hugelkultur and clay

Questions please - beginners at this and just building first hugelkultur.  Have read lots on internet but info / opinions seem inconsistent.  We have heavy clay (Low Weald, Kent, England) - good for brickmaking!  Digging spade depth trench about 35ft long x 3-4ft wide.  Logs mainly lengthways to provide stability and shape to mound, but intermediate 'cross logs' to slow down water as on slope enabling logs to soak up more hopefully.  Will be packing in horse manure (we have lots) to provide nitrates and minimise initial voids. The sods/clay dug out I know are then meant to be placed back on top grass down - but I don't want to get this wrong and find the clay seals things up too much and dries out (goes hard as concrete in summer!).  Its digging out nicely in big lumps as currently very wet - do I break it up and use it? / just 'slice' off the thin topsoil and grass and use that? / or not at all?  If I do use where does it go?  On top of the big logs with the smaller wood over that, or the smaller wood straight on top of the big logs then over the lot?  Final topping planning to use well rotted manure (with some straw from mucking out providing mulch too) in lieu of topsoil.  Thoughts?  Aim to plant this season.  Not perfect position as although it runs north/south there is a large oak tree providing shade to the east side.  The west side will get full sun in the afternoons - any suggestions on what best to grow? many thanks and look forward to your opinions please - particularly on the clay question!!

as far as clay goes that looks like some top shelf quality. I don't know too much about hugelcultures but
ive got lots of red clay on my property  and there are places where the soil is now black and almost like bagged professional potting mix after years of adding sawdust and wood chips.

I might layer that clay in the log layers, and mix it with the manure and some compost for the top layer. That will jump start the transformation of the clay to soil.

Agree there is a risk that it dries out and becomes a clay helmet if just that clay on top.

I suggest thoroughly mixing the clay with the manure before adding it to the hugel. Roughly a 50/50 ratio. That seems to help my heavy clay avoid turning into brick layers. I also add a few leaves & small sticks into the mixture. Consider starting with as many earthworms as possible & doing the Ruth Stout method of burying kitchen scraps to encourage worm populations to thrive. I don't bother removing soil from sod. What I do is flip it over & bury it deep in the lower levels. It seems to work but some really persistent grasses or invasive plants might need to be removed first.

Well composted horse manure seems like it might not be great for mulch. I think too many undesired plants (weeds) will grow directly in that. I think a thin layer of manure covered by a thicker layer of straw (or leaves) as mulch might work better.

It looks like you're off to a great start with this hugel!!! Try looking in the regional forums &/or your local gardening suppliers for specific suggestions on what to grow there. Good luck & welcome to permies.

Hard to tell from the pix but it looks like there's a slight slope. I built a trench to capture water on the uphill side of mine. Slowly but sure that's becoming a hugelmoat. https://permies.com/t/117821/permaculture-projects/chicken-hugel

In case you haven't found Dr. Redhawks's excellent soil series yet.  https://permies.com/wiki/redhawk-soil

Thank you all for your responses and the welcome..........much appreciated.  Currently furloughed so cracking on - and now aching!  Lower level in and have sort of 'dammed' the cross logs with clay - hoping to assist water retention in logs at number of points on slope.  Fresh manure and broken up clay soil rammed into the gaps next.

Then medium logs followed by the small logs / twigs / leaves. Should I separate layers or straight onto the large logs once voids filled? We have loads of hay that got wet rotting away - a valuable resource perhaps? Best place?

Plan to slice the top soil / sods off the clay (lots of earthworms within) and place upside down on top - cut down and leaving gaps to avoid the possible helmet!  Will then cover whole thing in well rotted manure and straw mix (nothing currently growing in it).  May need to buy some top soil to go over that?  Either way will add fresh straw to top it all.

Loads of rain already, more due and will empty IBC tanks (collect rainwater from stable roof) onto hugel once progressed further to give it a good soaking.

Few images of progress attached - any further comments / suggestions / thoughts appreciated please - good or bad!

many thanks,  kr.. m

I'm not an expert. I have only built one hugelkultur, and 3 hugel beets.  I think you are doing an amazing job.  Great pictures too.  The only thing I would add is you want to put something between your wood layers.  I have clay soil, and I used that in the bottom part of my hugelkultur. You can use compost, hay, manure, what you have.  I mixed it up.  Once I got close to the top I stopped using my native soil.  I just wanted lots of compost and good soil for my plants to grow in, to give them the best chance until the hugelkultur magic begins.  Good luck, happy gardening.

Thank you Jen, much appreciated. Weather and work has slowed progress - nearly ready for the next layer of logs, broken up clay soil and well rotted manure added - some rotten hay and more muck first! Going to be a busy weekend!

That is some crazy heavy looking clay, Mark.  I can't even begin to imagine how heavy it was to dig out.  It reminds me of the mud-blocks that my African friends built their houses out of when I lived in Africa 30 years ago.  But for them, they would have to mold them in a 4-sided mold and carefully extract them.  In your case, it looks like you could just cut them to size with your spade and immediately start to build a house with them.

I also have clay, so my solution has been twofold.  First, I mulch like crazy several times a year with a huge load of wood chips from a local tree trimmer.  I get upwards of 20 cubic yards of wood chips per load, and I'll put those chips down everywhere -- up to a foot deep in places where I'm not currently gardening.  The orchard gets a new layer of chips at least twice a year.  All that carbon quickly breaks down, and he worm life in the soil is amazing.  As worms and other biota thrive in the interface where the chips meet the clay below, they integrate the carbon down into the soil profile.  I don't dig anything in, but let the microbes, fungi and biota do he work for me.

Second, I've gone to raised hugel beds --- a hybrid raised bed with a sub-soil layer of logs and such like you are creating.  For the uninitiated, they just see normal raised beds.  But what they don't see is a foot below the soil surface, all those logs and sticks breaking down.  

I'm not a fan of the sloping sides of a hugelkultur for planting many crops, so I used timber frames to keep the soil flat/level.  I get the best of all worlds: the carbon and fungi from the buried wood, and the ease and improved soil from the raised bed.  If your hugel doesn't work out as you wish, you can always simply go back and build sides around it and turn it into a raised bed easily enough.  My compost seems to go a lot further this way, because it doesn't fall down the side of the mound, but rather, stays in place.

Please continue to post pictures.  This is a fantastic project.  Best of luck.

I love your work Mark!

Progress - nul points!

But think of all that moisture those logs will soak up.

Progress! Next layer of logs. Gaps stuffed with well rotted hay. More logs.

Dog’s knackered too!

Looks awesome Mark! Can't wait to see how that beast performs

slowly getting there. Next layer well rotted manure. Still getting frosts here but hopefully seed in a week or so.  The dug out clay have made three sided 'wall' to hopefully trap water on slope and moved the old rotten hay we lost. Maybe a haygel once rotted down.  Might add some manure and see if potatoes grow?  Hoses are from IBC tanks collecting rainwater off stable roof.  

no idea where the photos went!  will try again...........

meant to ask please any suggestions what might grow in the hay? if anything? are potatoes as I think a good idea??

further and far more important question please! How thick does my well rotted manure need to be??  Have started but don't want to go over again in a second layer as think more likely to slip off!?  (Appreciate it will be limited what will grow in this until more mature - squashes etc). Back on it tomorrow.......... many thanks

Wow Mark great job.  I don't know how thick the manure layer should be, hope someone with more knowledge answers that question for you.  I do know the taller you go the more likely it will slide down the sides.  It's just part of the process. There are posts about solutions for that. I used sticks to make little dams, and mud in the tough spots.  Your doing an amazing job. Your going to be able to grow wonder things so much easier then conventional gardening. (Once the hard work of building it is over).  Happy gardening.

Finally there - more work than I ever anticipated!  Big dent in the muck heap - good stuff at the bottom mixed in with what topsoil was there.  Plastered it on reasonably thick - maybe 4" on the top and anything from 2-4" on the side stomped in by my size 12s - one forkful at a time. Slabs laid loose most of the way round (freebies!) to provide more heat and reduce mud. Now to seed it during the next week, cover with straw and hopefully some magic will happen.......Have a good mix of different veg seeds and will see what works - fingers crossed....

Such a sweet project! To answer your question, many people plant potatoes as the first crop in a hugel. Jerusalem artichokes should also be a good choice.

Get's blacker as you add manure and other organic matter.

Okie here.

Oklahoma translates to "Red Dirt" because of high iron clay soil.

I'm in the Northeastern "Green Country" part which has a mixture of msny soil types but my land had clay soil.

What I did was lay down 6" of tree leaves first and top it with 3" horse manure. Mostly to kill the bermuda grass and not have to till it.

Like you did I put a lot of muscle into it. Many truckloads of materials got added to the top of the flat lawn.

My theory is that clay is just compacted rich soil, and all it needs is moisture and it expands, and my eeriments have borne that out.

I put logs down to build berms and used the in between dirt to top them.

Then I put mulch in the sales and the clay expands and makes more soil(More than the mulches added) And I get more I can dig up.

I've seen soil grow in many places. In Kansas City with Limestone karst the soil expands also. So much so that brick retaining walls bend over and get ruined.

So you're doing it right.

You're probably not going to need many MINERAL supplements once the biome transports thinhs where it needs to be.

But I would change the way I did my log berms next time I build a new one.

I'd leave a gap in the middle.

For asparagus.

Like THis:

The reason I wil build my next log berms with the big earthen filled gap in the center is drought and capillary action.

I hypothesize that asparagus and other tap root/deep root plants will PUMP water to the top of the berm. And Distribute it/share it with other layers of the berm.

My experience with Oklahoma Climate is the best place to plant water-needy plants is down on the lower third of the berm on the downslope side.


By using deep rooted plants at the apex of the berm you might get better water distribution generally.

But you need a GAP for them to build that rootsystem.

They can't root THROUGH LOGS.

Also I'd innoculate the tops of the top logs with mushroom spawn.

Next time I build one.

I haven't PROVEN these ideas yet, just want to test them.

If you like to walk on the top of a big berm, like I do now, you might not to want to build it that way.

But mine aren't so tall I need to walk on top.

I'd rather everything have WATER.

I'd inoculate all the large logs with mushroom spawn.

But focus on the top later if resources are tight.

I'm guessing mushroom fruits can go up a long ways.....I just started the shitake log stuff recently in open air.

I think for most permaculture you should like the logs to get digested fast.

It's nice having them in there as sponge, but digging up dirt to top them is the hardest work.

My whole setup is a gigantic sponge.

But I constantly add mulch to it.

I'm looking forward to the day I can dig RICH SOIL off the berms to start new ones, instead of digging the flat areas.

Really cool ideas, Simon. In places, people have found that plant roots will travel down between the bark and the wood itself, with a vertical log. Vertical logs also wick water upwards by themselves, so the tap-rooted plants can enhance that.

I agree with you that clay is basically awesome soil waiting to happen, but if you just add water, you’ll probably just get wet clay, IMO. I think that clay is basically a rich mix of all the rock minerals you could want, ground up super fine, and the missing ingredient is carbon. Lay it down, things will come in to decompose it, humus is formed and trickles down, and BAM, you have awesome, structured soil.

Update: finally seeded and mulched after late frosts. Random mix and fingers crossed!  3000litres + of H2O from stable roof this weekend 😀 (3 ibc tanks collecting from gutters). Hugel on a slope so hopefully the whole thing will be well and truly soaked. Would be nice to see inside - hopefully the ‘mini dams’ are working?!?!

Hi all,

As half expected anyway (despite my optimism!) very little has grown in the manure - it was always a gamble.  Few shoots here and there from the mixture of seeds but these have been eaten and/or stopped growing!  Oh, and some small clumps of grass / few minor weeds which will pull out easily.  Clearly the manure too strong and not suitable as a growing medium to get things started and need to add the topsoil as it's meant to be - but didn't have any, or the time!  To buy and get it delivered isn't cheap - but may have to?  In the meantime things will I am sure be slowly rotting down and maturing ready for next season.....certainly must be nice and wet inside as have continued emptying rainwater direct into hugel.

Question please:  If I dig out 'topsoil' from elsewhere how do I get rid if grass/nettles/thistles etc?  Will it kill it off by cutting sods and simply laying on hugel upsidedown?  Aiming to do this from an old ditch that needs clearing anyway.......probably over 30 years since last cleared when the land was hop gardens way before we bought the land for horses (been here 2 1/2 years now).  Hopefully will be a decent layer before hitting the clay.

Simply flipping sod over slows the grasses down but eventually they will return unless you add a thick layer of mulch on top. I suggest crumbling the sod with a shovel or your hands then sifting the roots out with a screen. Or banging big clumps of sod together to knock most of the soil loose then use the roots & grasses for composting. Those methods are more work but it is much more effective.

I think horse manure is generally good to go right out of the horse. There might be another problem. Weather perhaps? Bad seeds or the wrong crop for your area?

Mark, later in the day I remembered this possibility. Hay grown with it, even after being eaten by a horse, is bad for gardens. Very bad.

thanks Mike, seems Aminopyralid is unlikely - we don't use neither does our our current hay supplier, albeit before that we don't know?  Anyway, sod all grew as half anticipated - the few shoots that appeared disappeared, probably eaten.  However, as the year progressed grass and broad leafed weeds started to appear. We've also given the adjacent oak a massive haircut (for various reasons) and now have good sunlight from mid-late morning.  Have been adding 'clay topsoil' -  albeit nowhere near enough but as things have settled, and clearly rotting have given it another go. Mix of different seeds including swiss chard, courgettes, radish, peppers, carrot, leek, lettuce and some very well rotted manure over + straw and a good soaking.  nothing scientific or neat and tidy as time very limited.  Its still wet inside despite little rain in last month or so.  see what happens next..........  The 'haygel' has shrunk and was also covered in wood chippings - a few potatoes planted a year ago are growing  so have added more.

be back with an update......... hopefully a good one........?

Photos....

Looks great Mark. I'm glad your hugel is alive & well!

Hi Mark!

It's definitely a labor of love isn't it? Hope you have good luck with it this summer.

Chucked seeds in spring not expecting much until we get some top soil on and pack down the loose/holes that have appeared. But clearly alive and maturing! Swiss chard and a courgette. The ‘haygel’ has produced a drop of potatoes already. Second lot now in. And a squash growing. Hopefully have some soil on it next year.

Thanks for the update Mark. It's fascinating to see the heap mature. I suppose it's too soon to see the real benefit of water retention from  the buried logs yet since they won't be breaking down much yet.

Hi all. Update and question please.  Was neglected last year and overgrown. Covered in old tarps etc over winter and only just had time to uncover and clear last of weeds etc. Random scattering of different veg seed raked and watered in. and some potatoes. Now fingers crossed.  The manure and hay is looking very much like good soil now so hopefully be good for growing.  All fingers crossed.  The (possibly daft) question is please do I need to keep seeds watered until they start growing, or will the water from below provide sufficient humidity as it will once growing?  It's very wet down there! And if I need to water at what stage of growth do I stop?  

And some straw,,........😀

You need a lot of rotting wood the more the better .and crushed rock leaf and green grass that’s not seeding .i live here in Hawaii have terrible red clay soil .i find grow on hillside with check log terraces filled with wood leaves etc works better in clay

Thanks for the update!

Those beds are looking great and you have some serious great logs.

Any organic matter you can add will help with the clay.

Round courgettes and chard love it. Just keep giving! Different courgettes or cucumbers and maybe pumpkin on way. We'll know once the fruits appear.  Seeds were very random!  Will take more care next season. Few carrots onion garlic slowly growing. Other stuff the rabbits have had. Maybe a nice stew come winter!