger and poke several post-holes in a 4' to 6' diameter. Trees like deeps roots for stability, but they also need wide roots to spread out past the canopy. For the other areas, I'd at least turn the soil before adding layers. For big-space areas, I've aerated hard-compacted soil with a 3/4"x24" woodworking auger bit (on a cordless drill) before putting down organic layers. and worms. (poking holes 8"-12" apart) In just a couple years, these yards were revived and healthy again. If you did this, I'd aerate before turning or double-digging.

We once tractor-tilled an old overgrown weeded backyard orchard (10 minutes south of Portland Oregon, 1/2 clay, 1/2 thick clumpy loam on a mild-sloping hillside) to turn & loosen the soil and allow it to breath. The first year was 'eh', but it allowed me to build planting mounds for Garden Food and Bonsai starters. The next year, 1/2 of the orchard trees revived (we thought several were absolutely dead). After that, the ground was awesome and the trees flourished (4 Apple, 2 Cherry, 1 Apricot, 2 Pear, 3 Holly) That was mid-80s. My former wife still lives there and grows about 1/2 of the food she eats, still all organic. The neighbors get boatloads of Fruit.

Good Luck with your land!

 
Jason Matthew
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I double dug three garden rows last year and added straw from the chicken coop and run. The results were nothing less than amazing. Having said that, I seeded cover crops from Grow Organic in the fall, using both the soil builder and sod buster seed mixes. Double digging heavy clay is slow exhausting work, and as someone already mentioned, you cannot create a permanent change in the soil profile. In order to maintain the organic matter, you are going to need to mulch and amend continuously. I believe that cover crops can do most of the work for us.
 
dj niels
Posts: 177
Location: CO; semi-arid: 10-12"; 6000 ft
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Every place is so different, and there are many approaches to try. My home garden is sticky clay, my market garden site 2 blocks away is pure sand. But under the top few inches of loose sand, is a layer of sand it is almost sandstone. The only way we've been able to get garden beds started is to use pick and shovel to break up the 1 to 2 foot layer of compaction. We just pull it all out, then fill up the bed with wood, hay, leaves, manure, and whatever else we can find.

The way to start might be to dig some test holes to see what your soil profile looks like. And just try a couple of small beds using different methods and see what works.
 
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