Raised bed hugelculture

I'm putting in two raised beds for strawberries, for several different reasons.  I would like to do a hugelculture sort of thing, filling the beds at least halfway with somewhat rotted wood, since I have downed trees everywhere.  I would then fill the rest with compost and garden soil.  My concern is that it will shrink too much.  Since it will be planted with strawberries, if the soil level sinks, there isn't really an easy way to keep adding soil like I could with an annual garden.  Anyone have any idea how much it will shrink?  If I can get 4 or 5 years out of it, that would be fine.  If a year or two after I plant it the soil level is halfway down the bed, it won't really work for me.  I can mound the soil initially a few inches, maybe even 6 or so if need be, but I'm afraid a good rain will wash that soil off if I go too high.

Anyone have any thoughts or suggestions?

Edited to add, maybe I can build a sort of wooden wall by putting 1x12's or something up against the inside walls of the beds down maybe an inch from the top and extending up the other 10+ inches?  Then I could add an extra foot of soil and when it sinks, I could just pull the boards off.  Maybe that is a solution?

removing an upper retaining wall section would seem adequate, but if your hugel beds had hydraulic pipes underneath you could pump grow medium in from below as needed and call it permaculture liquefaction fracking.

Jonathan Ezell wrote:removing an upper retaining wall section would seem adequate, but if your hugel beds had hydraulic pipes underneath you could pump grow medium in from below as needed and call it permaculture liquefaction fracking.

Lol, that seems excessive.

I built 2 raised beds for strawberries similar to what you describe. I used packing skid walls infilled to be solid sides about 24" tall. The better you pack the dirt around the woody debris, the less it will shrink, but shrinkage the first year is simply part of the system, and I think it's as much from the dirt/compost settling, as the woody debris decomposing.

So far, I haven't found the strawberries as happy there as in locations with less woody debris. However, it could also be that the new location gets less reliable water, and isn't as warm as the other location, so in some ways, it's not a fair test.

However, settling is definitely worse in the first year. One option is to grow annuals the first year, then top up the bed and plant the strawberries the second year.  I didn't get good strawberries, but the compost had kale seeds in it and I got a great crop of kale!

24 to 30 inch high beds are great for harvesting from. The strawberry bed has tubular hoops over it which I can cover with bird netting, and the height is convenient for lifting the netting to harvest. With the hoops there, I could have put temporary wood up higher to deal with the shrinkage as you're suggesting. For me, just using these beds for annuals the first year seems less bother.

I'm dealing with exactly what you all describing. I built a raised bed. I filled the bottom 1/3 ish with old fire wood super light. Then soil, then, then sticks and small branches, soil 2??? Year old wood chips, soil, compost, topped with with good organic soil.  Last spring? I filled it with strawberries, a couple of peppers, tyme.  
This year the soil level is about 6" lower than where it started.  I did add a little compost, but strawberries can't have there crown covered.  I can tell you I have never had better looking Strawberry plants, and they are loaded with berries.
These are June bearing strawberries, so I will get berries in the Spring, and fall. My plan is to gently remove them after the fall fruiting. Fill the bed to the top, and replant. I figure they will need to be thinned, or divided by then anyway.  
I hope this helps. Good luck

I am in the process also of making a large (4' x 12' x 28") , raised bed. I put hardware cloth on the bottom to minimize moles and voles; the sides are old, metal, corrugated roofing that blew off last year. I have been filling with cardboard, wood and dirt (note dirt, not soil) until I have it about 8" from the top, then I will add soil/compost well mixed with dirt. I heard yesterday from someone in my uke group that sand is necessary in raised beds to prevent the lower portions from getting too hard/compacted. Is this others' experience? I wonder if my starting basically as a hugel mound will/can prevent that, instead, as getting as much sand as I would likely need is $$ or otherwise costly. My 'dirt' here is mostly clay: I have been making soil over the last 10 years in my gardening areas

Thanks all.

@ Barbara Kochan:
I also have a lot of clay and can't easily source sand. Some of my half barrels have compacted over time - like 10 years - but those were built before I started making small quantities of biochar. Using biochar rather than sand to lighten my soil  is the approach I'm taking for several reasons:
1. it adds lots of carbon to my soil and I've read a lot about the importance of that,
2. it provides homes for microbes which helps hold nutrition in the soil during our wet winters,
3. it is certainly much lighter on a per volume basis, than sand is, making digging less work.

That said, I also sometimes lift a section of my soil out, stuff a bunch of weeds/veggie scraps in the bottom of the section, and then put the dirt back on top. We're talking 8 inches deep max. My theory is that it will decompose, and provide some extra goodies for any worms in the area, and worms are good at aerating soil. I can't prove that works, but I haven't seen any harm either.

Barbara I used my soil in the bottom 2/3? Of my beds. My soil has a lot of clay in it. The ground that isn't covered is like concrete.  I have filled most of my beds this way. The oldest is 5 years old ( I think) so far I don't have any compaction issues.  I don't dig around in it, except to plant something. So who knows what is going on deeper. But the part I dig in is nice and loose.  There are a lot of worms. I can't plant anything without finding worms. The one thing I know for sure is I had never had healthier more productive plants.
I didn't use sand, or biochar (though I'm interested in biochar, and might use it in the future).
The only maintenance I do is I sprinkle a little organic fertilizer (what ever I have. This year it was blood meal, Bone meal, green sand, kelp, azomite, biolive, and veggie fertilizer) I mix it together, and lightly ( like 2 handfuls in a bed that's 3' x 8'. Maybe 1/4 cup in my little raised beds) sprinkle in each bed. Then I top with compost, however much is needed to bring the soil level back where I want it. I mix it in a bit . I don't test my soil, so basically I do it to just to make sure there's at least a little of what ever the plants need.
If you have biochar, or can make it, I would use that, but if you don't I don't think it's a deal breaker. Use what you have and just go for it.  

Thank you Jen and Jay

I've started building 24 inch high raised growing beds for our homestead.  My wife loves that she doesn't have to bend over to work them.  Having been introduced to hugelculture here at Permies, I decided I would try it in my raised beds.  I used all the old, punky firewood I had laying around as well as whatever dead sticks and limbs I could get my hands on and filled the bottom two thirds of the beds to take up as much space as possible.  I then filled the remaining third with the excellent compost I had been accumulating from our chicken and rabbit bedding, that having been combined with the fall leaves for several years.  

Our first growing season was last summer and I have never seen plants so happy.  We had peppers, tomatoes, cucumbers and beans, and all of them didn't seem to want to stop fruiting, even well into the fall.  

Our beds have settled a few inches, which I expected.  I was considering making and adding some bio-char to the new layer of compost.  I have researched it some and I do understand how to make it, but I have one question.......Isn't bio-char the same thing as char-coal?

If not, what is the difference?

One more thing.  Might it be a good idea to add a bit of my firewood ash that I saved from the fireplace?

Thomas Tipton wrote:Isn't bio-char the same thing as char-coal?

If not, what is the difference?

One more thing.  Might it be a good idea to add a bit of my firewood ash that I saved from the fireplace?

Quoting myself from this thread:

One other point I would add to the intentionality of making biochar is the production method, and specifically the pyrolysis temperature. Biochar is produced at temperatures between 400 and 750 degrees C. If the temperature is too low, the volatile hydrocarbons are not fully driven off. This is great for charcoal intended as fuel for heating and cooking, as it will be easier to light and produce more heat. But it sucks for biochar, because the pore structure will be poor to nonexistent (clogged up with tars), and much of the carbon content will remain in a form that degrades over time. Also, the graphene complexes that provide molecular attachment points for nutrient ions don't start forming until you get above 400 degrees.

If the treatment temperature gets higher than 750-800 degrees, the graphene structures start to fuse together and collapse into sheets, losing the attachment points around the edges. The micropores disappear as well, so this material won't provide the soil benefits of biochar...the aeration, water retention, and microbial habitat functionality is diminished or lost entirely.

This is a big part of why I have chosen to use the IBI terminology. I don't want to give the impression that you can take low-grade charcoal full of tars and gunk (or something at the other end of the scale that's practically graphite), soak it in compost tea or whatever, and suddenly have something that will do your soil a whole lot of good for the long haul...because it won't work. This is not to say that "accidental" biochar is worthless...most of it is good, because the temperatures reached in a wood fire are conveniently in the sweet spot for decent pyrolysis.

Adding fireplace ash is good for most soils (and great for compost piles) unless you have problems with alkalinity or are trying to grow things that need acidic conditions.

Thank you Phil.

I asked for an answer and I got a good one!

Do you believe making biochar from hardwood in a barrel within a barrel retort type setup can achieve satisfactory result?  That's what I would like to put together as I already have a good 55 gallon drum with lid.  I can easily source a 30 gallon drum and stovepipe for the chimney.

I think Jay's suggestion of growing annuals the first year while the underwood collapses is good, but I also wonder how much compost you could layer in on top of the strawberry bed each year without harming production. They expand pretty vigorously and I'm wondering if e.g. an inch of compost just put on top and let them figure out how to grow through and carry on would be OK.

Christopher Weeks wrote:I think Jay's suggestion of growing annuals the first year while the underwood collapses is good, but I also wonder how much compost you could layer in on top of the strawberry bed each year without harming production. They expand pretty vigorously and I'm wondering if e.g. an inch of compost just put on top and let them figure out how to grow through and carry on would be OK.

Interesting question.  From what I've seen from my strawberries, they are always making new plants from the runners.  Doing as you say may cause the parent plants to become buried over time, but new plants will emerge from the runners every year, replacing them.  

Christopher Weeks wrote:... I also wonder how much compost you could layer in on top of the strawberry bed each year without harming production. They expand pretty vigorously and I'm wondering if e.g. an inch of compost just put on top and let them figure out how to grow through and carry on would be OK.

I've always read that strawberries like to have their crowns above the soil level. That said, I've also read that they're really only productive for about 3 years and then they taper off. So if you lead the runners into individual small pots as replacement plants, and just let the surface drop gradually for the 3 years, you could consider just pulling up the old plants, topping up the bed, and putting in the babies. I've done a version of that, but struggled with the weeding, and had them get overwhelmed, as I think I need to plant the babies in the fall in my ecosystem, and then not totally ignore them... sigh... there's always so many things on my ToDo list!

Jay I totally agree.  Last year I had the most beautiful large and productive strawberries I have ever had. We didn't get any strawberries.  Between the slugs and birds we didn't have a chance.  
My plan for this year is to build a bed primarily for strawberries.  I will build the soil in a hugel ish way.  Place weed cloth on top of the soil . Cut slits in the cloth to pop the strawberries out. Probably put some straw on top to help with moisture retention. I will build a lid made with chicken wire.  This (I hope will solve 3 problems. Slugs, birds, and the bed they are in now is down about 12 inches. I have also been taught never to cover the crown.
Like you Jay I have tons of things to do. I hope to make this a priority. It's such a bummer to see beautiful strawberries on day and a shell the next.
So I guess my solution is to remove them, fill the bed and replant.  Good luck