Heavy Clay Soil Help

I wanted to ask for some advice on gardening with heavy clay and get see if anyone who has experience in working with heavy clay can be of help.

This situation: 500 sq meters of gardening space, that's going to double this year. The soil goes from jello to concrete in about 2 weeks if there's no rain. We have very little irrigation: a 2000 liter pond that fills when it rains, 6 thousand-liter tanks with 10 - 120 liter barrels attached to drip irrigation. The site has very little shade and where there is shade we're not cultivating anything. We're trying to do no-till, synergistic gardening and getting self-fertility back.

The Jello to Concrete effect: after heavy rains the soil becomes Jello, after periods of drought the soil becomes concrete. There is a window of about 10 days when the conditions in the soil seem to favor good root growth. Currently we are a droughty period. There was a little rain recently, but not enough to fill the pond even.

Things we have tried:

1. Five small in-ground hugelkultures and two above hugelkultures.
*In ground: still have the problem of drying out and becoming concrete. The Jello effect is somewhat moderated and I'm able to get Daikons in the ground. For the most part they are doing well, but I wouldn't know unless I dig down into them, and they are too small for that.

*Above ground: They are in their first year or year+half, so the jury is still out on how they will preform. They are vegeated right now with cover crops mostly, some potatoes, tomatoes, and squash.

2. A hot-bed with manure, placed in October, seeded in april.
*Good results, the tomatoes are much better than anywhere we transplanted and I'm reasonably sure that the soil situation is better there. Could be because they came from seed, but I'm amazed that they fared so well in a place where everyone buys tomato plants from a nursery.

3. Daikons everywhere.
*Not so great results here. There seems to be a catch 22 to heavy clay: taproots can give you softer soil, but you need something like soft soil to get the taproots down in the first place. Rumex, thistle, dandelion, and plantain all seem to thrive much better than daikons, and they just show up. Plus the number of daikons you have to sow and the fact that you can't eat them just breaks my heart.

4. Seeing wild seeds with taproots.
*Not much luck here. Maybe the timing was off or they weren't in the right place. Planted rumex, dandelion, and platango and didn't get much coming up. Perhaps they should have been planted more densely and in the beds.

5. Close plantings
*Seems to work well, but the plants seem to grow slowly which could be due to weather factors but could also be due to the Jello to Concrete factor, or just our general lack of water.

5. Spot composting.
*We don't have access to enough compost to make a huge effect on 500 meters, but in the spots we have used even garden waste mounded up the results have been good. We now have a big bin where we're getting more aggressive about composting kitchen and garden scraps.

6. Leaving roots in the ground
*Decent results here, but we can't seem to get enough roots roots into the ground, or perhaps they just aren't deep enough to make a huge difference.

7. Increasing shade
*Just planted a biomass, n-fixing vine (wisteria) and comfrey in large quantities. Hopefully these and other plants as they become available will increase the total shade in the area, creating a better microclimate generally and halting evaporation in the soil.

8. Heavy mulching with Straw/hay
*Impossible to seed into this stuff and eventually it compacts and the soil remains compacted as well. A strategy that favors transplants. Potential potassium build-up in the soil.

9. Planting a mixed cover crop then transplanting into that. It seems to have beneficial effects, but the soil there was just piled up, so there's a lot of air in that bed. Not so in almost every other bed.

Strategies that we're considering

1. Spiking the soil with 1-2 cm wide/10 cm long tree branches and covering that with manure.
*An extension of the november drop&plop and april seeding, but this time with wood being spiked into the soil beforehand. With the addition of mycorrhizal funghi it could have the effect of breaking up that sub soil in selected spaces and keeping the soil from compacting.

2. Different cover cropping.
Perhaps we need to do salsify or something on a bigger scale. Our land favors asters, so that might actually work. We've added some but maybe it wasn't enough.

3. Potatoes, sweet potatoes, and yacons (which may not work in our climate)
We have been hesitant to put these into the beds, but if we keep them as a soil improver, perhaps it would be okay to just let them die in the soil and harvest a few now and then.

4. Increasing enormously (haven't figured out how) the quantity of compost we create. We could perhaps get a few more families who eat organic food to give us their waste. We could also find a organic grocery and see if they'll let us compost their waste. It might be a big undertaking, going to the people and getting their stuff, but it might be worth it.

5. Make more friends among the weeds: I just found out that cinquefoil is medicine, both the leaves and the roots. Should have a go at finding a way to produce that and gain some benefit from our weeding.

If someone has any ideas on what I'm doing wrong or what I should concentrate on, it would be of help.
Thanks,
William

PS: My very first Mullein showed itself today (at 80cm tall) and that made me sooooo happy. I've been after this plant for at least 2 years and to see it in the garden was a delight.

As far as I know the solution to clay and the solution to sand is the same thing....organic matter in prodigious quantities. If supply is limited focus it on the areas you plant. I think you already have realized this with your composts, cover crops, hugelkultur, etc.... Over millennia as trees and other plants grow and break down an organic topsoil forms, but erosive processes like logging, overgrazing, and mainstream farming have caused the topsoil to simply vanish over much of the landscape. Encouraging permanent vegetation, especially trees, is the long-term answer.
A particular warning about planting trees in clay.....do not put compost or other amendments down in the planting hole!! This seems counterintuitive, but you want to backfill around the roots with unamended clay. If you put loose fluffy stuff down there, all that pore space will fill with water in wet seasons and, because it cannot soak into the surrounding packed clay fast enough, the young tree will drown. With especially sensitive species (including many fruit trees), I've learned the hard way to plant them up on shallow mounds or in small edged raised beds. These may settle back level after a few years but by then the tree will be established enough that it won't be an issue. Soil amendments are applied to the surface as a mulch...

Clay is negatively charged. You can add calcium and potassium in order to balance the PH. Organic matter will help but if you really want to fix it up add sand, redish sand is best.
If your tilling clay you must wait until the soil is dry enough otherwise it will clump up and be useless.

If there is one thing that I have learned from all my agricultural endeavors it is don't fool around with anything but good soil if the soil is no good put good soil on top or forget it. The ideal ratio of clay is 4%-7%. If you add to the soil be sure not to mix the clay in too much. Try to build new soil on top not make the clay into good soil because it will never happen.

There are however some crops that thrive in clay and if you are growing in clay than I would recommend using only thous crops known to do well in it

My soil seems the same as yours around where the new barns were built and the new pond was dug. But I had the great fortune of having cattle that I fed on those spots so they dropped lots of manure there and trampled in lots of organic matter. Some areas are still recovering but much of it is already covered with lush green growth of grasses and weeds. I let whatever wants to grow there go and get its roots as deep as it can to help break up the compaction for now, I'll not focus on getting what I want there until the weeds are lush and thick. Some areas I've already been able to mow, the plants came in so thick. I kept spreading old straw on it, and also seeds. The clover will start to grow then when it dries out just stop growing and wait until the next rain then grow a little bit more. Once it can get its roots past the hard, dry, cement-like surface, the clay holds moisture below and the clover really takes off and starts looking pretty good. Then the other plants are able to thrive as well.

I think clay is wonderful for gardening as long as you follow a few cardinal rules -
1) never let it sit bare - always keep it either covered with plants or covered with mulch, and
2) never till it - it breaks up the filaments that hold air space in the soil, which allows the roots to grow and allows air in to the roots
3) avoid walking on it when it's wet - use paths because you don't want to destroy the vital air pockets in the soil.

I think if you apply a heavy mulch around whatever you can manage to grow, that will feed soil organisms and attract earthworms and they will begin the work of opening up the compacted clay so the air and roots can penetrate.

Ask your local coffee shops for their coffee grounds. Earthworms love it and you can just dump it straight onto the ground and let it do its thing. It wont strink while its composting and looks just like dirt so wont be unsightly either. Most espresso places go through about 5-10kgs a day so if you take all they've got you'll cover vast quantities of your yard in no time. I've got clay soil and just prefer to build hugels on top of the existing soil. I start with a lyer of lgs and twigs, cover with huge amounts of greens, then a layer of manure and a layer of leaf litter. Let it sit for a couple of weeks, then toss some compost on top in a 3" layer and plant seeds directly into it. So far, so good.

The first thing you are considering is fine, but don't be so timid. A 1cm stick that is 10cm long isn't going to do much. I use a garden hose with a high pressure nozzle to ream out a hole in the clay maybe 5cm in diameter and at least 40cm deep, a whole meter if I don't hit any obstacles. You know the hole is going well when the return water looks like pottery slip -- lots of entrained clay coming up. Large rotting branches, biochar, chipped mulch, I tamp them down into the hole with a cylindrical grade stake. Try doing this every meter around the drip line of your trees, and I think you will see a big difference.

As mentioned: biochar. It's used in rain-forest soils which typically are clay albeit nutrient poor clay. I don't have personal experience on this matter but I've heard good.

I have/had the same type of soil. Moringa and pigeon pea shade it a bit as I load it up with fermented mulch/compost (Bokashi) of any material I can find.

Thanks everyone for the replies.

@Jeffrey
Clay + Sand sounds like a perfect recipe for building cement. Good idea about calcium+potassium. I think I have potassium covered, since I'm adding huge amounts of straw. Calcium is a little harder, I'm letting all my dandelions grow and set seed. Hopefully they're bringing up calcium. Plus the comfrey should help with calcium once it gets going. Interesting idea of putting good soil on top, but I think I'm stuck with what I have, since good soil costs a lot.

@Clara
Good idea about coffee grounds. I did that once, but I noticed that every time I went to ask for the coffee, I ended up having a coffee, which meant spending 1 euro for a bag of coffee grounds. I should try and get in contact with a person who works at a bar, so I don't have to do that again. In the USA they have coffee grounds at the door of places like Starbux for the taking, here that trend hasn't caught on. Even the bar where I used to get it said that gardeners would frequently raid his garbage for the coffee grounds.

@John
I like the idea of upping the diameter/length of the wood. I am a little worried that it won't rot down fast enough and I'll have too much un-rotted wood down there in the spring. I was planning on doing many stakings in a 1 meter square, like 50 sticks, so the total wood in the ground would be pretty high.

@Kai/John
I like the idea of biochar, but wouldn't it change the PH. I already have acid soil, so I was specifically avoiding things that could modify PH too much, preferring to ameliorate the PH problem with compost or more dying plant roots. Maybe I could do some test spots and see if it works.

@Alder
Trees are the answer for me too, and in this site in particular. Shade and microclimate in general would help things immensely. Thanks for the tip about backfill, I also read that in Edible Forest Gardens. Now I know the reason why you don't backfill with OM.

@Erich
Good idea about the pigion pea. Seems to be similar to Fava beans which we do grow and they do provide some shade. Confused about Moringa. Is that a tropical tree? Don't know if it will work in my cool Mediterranean climate.

ThanksThanksThanks.
William

@John
I like the idea of upping the diameter/length of the wood. I am a little worried that it won't rot down fast enough and I'll have too much un-rotted wood down there in the spring. I was planning on doing many stakings in a 1 meter square, like 50 sticks, so the total wood in the ground would be pretty high.

Well, that's kind of the point, getting big enough pieces so that they don't rot down in one season and you have to do it all over again next year. If there was a fire hydrant close by and I could do my method with a 3" diameter fire hose, then I could shove in logs that would continue feeding the soil for a LONG time. If your ground doesn't freeze in the winter, then decomposition takes place all year long (although faster in summer than in winter) and you will be surprised at how quickly buried wood will rot.

Hi William,
I share the challenges of heavy clay. Here are a couple suggestions that have worked wonders for me-

-Get a good Albrecht soil test. Mine showed excessive magnesium, which gives clay soil that impossibly sticky texture. The solution was sulfur and gypsum, which drove out the magnesium from the soil solution, freeing up calcuim to take its place. The result, which took several years to fully manifest, is a much less sticky and dense soil texture. Calcium levels were always technically good, but with the excess of magnesium ions, the calcium wasnt adequately available to the plants. The cost of the ammendments is very small, as sulfur and gypsum are super cheap. The soil test is worth every last penny to know what is really going on.

-Biodynamics. The Pfeifer field spray is the quickest route to results IME. The Biodynamic preps affect your soil structure profoundly. The soil will be more crumbly, which is such a good thing. All compost is good, but BD compost/preps will create a microscopic soil biome that is optimal for plant growth.

-Top dressing of woody compost. I used sawdust well composted with poultry manure. The slightly granular texture of this compost is really good. Simply mulching, IMHE, just kept the soil wet and heavy. Granular compost allowed the soil to transpire moisture, but limited the adobe effect from sun and wind. Over time, as you plant, harvest and shallowly cultivate, this compost gets worked into the soil surface. Over time, the surface of your soil, where you interact, becomes much more friable and loose.

-Dont ever dig deep. Build your soil upwards. Digging deep, with such dense soil, created huge air pockets, which arent helpful. Cultivate as shallowly as possible. Add compost to the surface, and let your soil build upwards.

Hope these suggestions help. When it seems impossible, remember that clay holds fertility, so in time your garden will be tremendous. It just takes time and proper practices. Clay is a totally different animal.

Hi, William. I have very heavy clay soil here in eastern Kansas, but my soil is slightly alkaline, not acid. I have also not tilled at all, only mulched, however whenever the ground has been disturbed due to construction projects etc. I have taken any soil that was already being moved anyway and put it in my compost pile before putting it back to work. I have found that to be been tremendously effective at both improving the soil and increasing the rate of decomposition, because the soil holds water in the pile that would otherwise evaporate away, and it also inoculates the pile with soil life. I am a very lazy composter (preferring to sheet- or spot-mulch on location), so only large pieces of organic matter like sticks, branches, weeds, and vines go in the pile.

I've had good luck with daikon and other Asian vegetables -- I've had daikons 2' long (30 cm) in the first year in previously undisturbed packed clay. Your frustration with these crops may be due to your acid pH or cooler climate, or you may just need to try a different variety that is better suited to your location. I pull my daikons and sell them rather than leaving them in the ground. I've had good luck with New Zealand white clover as a cover crop to plant amongst when I can get it established, but a more reliable nurse plant has been lamb's quarters (Chenopodium album). I just cut it down when it's in the way and let it grow wherever it wants to otherwise; it creates shade and blocks wind (as both sun and wind are abundant here).

For sheet mulching, my favorite green matter by far is giant ragweed (Ambrosia trifida). More on that here: http://blueboathome.com/blogs/ben/sheet_mulching_ragweed . If you don't have giant ragweed in your area, common ragweed should work as well.

Another technique I've found very effective is to raise the beds slightly above the surrounding soil. Even an inch or two seems to be enough to keep the soil from turning to either jello or concrete. Give it a try if you're moving soil anyway.

On the whole I think clay soil is a blessing since it contains (and holds) so much more nutrition than lighter soil. Once the worms have had their chance to mix organic matter in, you'll be ahead of the game. Good luck!

Thanks again. I'm taking notes.
@John
I'll increase the diameter and depth of the wood. In september/october, after a few rains, the soil is so soft I can probably get it 50cm to 1meter deep with a sledgehammer. Don't have a hose with pressured water. Maybe I could do it with the pumped water from the pond, it comes out pretty pressurized.

@Adam
-Albrecht soil test - that's a good idea. I've been reading up on that soil test and it seems like a good idea. I didn't know changing the minerals would do so much for the texture, just thought it was for maximizing nutrient uptake. There's a book I haven't read by Steve Soloman - intelligent gardener - which hits this concept hard.

-Biodynamics/Pfeifer field spray - Haven't thought about that. Will see what I can come up with.

-woody compost - Been thinking for some time about asking around in wood shops or sawmills in the area for that. Possibly much cheaper than my very expensive straw, and may work it's way into the soil faster. Good idea with the poultry manure, as the C:N ratio would be very good with that.

-Digging deep - yeah, I try not to do that, and the "grow biointensive" method which relies on double digging I don't think is for me.

@Ben
Daikons - I got a decent growth of daikons a few times. Once because it was recently tilled and the seed probably got down a little deeper into the softer soil. Other times they have been just random events where one just really goes well. I try to keep seeds of that plant, since it is one I'd like to keep going. The problem could be the acid. I try to sow at the right time, since temperature affects that plant a lot. I might have better luck with Salsify, since Solidago grows wild all over the place and Salsify is in the same family (asters). I thoroughly expected Lambsquarters to go WILD this year, but the spring was really weird and it didn't come up at all (one plant, which is one plant more than last year, I had to import those). As for ragweed, we're desperately trying to grow Wormwood as a medicinal plant, which is of the same family. Perhaps we can really go for that and try to weed-ify that plant for biomass.

Raised beds - We just talked about that today. I've been moving earth on paths, trying to make the place capture more water when it rains. It also is working to raise all the beds, so that should help things. I've noticed that the "beds" which are at ground level with just 2 trenches beside them are really flat and sad-looking. The raised mounds look much happier.

Best,
William

Hi, not sure if moringa grows well in your region, but the root of moringa is like a spike, even in hard, dry clay, similar to the daikon technique.

William James wrote:Thanks everyone for the replies.


@Erich
Good idea about the pigion pea. Seems to be similar to Fava beans which we do grow and they do provide some shade. Confused about Moringa. Is that a tropical tree? Don't know if it will work in my cool Mediterranean climate.

ThanksThanksThanks.
William

not a fan of adding sand (doesn't break down) except for lavender and some herbs. We have red, white & orange clay, and the acidity is nothing but an advantage to most annual crops and berries. Peat moss is a must for loosening the clay/soil. For more traditional beds or swales, I scratched the hell out of the area, loaded a big layer of peat, followed by leaves & clippings, followed by compost and repeated, topping the dirt lasagna with a heavy layer of straw and let it sit from summer until spring. Then tilled and planted. After harvesting the fall crops, I covered again with the dirt lasagna and let it sit through winter and lightly tilled in the spring & planted. After the second season, I bedded it down once again but only with my compost (which I collect all year and empty on the beds in late fall). The beds are now no till, loamy and incredible. Yes, it took 3 seasons to get there, but I'm there.
On our hugels, I dug really deep and built up very high (heavy on twigs, leaves and clippings to break down fast) as root rot can be a problem here with some weeks of cloudy 5" of rain. We mixed some of the clay that we removed with a ton of peat & compost to top the hugel and initially planted garlic, onions and potatoes to help break down the clods of clay. We now have lush summer veggies. It takes time to amend clay when you want to keep the wonderful acid flavor, which I certainly do. good luck and keep us posted please.

@Marianne
I really like your idea of using peat. I was thinking about using it in an "as-we-go" sort of way. Since we transplant a lot, I was thinking of adding 2 trowels full of peat with every transplant. We'll see how that goes.

A question about amending heavy clay: I was thinking of adding a few things to the peat. My intention was to add a small dose of mycelium, a small dose of calcium power, and perhaps some magnesium powder. If I have an 80 liter bag of peat, what amount would you add to that? .
I'm going to be doling it out in doses of 2 trowels when I do the transplants. I'm more worried about the calcium and the magnesium, since I am pretty conservative with the mycelium.

Thanks.
William

Unless you know that your soils are deficient in magnesium, I would not add it to a heavy clay soil. Just adding fuel to the fire. Get that soil tested before adding ammendments, nothing worse than pushing your soils further in a direction you dont want them to go.

My experience with peat is that it would take a whole bog of the stuff to make much difference. It seems at first like it really improves the soil texture, but check back in a month, and the benefit seems lost. Considering the serious destruction of harvesting peat bogs, I dont see it as a good option. Wood based carbon is a much more environmentally friendly, and much more lasting ammendment.

Wood based humus plus BD innoculants for the win, every time. Makes the world a better place too.

Hey Adam - if nothing else, our differing experiences prove that all clays are not the same. I have seen incredible differences long term with the use of peat, but agree with using humus for all of the reasons you mentioned.

William - don't amend to just amend. Clays have an incredible amount of goodies and without a test to discover exactly what your's holds, it would not be worth the $$ or time. With our white & orange clay, simply adding compost annually has made the most delicious & productive dirt.

Keep us posted & good luck!

Supposedly grapes do well on clay.