10 inches of compost on top of clay. Should I till it in?

The pics below are composted wood chips that were put down 2 plus years ago. Also pictured is the compacted clay.  Zone 8 Central Mississippi...

We started by cutting down pine and oak trees to open this area up for a veggie garden and orchard.  We cut the stumps off even with the ground and then mulched with ground tree litter from a local tree cutter to a depth of 14 to 16 inches.  On top of this we sifted 4 inches of compost on top to create  30" beds and planted directly into it.  This worked well for fall,  winter,  and spring plantings but was nearly impossible to keep most in the summer.  Drainage was too good.

What we ended up with after 2 years is 10" of finished compost on top of clay that is still compacted and separated from the compost by a thin layer of top soil. The clay is now moist and could be worked with a broadfork but is definitely compacted.

Should I just broadfork the area and let it be?  Or should I try to incorporate some or all the compost into the clay.  I am ordering a 14" and a 16" broadfork from meadow creatures tomorrow for me and a friend to share.

I am not opposed to a one time till after broadforking the area if incorporating some of the clay into the compost will speed thinks up and not hurt long term efforts.  When clods of clay get into the wood chips the worms turn it into topsoil with in a couple of months but it remains as clay when it is compacted.  For what it's worth,  the area is about 3000 square ft.

I dont know. But I love the soil you have built!
Maybe try multiple ways.
Till a patch. Broadfork a row. Tillage radish on a bit of it.
Double dig in spots.
The high drainage is surprising,I thought of that as a sandy soil problem. Maybe the water is hitting the wet clay and then moving sideways to a low point?
Breaking the clay/compost barrier with deeper roots seem like a good idea no matter what.
Alfalfa is deep rooted and a nitrogen fixer.

In Austrlai we have a farmers seed mix which has deep rooted radish and other stuff that loves the go down, it is then mulched at the end of the growing seson to add to the soil.
If I can get the name I will put it up here.
I plan to use it to simply let nature do the 'hard yards' as we say here.

Here's my take. I think some gentle broad forking is the way to go. With light broad fork work, with the tines entering the clay and some short pulls on the handle, it will lift and "crack" the clay below, which will aid in water draining and also allow some of that beautiful compost you have to work it's way into the cracks or fissures. I'm wondering if the clay left as is will act like a hardpan and seriously impede water drainage. Cracking and loosening the clay ought to improve this. It might be fun to to part of it lightly broad forked, and then part of it heavily broad forked, and by that I mean bring pieces of clay up to the surface with the fork.

I think using a rototiller may be a bad idea, if it will go deep enough to get into the clay, could cause a plowpan. That rapid rotation of the tiller "fingers" will repeatedly contact the same level of clay thus smoothing it over like a masons trowel on wet cement or like a plow can sometimes do, and this will almost always cause poor water drainage, which can sometimes have a host of other issues accompany it like waterlogged soil, lack of oxygen in the soil, or in a worst case scenario anaerobic conditions.

I am with William, John, and James on this one.

You have enough good earth atop the clay that you can start green manures to do your work for you, so that's almost a given.

I second the tillage or other large daikon radish seeding, and/or perhaps some mangelwurtzel beets, which, if you aren't familiar with them, are giant and do largely the same thing as tillage radishes.

I love the idea of alfalfa, because of the hosting of nitrogen-fixing bacteria and the length of the taproot, and its ability to punch down through compacted clay. I also love the idea of alfalfa in a pasture setting, because of its perennial nature. This might not be what you're looking for, but I haven't heard of it being invasive, either.

I agree with the broad forking measure, as well, especially because you are already getting a broad fork. I think that cracking that compacted clay layer a bit will give those deeper-rooted plants an easier go of breaking it up. Incidentally, if you find carrots growing really well, they could probably take up the torch in the second or third succession.

As you are broad forking, I would suggest you look at your soil test (and if you don't have one yet, guess what I will suggest next). I would suggest you decide the direction in which your soil will need to be amended, select the appropriate rock dust, and put that stuff down beforehand. Rock dust will sift down into the cracks you will make in the compacted clay, holding them open for better water, organic matter and root infiltration.

Also, Bryant Redhawk has a couple of threads that deal with soil. If you haven't read through them, I suggest you do.

https://permies.com/t/63914/Soil
https://permies.com/t/67969/quest-super-soil

Good luck, and please keep us posted.

-CK

A little clarification.  The previous owner kept the ground swept clean so no leaf litter was allowed to stay.  The clay was like concrete.  I started out trying to double dig but after 2 hours I had a total of 32 square feet properly prepared.  I gave up as I was looking at 1/3 an acre. I deep mulched and placed the beds as close to on contour as possible.  Each beds are 30 inches wide and 40 feet long yielding 100 square ft each.  

The whole thing is on a sight slope.  When it rains, the water quickly passes through the compost to the clay layer. From there it moves off to the yard. The clay is softer now and moist but the rain still runs off.

I have planted lots of turnips, mustard,  and other crops with long trap roots.  When they reach the clay,  they turn sideways and grow parallel with the clay but they do not penetrate it.

All of these things combined cause most of the rain to be lost. We receive about 50 inches of rain a year here. Heavy watering is still required if you are to grow a summer crop.

In your case, it sounds like broad forking is probably the way to go. With that much beautiful soil on the top, if you incorporate it into the soil underneath, you should only have to do it once and then your crops and the worms and other soil life will do the rest.

Hey Greg, you just mentioned the clay was like concrete. That's a good indicator of a lack of calcium. Believe it or not, clay soils, with enough calcium in them, will almost magically loosen up and crumble. Gypsum is a great way to add calcium to a soil that won't alter the soils pH.

Others have already mentioned tillage radishes. The root penetrates deep and when the winter kills the radish it breaks down forming channels into the soil. As a low effort/high reward activity it looks well worth trying. Otherwise perhaps just give it a few years and see what the roots and earthworms do for you.

Our garden here in the UK is on chalk, but the woods we own a few miles away are on clay. And when I say clay, I'm talking a a massive bed of it about 50m deep. Building soil in those woods is about adding organic material above. No amount of digging or broadforking will facilitate drainage through a layer like that.

Looks like you are ahead of us with the tillage radishes,and it sounds like you could use  some deep infiltration basins, or perhaps a pond.
I would definitely want a pond,to collect the otherwise escaping water. It sounds like any depresion you dig,will be a pond,no worried about gleying!
You would then at least capture it,plus whatever nutrients where going with it.
Moving that water back uphill would feel like a terrible waste of time,so how about growing duckweed,hyacinths,cat tails etc,and moving the water in the form of biomass mulch?
With a pond you could grow also on  chimpapass.
The deep basins could be meters deep and filled with biomass,or maybe sea shells
Maybe dig that pit in the way of the escaping waters,then plant willow,alfalfa,rice or catails in the pit itself.
If its sitting in water, would willow still grow deep roots?
How about the other plants?
Maybe put meter wide,deep as possible ponds at the low end of each bed, collect the water, grow water loving plants fir food(cress?) or biomass,move the water back onto the nearby bed,rinse and repeat.


addendum: In the process of finding out where you live, i noticed from the threads you have started that you already have a pond!
So my contributions, helpful,maybe not so much😏

Following up on green manures etc
webpage

It sounds like your issue is retaining moisture in the topsoil. Are you using any kind of mulch over it? Shredded leaves do wonders at retaining moisture, I've used straw over our sandy loam here in Michigan with good results too.

Leonard Burdek Iii wrote:It sounds like your issue is retaining moisture in the topsoil. Are you using any kind of mulch over it? Shredded leaves do wonders at retaining moisture, I've used straw over our sandy loam here in Michigan witho good results too.

16 inches of mulch to start with.  Water drains through it.  Soil compaction is the problem.

John C Daley wrote:Following up on green manures etc
webpage

There has been crops planted in it in succession for two years.  Roots will not penetrate the compacted soil.  When they reach it they turn and grow paralleled to it.

Right, you're growing in the mulch, not the subsoil. My thinking is to mulch the broken down mulch you're growing in.

Leonard Burdek Iii wrote:Right, you're growing in the mulch, not the subsoil. My thinking is to mulch the broken down mulch you're growing in.

My thoughts exactly. Why waste all that effort taking perfectly good soil, damaging the microbiome, and mixing it with the subsoil?

Sure, you have the makings of a hard pan because of how clay behaves, but digging in your topsoil will simply move the hard pan deeper. I think your better off continuing to lay down organic matter. Rolls of baled hay for example, and put your worms to work for you.

Yeah, based on what you're telling us, broad forking is still probably the best answer. From what you describe of the actions of the worms on clods of clay you bring up to the top layer, that by itself will probably work.

Mulching your already substantial organic layer might help, but it's probably not the most effective way. You could use, for instance, a layer of green chop and drop atop it, which would temporarily trap moisture. Until it dries up itself, and you're left with yet more organic matter.

I don't think the answer to a top layer heavy in organic matter sitting atop compacted clay is more organic matter. I think regular compost extract applications would be more useful, but still probably not the first tool I would turn to in the permaculture toolbox. That would be the broad fork we mentioned.

I would be wary of using a plow or rototiller for the reasons mentioned above, the smoothing that could occur, only worsening your compaction issues.

I would probably dust the surface of your soil with gypsum and broad fork it all. When the gypsum hits the cracks in the clay, things will likely improve markedly, and then the green manure techniques you've already tried will gain some purchase.

And I like William's suggestion of using aquatic plants for organic matter, but that is clearly not what you're lacking. Likewise, I love the idea of chinampas, but only if they work for your system. Do you keep waterfowl?

I was just wondering, how much does wind play into the drying out in the summer? If it's dessication borne of dry summer winds, perhaps what you should also consider is a shelter belt of some kind on your windward edge.

-CK

Greg B Smith wrote:A little clarification.  The previous owner kept the ground swept clean so no leaf litter was allowed to stay.  The clay was like concrete.  I started out trying to double dig but after 2 hours I had a total of 32 square feet properly prepared.  I gave up as I was looking at 1/3 an acre. I deep mulched and placed the beds as close to on contour as possible.  Each beds are 30 inches wide and 40 feet long yielding 100 square ft each.  

The whole thing is on a sight slope.  When it rains, the water quickly passes through the compost to the clay layer. From there it moves off to the yard. The clay is softer now and moist but the rain still runs off.

I have planted lots of turnips, mustard,  and other crops with long trap roots.  When they reach the clay,  they turn sideways and grow parallel with the clay but they do not penetrate it.

All of these things combined cause most of the rain to be lost. We receive about 50 inches of rain a year here. Heavy watering is still required if you are to grow a summer crop.

Every one of the ideas that others have presented are good ones, I want to say that first because I am going to give you some ideas of how to attack this issue of a compact clay subsoil that will open it up within 6 months and it will only get better from there.

Since we know from your description that you have a barrier layer of clay, it will need to be cracked, the devices designed to do this are:
Broad fork, key line plow, sub soil plow, they all do pretty much the same thing, open the soil for water and air infiltration, the first one is people powered the others need a tractor to pull them. (Notice I didn't mention a Tiller! We grow soil not kill it.)
Your idea of planting deep root plants is really good except for the fact that you are not going to get through that barrier layer with them, as you found out, the roots will turn and follow the top of the barrier horizon layer.
Gypsum (powdered or small chunks), or AG Lime, are going to be your best friend when breaking a clay barrier layer, you want to get this amendment down to the clay, so spread it and then use the tool above of your choice to open channels for the amendment to travel down through.
Don't hold back on the Gypsum if you use that, soils can take almost as much as you want to apply, Gypsum is calcium so you are doing two things with one application without jumping your pH much, this is a good thing, pH adjusting should be done once you have that barrier broken up.
Gypsum is also long lasting where AG Lime is only good for a year or two. Severe cases do benefit from using AG Lime first then coming back with a Gypsum amendment, both times you open up the soil so they can sink in.

Once you have that barrier layer cracked open, your plants will thrive with deep roots doing more organic injections for you.

Redhawk

Bryant RedHawk wrote:

Greg B Smith wrote:A little clarification.  The previous owner kept the ground swept clean so no leaf litter was allowed to stay.  The clay was like concrete.  I started out trying to double dig but after 2 hours I had a total of 32 square feet properly prepared.  I gave up as I was looking at 1/3 an acre. I deep mulched and placed the beds as close to on contour as possible.  Each beds are 30 inches wide and 40 feet long yielding 100 square ft each.  

The whole thing is on a sight slope.  When it rains, the water quickly passes through the compost to the clay layer. From there it moves off to the yard. The clay is softer now and moist but the rain still runs off.

I have planted lots of turnips, mustard,  and other crops with long trap roots.  When they reach the clay,  they turn sideways and grow parallel with the clay but they do not penetrate it.

All of these things combined cause most of the rain to be lost. We receive about 50 inches of rain a year here. Heavy watering is still required if you are to grow a summer crop.

Every one of the ideas that others have presented are good ones, I want to say that first because I am going to give you some ideas of how to attack this issue of a compact clay subsoil that will open it up within 6 months and it will only get better from there.

Since we know from your description that you have a barrier layer of clay, it will need to be cracked, the devices designed to do this are:
Broad fork, key line plow, sub soil plow, they all do pretty much the same thing, open the soil for water and air infiltration, the first one is people powered the others need a tractor to pull them. (Notice I didn't mention a Tiller! We grow soil not kill it.)
Your idea of planting deep root plants is really good except for the fact that you are not going to get through that barrier layer with them, as you found out, the roots will turn and follow the top of the barrier horizon layer.
Gypsum (powdered or small chunks), or AG Lime, are going to be your best friend when breaking a clay barrier layer, you want to get this amendment down to the clay, so spread it and then use the tool above of your choice to open channels for the amendment to travel down through.
Don't hold back on the Gypsum if you use that, soils can take almost as much as you want to apply, Gypsum is calcium so you are doing two things with one application without jumping your pH much, this is a good thing, pH adjusting should be done once you have that barrier broken up.
Gypsum is also long lasting where AG Lime is only good for a year or two. Severe cases do benefit from using AG Lime first then coming back with a Gypsum amendment, both times you open up the soil so they can sink in.

Once you have that barrier layer cracked open, your plants will thrive with deep roots doing more organic injections for you.

Redhawk

How much gyp to apply?  I can get powdered in 50 lb bags. The ph of the soil is about 5. The compost is 7. I thought gypsum was used to lower ph? And lime to raise? I have a good bit of wood ash stored also I could add.  Lime is easy to get in bulk here.

The clay layer is very deep.  I don't know how deep but at least 4 feet as that is as far as I have dug in one spot.

Should I move the compost to the side and fracture the clay as deep as possible adding the gyp to the clay only?Then placing the compost back on top? I could then fork it all again and incorporate some of the compost into the top few inches of the clay leaving thick layer of compost on top?  What say you?

First of all, WOW!  What you've got in 2 years is pretty amazing.  My hunch is that you are decompacting that sub-soil much more than you are aware of.  There have to be a lot of worms and fungi in all that biomass, down there doing their thing.

I'm all for tillage radish, but I've found in my heavy clay soil that they tend to only go down so far before they start to push the top of the radish out of the ground.  You end up with half or more of the radish growing upwards rather than punching down into the soil.  I still add radish seed in with my cool season cover crop mix -- it's better than nothing.  But I've found a couple of plants that punch through clay much more aggressively than radish.

The first is fennel.  It's tougher than nails and grows really well in clay.  But if you get out there and try to pull it out of the ground, it's like pulling an oak tree out.  Fennel acts like a drill.  I've never seen anything so good at punching through the hard clay soil.

The second is a weed that grows here in Southern California:  Little Mallow (sometimes called Cheeseweed).  Like fennel, I find the tough roots tend to drill down through even the toughest soils.  My hunch is that any mallow would do so.

We eat some of that fennel and I will throw a bit of the fennel frond on fish when I grill it.  I got the original seed from a grocery store --- just the fennel seed in the little jars in the spice section.  Once the plant is established, good luck trying to yank it out.  But to kill the plant, I just hack it back to ground level with a shovel or other tool.  As a bio-mass producer and a soil driller, you can't beat it.

Best of luck.

I live smack dab in the middle of the Berkshires and in my adventures to find a little piece of land to call home I've looked at a lot of places in eastern New York. Rensselaer and Columbia Counties.

The general landscape is a valley with the Taconic Mountain Range to the East and the Hudson River to the West. From my research, waaaaaaay back when, a glacier moved through the valley and compacted a layer of soil that's anywhere from soil surface level to 25"-ish inches deep.

This compacted layer of soil is known as a "fragipan" and basically nothing can move through it. Not tree roots, not water. The freeze-thaw cycle doesn't break it up. Often the soil on top of it is fertile (in the various ways soils around here can be fertile). The main issue is that water during late winter/spring thaw will "pond" on top of the fragipan (and around here that means potentially major leach field issues).

I don't own a plow or tractor and often I was looking at plots of land around 5 acres. For me human powered tools were insufficient. I'm came across a number of studies researching how to break up fragipans, as this kind of soil layer is also an issue in place throughout the Great Plains. Scientist found that Annual Rye Grass (Lolium multiflorum) roots exuded a compound that broke up the fragipan, allowing their roots to grow into it. Crops planted afterwards would follow the pathways created by the Rye Grass roots.
Here's a link; https://www.hindawi.com/journals/tswj/2014/276892/

Not having purchased a piece of land I never got to test the fragipan layer and see what elements it was missing, but like others have said, I have read that calcium is effective in remediating the tilth of compacted clay soils.

Two questions.  

Should I move the compost,  apply the gypsum to the clay before forking, then replacing the compost on top?

How much gypsum to use?

I would simply apply about 1 lb. of gypsum per foot and fork the whole thing into the clay so you are also giving the humus a chance to get right down into the clay with the gypsum.
With it all intermingled the improvement will move along much faster and the microorganisms will have many places to inhabit and multiply.
This will give you richer soil that is on the way to becoming full of life right away.

Redhawk

Thank y'all very much!  I will be starting another thread about a similar situation with fruit trees.  It will have pics of incredible success and some failures.  I need some advice on it also.  

I got the broadforks in and started working on the garden today.  The meadow creatures forks are Beast.  A friend and i ordered one each of the 14 and 16 inch forks.  

You guys were right. The clay under the compost was breaking down.   The first 4 to 5 inches of clay was really crumbly and not nearly as sticky as when I started this project.  Most of the roots and small stump have broken down also.  All that is left is the big stumps under the compost.

Due to the clay starting to break down i used 1000 lbs of gypsum and 150 lbs of lime per 1500 ft. I can always add more gyp if needed.  

Next time we fork it should be easy.  Here are a few pics.  

I'm so glad you are getting good results!
This thread has helped me, thanks for sharing.

Greg B Smith wrote: The pics below are composted wood chips that were put down 2 plus years ago. Also pictured is the compacted clay.  Zone 8 Central Mississippi...

I know it's a long shot but is there an update to this situation? I am in almost the exact situation, north central MS, at least 4 ft of clay, and I've been working on a solid layer of organic on top. The area had zero top soil when I moved here. I've now got about 7 inches of leaf and crass clippings that have been breaking down for a year or two, and it seems like this year things are growing well enough in it..

There is still a very obvious divide between clay and organic, and I don't know if it is worth fighting or not. I feel like "punching through" the clay would be an excercise in futility due to the depth, and I wonder if my best bet is to just bring in some soil to mix in and just garden on top of the clay? Or just keep waiting as the crawdads and fireants keep bringing up mounds of clay into the compost.

B Permie wrote:

Greg B Smith wrote: The pics below are composted wood chips that were put down 2 plus years ago. Also pictured is the compacted clay.  Zone 8 Central Mississippi...

I know it's a long shot but is there an update to this situation? I am in almost the exact situation, north central MS, at least 4 ft of clay, and I've been working on a solid layer of organic on top. The area had zero top soil when I moved here. I've now got about 7 inches of leaf and crass clippings that have been breaking down for a year or two, and it seems like this year things are growing well enough in it..

There is still a very obvious divide between clay and organic, and I don't know if it is worth fighting or not. I feel like "punching through" the clay would be an excercise in futility due to the depth, and I wonder if my best bet is to just bring in some soil to mix in and just garden on top of the clay? Or just keep waiting as the crawdads and fireants keep bringing up mounds of clay into the compost.

I live on top of clay as well

Clays do not generally have a problem with fertility and organic matter - both of which they are rich in. The problem with clay is density, aeration and waterlogging. Adding organic compost on top of clay is in my humble opinion not necessary. What is necessary is to grow deep rooted plants (long term) / cover crops and in the interim - broadforking. It is OK to plow/till the clay ONCE - to bust it up and start the process of no-till growing the soil upwards - but long term you want root penetration by perennials. Clovers, docks dandelions etc. - are all perennials with deep roots that bust up / aerate the soil - mow them short, cover them with plastic (OK to do once just like plowing) or cardboard or thick straw/old hay and plant straight into it - the soil underneath is likely to be not so compacted. On the "short growth cycle" side to combat compaction - radishes (daikons) and various cover crop mixes that contain them. Working clay is a multi-year process (just like working sand) but IMHO "enriching" clay with more organic matter is like wearing a sweater on top of a jacket... IMHO a lot of people get on the "compost train" and that's OK but what you can also do is smart rotation of plots with cover crops grown year round in some of them while others are producing - and smartly terminating said cover crops or simply letting them die off naturally. For example, buckwheat does not survive cold weather so it is an ideal summer cover crop to scavenge phosphorus into the soil for the next crop - which could be wheat mixed with clover and trefoil (which will scavenge nitrogen) - followed by sunflowers after wheat harvest (sunflowers scavenge nutrients from deeper in the soil), followed by a period of 1-year long cover crop rest for the same plot.

p.s. the straw from your wheat harvest can be re-used as mulch, sunflower stalks can be used to build a honeybee hive box etc. etc.