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.