Improving clay soil without disturbing the soil structure

Hi guys,

does anyone know how to improve clay soil solely adding organic matter on the surface without disturbing the soil structure? Is this even possible? Maybe adding layers of compost and grass clipping and/or wood chips ?

Sure, that's how nature does it. It does take time. Using mulch helps too. Just watch for slugs if you have them in your area. Mulch gives them a good place to live. You might want to put your location and gardening zone in your signature. Most clay soil here in the Midwest USA, is acid -- low ph so adding lime every few years to start helps. Once you're soil has been improved with organics, you might be able to quit using lime. There's also certain things you can plant that will help with drainage. Daikon Radish is probably the most widely used plant for that.

You can use a broad fork, or broad forking techniques with a regular fork, to open up spaces in your clay soil.

The main enemy of preserving the soil structure and soil life is inverting your soil strata. Don't dig down and flip over.

If you want to improve your clay, I would suggest soil samples to see what your soil lacks. Generally speaking, adding wood chips or other organic matter to the top of the soil will eventually result in soil macrobiota and microbiota coming along to help with decomposition, and better soil will result.

Using a fork to loosen your soil without inverting it is also a way to introduce a little organic matter or rock dust to your clay. Increasing the amount of woody surface area exposed to the soil usually results in some kind of nitrogen draw-down, as the bacteria digesting the wood draw what they need from your clay, but clay holds on to nutrients and minerals really well, so that may not even be an issue. Also, putting rock dust down to work its way into the air spaces in your clay will then allow the rock dust to hold open those spaces, increasing drainage and air in the soil.

Bryant Redhawk has an awesome soil primer.

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

But yes, you can also grow things to improve your clay soil. Growing green manures with a variety of root zone profiles will put organic matter into the soil, and if you chop and drop or roll down your green manures, you will also drop organic matter on top of the soil. Worms and other soil macrobiota will arrive on the scene and do their thing.

What are you intending to use your soil for, specifically? Could you tell us more about your specific situation?

-CK

Does your soil have any structure to start with? If it is compacted fill, for instance, it might be worth using mechanical means to loosen it, which will speed the process.

I'd second Chris' suggestion about a broadfork; they are really fun to use.

I have mostly clay soil at my place. Parts of it are really compacted where people used to park for example or used to have one of those round above ground swimming pools. Other areas are not compacted except during the summer the soil becomes rock hard. Depending on the area I'm trying to improve I do different things.

In the hard compacted areas I have used equipment to dig down to open it up. I also constructed several large hugel beds in these areas. While these can be built on the surface I partially buried mine. When I dug down I placed large woody debris into the hole and then added the soil back. On top of that I added smaller woody debris and then added more soil on that. But you could just stop after adding back the soil that was dug out. In my case I just wanted to improve a long strip of compacted land to make a hedgerow or living fence so this worked well for me.

In most other areas on my property I'm just adding mulch in the form of wood chips right on top of the soil. Overtime this will greatly improve the soil and I have found that it also prevents the soil from becoming rock hard in the summer heat. If there is grass or other vegetation I don't want then I place cardboard or newspaper down first and then add the wood chips.

Another thing to consider is planting tap root species such as tillage radishes that will open up the soil with their roots. If you leave them in the ground to decompose over winter you will get little pockets of rich soil.

Good luck!

Hi John, thank you for the suggestion of adding my location and gardening zone! I am in central Missouri not so far from you I guess. Thank you for your reply I will try planting Daikon Radish and other plants that can help.

Hi Chris, thank you for your suggestion of using a broad fork. I added lots of wood chips last summer and for a while I noticed strange unicellular 'stuff' and googled it and figured it's called 'dog vomits' or something like that...yuk...and that is supposed to digest woody material. I am not sure if that is a good thing or not. I will try with rock dust and thank you for Bryant Redhawk post link. I want to create a garden with perennials, flowers and vegetables.

Hi Gilbert, thank you for your answer, I am not sure I know how to answer to your question about the structure of my soil. I can tell you that the spot where I want to create a garden was completely filled with oak trees and that I got rid of something like 30-40 of them. And then I used all the wood chips to cover the soil. So I guess is a soil that has never been used for gardening and shouldn't have too much compaction since it was not possible to drive on it or things like that.

Thank you guys for being so helpful!

Hi Daron, thank you for your precious suggestions!

This won't be popular here, but what I'd do is:

Get a pickup load of sand, about a ton don't look like much in the truck, but I don't suggest hauling more, especially over rough terrain. Turn over the clay, then add some kind of vegatative matter, mulch. compost, leaves, peat moss, whatever you have or can find. Then I'd add another inch or so of composted manure. Then add on a couple inches of sand and then turn that over into the soil. Some would suggest that you could do that in one pass, but with all that matter piled on top you won't loosen up the soil as deep as doing it with out any cover.

If I were to later dig in seedlings I'd again add composted manure into the hole I dug for the seedling. I added a lot of manure two years ago into my tomato patch and the, beefsteak, tomatoes grew about 12 feet high. I didn't get a lot more tomatoes, but they were sure happy. The ones along the fence between the tomatoes and the blueberries grew up the 5 foot fence and back down the other side. Those at the fences on the edge grew over the fence and some got eaten by the deer.

I had been having problems with late blight and that year the tomatoes grew faster than the blight progressed. I outgrew the blight. Last summer I let that patch go fallow except for some early turnips and lettuce. I then planted Caliente 199 mustard. I let that go to seed and after the seed spread I dug the first crop in. I got a second crop which I also dug in just before the first frost. They don't recommend letting it go to seed, but I did. We'll see this year how much of a mustard weed problem I have.

You may need more loads of sand and mulch, compost etc., but I don't know how big a garden you're growing.

Hi John Duda,

Thank you for your answer...I read in several articles on multiple website that clay and sand are prone to make cement-like soil...not sure I want to risk that

Luigi Della Vecchia wrote:Hi guys,

does anyone know how to improve clay soil solely adding organic matter on the surface without disturbing the soil structure? Is this even possible? Maybe adding layers of compost and grass clipping and/or wood chips ?

hau Luigi, several people have given good ideas of how to improve your clay soil, all those ideas are good ones, even though they are not all about nothing but organic materials.

The best way to improve any soil type is to grow plants, the roots will break up the soil type, add exudates that call to action bacteria and fungi and after 5 to 10 years your soil will improve from nothing but growing plants.

There are many faster methods, the least damaging to your current microorganisms is use of a broad fork to open the soil from below, this fractures the horizon boundaries and that helps greatly with water infiltration, sinking in of organic materials from the surface and that increases microorganism numbers.

Use of a tractor and sub-soil plow, this is very similar to using a broad fork but faster since it is pulled by the tractor, the method is the same for both the broad fork and the sub-soiler, lay down the organic material(s) then open the soil by fracturing the horizon boundaries.

If you have a high content clay soil, you can not add sand unless you have already added quite a lot of organic materials to clump the superfine clay particles, clay + sand + water = the blend used for making pottery, it will be very concrete like as it dries (cracking at the surface, needing a pick to break it up).
John addressed this by talking about the vegetative matter. I would recommend not adding sand until you can dig the soil with a shovel easily, even when dried out for two weeks. This is the point of organic content that sand will help instead of hinder.

When you buy topsoil in this area, SW Pennsylvania, what you invariably wind up is a shredded mix of sand and clay. The better topsoil also has a little organic mix. I wouldn't buy it because I'm afraid of getting the output of the sanitation plant.

I mix my own "topsoil" by adding some sand to the clay I already have. If I'm growing annuals I want my garden to produce this year. If I'm growing a bed of perennials then I can mulch bark. wood chips, some years adding mushroom manure. In the perennial bed I have the luxury of waiting years for the soil to improve. I can let the worms bring the mulch down into  the soil. But before I plant a perennial I improve the soil immediately around the planting I'm doing.

I have an acre and a half, it's about half heavily wooded and half lawn with my house, beds, and the driveway. There are three rows of mature pines. I've been here 13 years, never bag my grass clippings, they've been blown into the lawn all those years. I suspect the previous owners did the same. Last year I opened a new tomato bed between two recently planted fruit trees. I did this to allow my old tomato garden to go fallow for a year. But I know what's in that ground, an inch or so of roots and a little topsoil. The house here was built 65 years ago, before that it's said there was farmland here. I added my sand and the compost, some peat, leafs, and manure into the sod that was there. I dug it up twice. It's much better than the clay that was there. I did that with much of old tomato garden. It's no longer clay. It's a nice loose loam.

I could built a compost pile into a spot out in the clay and maybe in 5 or 10 years I'd have a better clay mixture. But, I don't have the time. I'm 73 years old.  As it is I got a nice crop of beefsteak tomatoes, and one yellow pear. In the 13 years the work I've done hasn't created any concrete. Where did I go wrong?

hau John, you didn't go wrong, as you mentioned that land has been under some type of cultivation for quite a while, that means organic materials have been going in to the soil for that amount of time, what ever that amount of time is (must be more than the 13 years you've been there since you mentioned a previous owner).

I have an acre and a half, it's about half heavily wooded and half lawn with my house, beds, and the driveway. There are three rows of mature pines. I've been here 13 years, never bag my grass clippings, they've been blown into the lawn all those years. I suspect the previous owners did the same. :  I added my sand and the compost, some peat, leafs, and manure into the sod that was there. I dug it up twice. It's much better than the clay that was there. I did that with much of old tomato garden. It's no longer clay. It's a nice loose loam.  

That sounds to me like lots of roots, exudates, bacteria, fungi and other microorganisms have been there for a long time.
It takes 10 years to turn solid red clay into black, humus rich, top soil by planting, chopping and dropping, over and over.
Are you saying that none of this enrichment has been happening?
Lawns are great at turning clays into soils full of microorganisms and earthworms only come when the soil is full of microorganisms because that is what the earthworms eat.
(red wiggler worms eat lots of things but earthworms are different, the leaves they pull under are used to grow fungi and bacteria much like some ant colonies grow fungi for food)
Also you mention that when you dig you add more than just sand, so you are starting the clumping process which negates the ability for clay and sand to make the concrete.

I'm not really sure that you understood that I was giving you a complement, I was giving you a complement.

Redhawk

Bryant:

I saw where you said I addressed the......

I was merely arguing against the idea not to add sand to clay. It seems obvious to me. Clay is very fine textured particles of soil. Sand is a much larger particle and breaks up the clay by mixing with it.

I want to also add that I did and do all my digging with a spade. As I said I'm 73 and have a medical problem that causes fatigue. The prescription for that problem also causes fatigue. It also causes a photo sensitivity problem. So I go out with my spade, a bottle of water and a folding chair. I dig for five minutes, take a 10 minute break in the shade ponder the beauty of the world. And then get back to digging. I've found that to make the initial hole is very difficult. Once I have a hole I can keep attacking the edge, usually 2 inches at a time, sometimes only an inch. Over a number of days I get the job done. The tomato patch I did was, as I said, between two fruit tree plantings. I opened the fence around each tree making the diameter larger but kept the single post for each tree. The new fence was about 16 feet between and I dug out that patch about 10 feet deep at the widest. I got 13 tomatoes and one pepper in that patch. 7 different beefsteaks and the one yellow pear.

In my old garden I've been adding a big load of leafs, maybe a cubic yard, into an 11'x14' patch every fall for years. I throw in some veggy items from the kitchen, with some coffee grounds and egg shells. I could do a lot more than I do though. Some I feed to the deer and they green up the lawn for me.

I was just looking a couple weeks ago at the broad fork mentioned above. I'd really like one of those to go around the drip line of my fruit trees. I'd even rake in some manure into the grass there.

It also occurred to me since I posted above that the golf courses do a procedure they call Topdressing where they spread a fine layer of sand into the clay on the course. I've done that long ago. I think I put a mixture of 3 parts mushroom manure to one part of sand. The sand improves the tilth of the mixture tremendously. Keeps it from clumping. Makes a miracle mixture that spreads wonderfully. Anyway after I got done with the broad fork I'd add that mixture into the turf, maybe a half inch.

I'm not saying don't add sand to a soil in progress, I am saying don't take a pure clay and add sand first.

I used to make pottery, way back in the 1960's and early 70's. I have a terra cotta clay deposit on my farm that I plant on using in the future for making pottery.

Arkansas has areas that are nothing but clay. All the rice fields here are either red Georgia type clay or black Gumbo clay. (plowed to death every year so that any organic matter just blows away prior to planting)
I used to have to fix fields for farmers when they would try to add sand to their clay fields of 250 acres per plot. I've seen 450 hp. tractors hooked up to 6' long, 1" thick busting tine plows stopped dead in their tracks with nothing happening to the field.
I do know what I'm saying from many years experience of having to fix farmer caused field errors, and the farmers paid me lots of money to do it for them.

Bryant

I guess I never got into a situation like that. If I'm working in a garden and adding sand in then the way I think, I'm going to add something organic while I'm doing it. However I could see where I might think I'll add a little sand on the first dig and could get into trouble.

Suppose I bulldoze a new driveway thru clay and I mix in some sand. Does the concrete like mixture get hard enough that I'd have a paved driveway. Would water erode it?

Interesting conversation.

I've seen (and driven over) a drive way that was compacted pure clay and sand, it had a proper crown and that crown moved rain water off the surface fast enough that it didn't erode but if the rain was long lasting, it would start to get slickish, not slide off the road slick but slick enough to make me slow down.

I think that if you mixed the sand into the clay well then shaped it and packed it down (what the above road looked like had been done) that it would not be a big issue. If you let it dry and or it got sun baked, then I'm fairly sure it would last well.

My own road is a steep grade, red clay under SP2P gravel, rain softens the clay and my gravel is now embedded into the road base pretty deep. I have to put one more layer on it (according to the road builder) to make sure it remains stable.

At my last place the driveway was steep and it was in the natural waterway...dumb. I had to add gravel every year. They called it 3b. the 3 referred to inches, the b meant it didn't have any fines, or silt, just stones. So over the years I learned to add the gravel after we'd gotten some snow, I mean not a dusting. So it snowed I drove down and out and bought a ton of gravel. Shoveled it into the tracks, which covered the snow. If it iced up the gravel was locked in. The problem was if we got a quick thaw the water would flow down the stream bed, the driveway, and the car track was the obvious lowest spot. So it gushed down thru the track and kept going. It got so bad sometimes I thought of throwing belgian blocks, the stones they use for paving streets, into the ruts.

edited quick freeze to thaw

Let me add my Amen to several of the above suggestions:

1.  Yes, pile on the organic matter and let the earthworms and other soil biota integrate it down into the soil profile.  Wood chips are amazing.

2.  Yes, get a living root growing that will punch down into the clay and pump life into the soil.  Soil tillage radish is a great way to break through the hard pan and push biomass down into the soil.

3.  Yes, broad fork or some other way of doing subsoil break-up.  But don't break yourself doing what nature will do naturally for you if you'll just give it time.

4.  As tempting as it might be to think that you could spread some sand around and improve drainage, save your time, effort and money.  If done wrong, you'll make things worse.  At the most, experiment with a small area and see if it makes a difference, but dragging in all sorts of mineral amendments is decidedly non-permaculture (in my humble opinion).

Let me add one more idea:

5.  If there is a slope, dig swales.  It will help to catch organic material and hold it on site --- not just water, but carbon, which is the secret to turning hard clay soil into friable black garden soil.

Luigi Della Vecchia wrote:Hi John, thank you for the suggestion of adding my location and gardening zone! I am in central Missouri not so far from you I guess. Thank you for your reply I will try planting Daikon Radish and other plants that can help.

Ok so you've probably got clay and most likely rocky clay. I finally found a piece of property that isn't rocky but that's rare in the Ozarks. With little to no manual labor or machinery, it's going to take some years to improve the soil for veggies. Even with food forest items, you'll want a $200 hole for a $20 tree/bush(that's a landscaper saying), otherwise it will grow very slowly. It's not a bad thing to loosen up the upper soil once to get things off to a quick start. What you don't want to do is bring any subsoil up. I double dug my beds which is a LOT of work but it does a really good job. Dig the upper soil off with a forked spade, stick the spade down into the sub soil and rock it back and forth to crack it open, put the upper soil back in along with amendments. When I did that, I grew potatoes and had the best taters in the area and bigger harvest too. My neighbors have been at it for years but only til the soil while never adding anything except for commercial products so they still have the same clay they started with. It might have more nutrients but that only lasts one season. This was my second year on the property and they thought I was crazy for asking to rake up their grass clippings to make compost. Anywhere I've dug out here, I've found a hard pan, anywhere from 12-20 inches down. I'm not sure Daikons would even go through it. One thing about digging/cultivating clay, the timing is everything. Too dry and it's like concrete. Too wet and it sticks to your tools, plus you WILL destroy the soil structure. Those clods turn into rocks. Rain will break them down but it takes a few years. Like you, I had a lot of trees so I have to deal with roots when digging.

Sand; It would cost a small fortune to have enough to be effective, plus it needs to be coarse sand, else you're just making adobe. As someone said, there's nothing wrong with clayey soil, it just needs organic content mostly. If it's not red, red clay, it's clayey loam, silty clay, clayey silt etc. We got lucky and have clayey loam but with last year's rain and me not putting compost in it, I'm almost back to what I started with.

Your best bet for veggies might be raised beds and/or huglekultur. That way you don't have to worry about cracking open the subsoil/hardpan to get drainage. It does require bringing in some material unless you can make tons of compost. There's a place called St Louis Compost I believe and another in Seymour, MO. Both sell compost and garden soil. Also, check out Sqaure Foot Gardening You don't necessarily have to use his grid system but he has a recipe for the starting soil. After that, no input is required except for adding homemade compost and other organic materials. He's got two systems. The original calls for mixing the new materials in with 6 inches of your top soil so you end up with 12 inches of fluffiness. The new system calls for just putting the new materials on top which only gives you 6 inches of fluffiness and he claims that's all plants need. I like the original system because even our top soil is tough stuff and I think some plants need more than 6 inches.

You may or may not know but you're not far from the George O White State Nursery. It's in Licking and you can get food forest seedlings and other stuff for $0.40 each. All MO native stuff so you know it will grow here. They start taking orders in Sept and the edibles sell out quickly. They used to have a good selection of legumes aka nitrogen fixers but they don't anymore or at least didn't this season. I think it might be that some of them are considered invasive species. I planted 150 bushes along the edge of the property on the gravel road side for privacy and dust blocker this past spring but they haven't grown much because I didn't do 150 - $200 holes.

There's no shortage of sawdust out here. Just need to find a mill that doesn't charge for it. Look for the ones with the biggest piles that don't change much. We use the bucket toilet system aka humanure but I don't use it on food items yet as I need to get some compost thermometers and even then, I don't know if I could bring myself to do it. We use it on flowers and I put it around the dogwoods. I did have a volunteer tomato plant pop up in a pile this past year. Big beautiful plant and mates but I just couldn't bring myself to eating poop maters. Maybe if I knew it had gotten over 140 degrees. I also use it for chicken bedding and then mix even more of it in with what I clean out of the chicken housing.

You've got lots of leaves that can be made into leaf mold. Slow process but very low labor input and it's good stuff. If you've got wild blueberries and less so, wild blackberries growing, you've probably got low ph aka acid soil so some lime will help with certain things. Don't use it for potatoes and use very little on tomatoes. You can get a general idea of what your soil is here https://websoilsurvey.sc.egov.usda.gov/App/WebSoilSurvey.aspx It's been years since I used it so I can't tell you how it works but it will give you the classification of your soil, description eg clayey loam, ph level, grade etc as a downloadable report. Since we have blueberries, it was no surprise that they said a ph level of 4.5 - 5.2. Somewhat well drained for part of the property and somewhat excessively drained for the rest was a surprise though and I tend to disagree with the somewhat well drained part due to my hard pan. I dug some 2 foot deep holes for poles and they filled up with water and kept water in them for two weeks with no rain. The somewhat excessively drained, I agree with as the soil is almost white. Any organics have been rinsed right through. Luckily that's a small portion and there must be some kind of nutrients down there because some things do grow. One of these days I'm going to get a soil test done. Not cheap here for some reason.

Potted plants, raised beds for as much as you can is about the lowest labor input. I fight back the weeds and grass every year with my non raised beds. Once clayey soil gets dry, you can't even pull weeds. Mulch helps a lot but takes quite a bit of work too and you need something for mulch. When/if I have plenty of compost, I mulch with it. A lot of nitrogen is lost to the air though.  

They always say to add compost to alleviate almost every soil problem.  My plan of attack for clay hard pan would be to dump some playground sand that you can get at the box store.  Then I would start planting driller oil Radish, Tillage "Raphanus sativus var. niger" or "Minowase Radish"  "Diakon radish Raphanus sati var. longipinnatus"
these three will drill into most soils deep.  They are planted before fall since they winter kill.  Then you could next plant winter rye.  Cut it down in spring before flowering.  After these steps the soil should be on it's way to loam.