Biochar with clay?

I live near Oklahoma City. My "soil" ismostly just hard red clay. If I'm lucky, I might have an inch of black top soil. Should I spread out the biochar on top of the clay, mix it into the clay (6 inches?), Or do I need to bring in top soil?  I've heard ratios of 10% char, or as high as 50% char?

How's your earthworm population? If you've got good worm numbers, spreading biochar that's well crushed (mostly under 5mm particle size) and lightly harrowing it into the topsoil will do the trick. Earthworms will ingest the biochar bits and grind them in their little gizzards, and spread the stuff deeper into the soil as they burrow.

If you're impatient, you could till it in, but this will kill a lot of your worms and other soil life in the process. As far as amount goes, you will have a hard time getting 10% biochar by volume into your topsoil (A horizon)  over any appreciable area. 1-2% is a good starting point.

With the clay of OK you would be better off starting with mulch to cover at least 3 inches thick, 6" to a foot would be even better.
Once you have that mulch breaking down into smaller sizes then you would benefit most from adding char as you acquire it.
The decaying organic mulch materials will leak good stuff to the soil surface where it will begin to change the clay into friable soil.
The longer you simply keep the ground covered with a good, thick layer of mulch, the better the soil will become.

The terra preta discovery that started the whole biochar phenom took around 500 years to get to the point it was at when discovered.
All that means is build some soil first (char in clay isn't going to do much conditioning of the clay).
To build soil compost and mulch along with living plant roots are the key players, once you have a fair amount of soil with good (3-10%) Organic matter you will have enough soil biology working to take advantage of the char.

As Phil brought up, using a tiller is not a great idea for installing(amending) char or any other amendment material for that matter, especially if you have a good supply of worms working in the ground.
If you don't have any measure of soil life now, then you might want to till in some compost for a start towards fertility but you only do that once, from then on you are working on the surface and letting the worms come and do the "digging in" for you.

To help get a great diverse group of microlife I recommend IMO 4 under the compost layer.  Biochar can be added to each layer.

Incase you do not know what IMO is, it is from Natural or Korean Farming:  Natural Farming and Inputs

We're building a house in the woods. I honestly haven't noticed any earthworms, but I haven't gone looking for them yet. I have tons of wood debry, and rather than burning it all away, I wanted to work on making it charcoal to turn into biochar. Once the house is finished and all the infrastructure is in place, then we'll be looking at doing some gardens. Once my garden beds had enough biochar, I was going to start spreading it in the woods. For the woods, was hoping that I didn't need to work it into the clay, or bring in extra organics.

Thank you all for your advice!
Thank you Harry. I'll look into that.

Stephen, do you have access to any animal manures? By co-composting your biochar you'll get it fully charged up and the partially broken-down manure will be a massive enticement to the worms. It doesn't take much, just enough to make a slurry and mix in with the char.

I have 25 chickens / ducks / guineas. But they're free range, so not much manure to clean up. I have a regular compost pile going. Also have have read about soaking it in compost tea / worm leachate / urine. Never tried any of them, So I am open to recommendations.

A moldboard plow might work to turn the soil without killing too many worms.

Ellendra Nauriel wrote:A moldboard plow might work to turn the soil without killing too many worms.

My concern would be forming a water-impermeable layer at the bottom of each furrow in clay soil.

Stephen, what I am taking from this is that you don't need biochar right now, except perhaps in garden beds where you can amend to a higher ratio than broad acreage. If you have access to a chipper, I'd use it on all the wood you had planned on charring and spread those chips over the areas you want to amend first, but only so far as you can with the minimum depth Dr. Redhawk mentioned, with the deeper mulch being more desirable.

I would perhaps make enough biochar to compost with, as suggested above, and apply that as top-dressing or with plantings.

-CK

Chris you are correct.

Thank you all for the advice!