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hard clay needs rehab to make garden

Jo Hager

Joined: Mar 15, 2014
Posts: 2
The ground here is hard-as-rock clay. I got a free dump truck sized load of pine and other tree chips, and spread that over where I want a veggie garden, and also spread compost there. My plan is to till that all in to break up the clay. Hopefull that'll loosen up the ground enough to grow something. Any other suggestions to amend the area? Tnx in advance!
Michael Cox

Joined: Jun 09, 2013
Posts: 1510
Location: Kent, UK - Zone 8
Jo, my experience of spreading woodchips was that the increased moisture and the increased wood habitat cured a lot of soil problems without any tilling in. Tilling will bury those chips in which can lead to the carbon locking up all available nitrogen making growing anything for the next couple of year hard. Chips on the surface don't tend to do that, and the worms will eventually work all that goodness in for you anyway.

If it was my land I'd:

Dig a deep test hole to see what the subsoil is like - are you dealing with a 6 inches of hard clay or is there a deeper hardpan that may need attending to as well?

If you are determined that tilling is necessary to break up damaged/poor clay soil I'd do that first then spread the chips on top, rather than spread the chips in.

Then consider planting soil improving crops for your first year - daikon radishes in particular have a reputation for sending deep strong roots that can bust apart compacted soils to quite a deep level.
John Elliott

Joined: May 08, 2013
Posts: 2170
It also depends on where "here" is. If you are in a warm climate where the ground never freezes, then it's not going to lock up available nitrogen for a couple of years, it will be mostly decomposed in a few months.

Other amendments you may want to try are:
-- Drywall. New home builders discard a large amount of drywall. Collect it and leave it out in the weather on top of your clay. In a few months, it will be crumbly and you can till that in as well, the calcium helps to break up the clay.

--Sand. Nice soils have a balance of sand, slit, and clay. Unfortunately, nature lets things get out of balance, so we end up toting what is missing in and incorporating it. It has to be done right though, if you add sand to clay in the wrong manner, it is possible to turn clay into concrete. If you do have some sand to till in, make sure you till organic matter in with it. With enough organic matter, you will not get sand particles cemented together with clay.

--Biochar. The terra preta soils of the Amazon would be clay, were it not for the large amounts of charcoal added by human activities. This charcoal also acts up break up the clay particles and increase soil fertility.
Renate Howard

Joined: Jan 10, 2013
Posts: 755
Location: zone 6b
My property has areas of terrible clay and areas of rich black deep loam. It appears it reverts quickly back to clay when left exposed. Find things that can grow in your clay and mulch them well and in a few years IMHO you'll have nice loam.
Jennifer Wadsworth

Joined: Sep 24, 2013
Posts: 2679
Location: Phoenix, AZ (9b)
Knowing your location would help a lot.

Here in the hot desert I have very heavy clay soils with a lot of salts and calcium in it.

I made the mistake of double-digging in some woody-ish compost. Although the woody compost did loosen help keep the soil looser, it also leached nitrogen (badly) from anything I planted in those beds for a full year (we grow year round in Phoenix).

Drywall works to help decompact soil in some areas (gypsum). It is not recommended for soils that already have high calcium (and yes - there is ongoing debate over this - my best advice on this came from a soil scientist for the NRCS in Tucson).

Planting a deep rooted covercrop suited to your climate will help break up your soil, add nitrogen, provide the soil with shade/cover. When you decide to remove the cover crop, leave the roots to rot in the soil as much as you can and mulch with the cut tops of the crop.

I have had really good luck with compost teas helping to make my soil texture better. I make big vats of it and use it liberally after watering an area.

Keep going on your mulch - microbes are interacting with it and will help build soil beneath it.

Subtropical desert (Köppen: BWh)
Elevation: 1090 ft Annual rainfall: 7"
R Scott

Joined: Apr 13, 2012
Posts: 3048
Location: Kansas Zone 6a
How big of a garden are we talking, in square feet? To know the size of the problem. What is affordable to you?

Do you have sand in the soil? Adding sharp sand can help open up the soil to let the organic matter work its way in.
"You must be the change you want to see in the world." "First they ignore you, then they laugh at you, then they fight you, then you win." --Mahatma Gandhi
"Preach the Gospel always, and if necessary, use words." --Francis of Assisi. "Family farms work when the whole family works the farm." -- Adam Klaus
Jo Hager

Joined: Mar 15, 2014
Posts: 2
Thanks so much for the tips The garden is about 20' x 30', and we're in SW Virginia, about 45 min. south of Roanoke. This past winter has been the worst/coldest in about 20 years. The amount of snow and negative digit temps we've had are very unusual. Usually it's fairly mild here, with temps rarely dropping below freezing. The area ranges from full sun to partly shaded. This is my first year here- I came from Sioux Falls, SD where I had lovely soil.

I wanted to buy topsoil, but when I got the estimate I realized I needed to find another way. That's why I chose the free load of shavings and adding my compost pile. I'd also have to cut down more trees to get a big truck back there, which was another issue. I moved that shavings pile, two 5 gal. buckets at a time, through the woods to the garden. I already cleared an area about 75' x 75' so I could have a garden, and I'd rather not lose any more healthy trees. The garden is built around remaining tree stumps that I'll work on decomposing/removing after this summer. We've got a total of 5 mostly heavily wooded acres. If I don't have to till it now, that'd be beyond wonderful. I'll also have free-range ducks to help fertilize the soil and eat bugs.

When I dug out the duck pond, I made it 18" deep. There was clay all the way down until 18" where I reached tree roots and some gravel/large rocks (look almost like granite) mixed in with the clay. At that point my back decided it was deep enough LOL. I haven't tested the ground for nutrient/chemical composition, but what currently grows well here are pine, oak, and I think some possible juniper trees. Also, some weedy bushes with long thin branches and thorns, which have small flowers like roses but are double petaled, will grow. You can cut them to the ground at any time of year and they'll immediately grow back twice as fast and spread like wildfire. There also are wild blackberries that also spread like crazy. Low evergreen bushes (might be spruce?) and azaleas grow here. I got some lilies to grow last year by digging out a trench and filling with potting soil. The ones I planted in the original clay ground didn't grow.

I'm not sure who does soil testing here, but I'll call around this week. I know where there are 2 large construction jobs going on locally, so I'll ask the guys this week about scrap drywall. Great idea about the daikon radishes. I found a place online with organic seeds so I'll also call them this week to see how much I'd need for an area that size. A load of sand probably isn't possible due to cost and the challenge of moving it to the garden by buckets. I'd like to pretend I'm Superwoman, but I'm not.

Hope that answers all the questions, and thank you so much for your tips!

-- Jo
John Elliott

Joined: May 08, 2013
Posts: 2170
Jo, your soil sounds a lot like mine, except I have only a little gravel and no large rocks. What really helps this soil is biochar. Since you have a lot of wood, you should think about turning some of it into charcoal and then turning that under. The most productive part of my garden is where the previous owners kept their burn barrel and dumped their charcoal. If I were to edit my previous post with this new information you give, I would put biochar in bold and underline it.
Andrew Schreiber

Joined: Apr 01, 2012
Posts: 168
Location: Zone 6a, Wahkiacus, WA
Hi Jo,

We are in south central Washington and have relatively young basalt derived clay soils, which are also very shallow. Not unlike what you described. Like all clay, it is easily compacted. and we have had to excercise our creativity to combat the systemic problem of heavy compacted soil.

My recommendation is first to go seek out other areas where there have been incidences of disturbance that resulted in similar situation. Observe what plants pioneer that space, collect seed from them and get the planted.

You will likely find that the pioneers in such situations are tap-rooted plants "flat-weeds" which are generally low growing. Things such as Mullein, Dandelion, Mallow and perhaps Thistles. You can also think to add deep rooted nitrogen fixing herbs such as alfalfa, medick, and trefoils.

An important principle, which I could even call a "constant of nature" is that the best thing to do for any soil situation is to add carbanaceous material AKA create humus. These deep rooted plants will puncture the clay, and then die and decompose. Creating channels of organic material in the soil. assiting these pioneers with a good layer of mulch can hardly hurt the situation.

You can speed this process up by stacking a lot of pioneers on your site, and running over the ground with subsoiler of some kind. That can be something as rough as the rippers on a bull dozer, or something as precise as a Yeamons plow. regardless of what you specifically use, the end result is going to be dramatically increased infiltration and aeration which will help those pioneers do their work even quicker.

Hope that helps give you some principles to work from.

Windward Intentional Community
samuel fitzgerald

Joined: Apr 03, 2014
Posts: 2
Hi all,
I'm new to the permies forums and really to permaculture in general. Although have studied it.
I have the same problem with clay in my vegetable patch. It sounds like you guys suggest organic mulch cover and just wait would be the best route? I may be only living here (sw uk) for say a year, would anyone suggest something that may be faster working? I will try the mulch regardless... May as well lay the groundwork for who ever lives here after us!
Thanks all
John Elliott

Joined: May 08, 2013
Posts: 2170
Welcome to Permies, Samuel!

If you just mulch with wood chips, that is going to take time. But if you till in the wood chips, that gets faster results. You want to do your tillage without stressing the native soil fungi though. If it is 12" down to solid clay, just set the tiller for 6". Leave untilled strips through the area you are tilling, that way soil fungi can regrow back in from the sides of the untilled strip to take advantage of all the new food you have added to the soil.

If you have access to sand or gypsum, till those in as well. The perfect soil is equal parts sand, silt, and clay, with maybe 5-10% organic matter. That's rare to come across in Nature, she always has some process going on that is pushing the soil to pure clay or pure sand and organic matter is either totally absent (desert soils) or in huge excess (peat bogs). When you know what you have, and where you want to go, it just becomes a matter of dedication to add the right soil amendments to push it in the right direction.
samuel fitzgerald

Joined: Apr 03, 2014
Posts: 2
Thanks john!

This all makes sense. I guess I'd see the best results if I hang around and wait. Regardless I'll try your suggestions and if it works for me then great, if it doesn't then the next tenants can profit from it

Time to stop moving house I think!
Rosco Heber

Joined: Feb 07, 2014
Posts: 34
Location: Arkansas Ozarks
I'm in Arkansas Ozarks with lots of clay. I dug out parts of garden each year and added many many trailer loads of mulch i get for free. I dug at least 18in keeping the top soil separate. Then put in mulch and till, more mulch and tilled. Then some of clay back in and more mulch. You get the idea. Its a lot of work and my garden is 5000 sq ft. Last year in our front yard, which had even worse soil. I dug out large holes where i was going to try growing tomatoes. Each hole got 3 or 4 large wheelbarrow loads of mulch. That worked pretty good. I've probably got over 100 pickup loads in garden but its made a fantastic difference. No one around here has soil like I do.
I figured out how much sand I would need according to what i read about clay and since I'd have to buy it paying thousands of dollars didn't make sense. I also pile extra free mulch to age, and have that when i need some.
Barry Fitzgerald

Joined: Nov 12, 2013
Posts: 40
Location: Welland, Ontario, Canada
Hi Everyone, I will share some observations and what I have tried. Sand and wood chips tilled in make the soil looser for a little while, after a few years, not so much. Horse manure and autumn leaves tilled in gave the best results and lasted for many years. Peat moss gives good results as well but it is expensive.
This is not permaculture, it is for someone that needs quick results.
I suggest you find a riding stable or horse owner and make a deal for the manure, around here people actually pay to get it taken away. There will be no guarantees that it is organic or medication free so consider that as well.
Mulch heavily to prevent the soil from drying out and cracking.
Once you have established organic matter in your soil and can actually grow something that you want, then follow the permaculture principles.
Have you seen Paul's rant on CFLs?
subject: hard clay needs rehab to make garden