Growing things in containers is a bit different then growing things in the ground, or even in raised beds. In containers water retention can be a problem so often something, usually vermiculite or perlite, would be added to the peat moss. finely ground bark or wood chips, or what ever else that potting mix is made of to aid in moving excess moisture through.
I have worked with raised beds, 6 inches high to 4 feet high, that have had good garden soil put in them with no problemn with water retention. What I have seen is drainage is too good unless adequate levels of organic matter are added, just like in a ground level bed.

ken, a typical commercial potting mix will rather quickly decompose in a healthy, microbe filled soil environment. That's probably the primary reason that it isn't recommended as the primary ingredient in a raised bed. Once the peat based potting soil becomes more and more decomposed, it loses any porosity it may have had in the beginning. Make sense?

Container plantings don't have the kind of microorganism population. And we don't want them to.

Granite grit is an excellent amendment for outdoor beds and container plantings, as is perlite, and bark fines. Vermiculite collapses very rapidly and is of very little long term (meaning months) in outdoor soil or in containers.

If you are interested in trying some granite grit, check out a local farm supply outlet. I buy poultry granite grit often used for chickens and turkeys from a 'feed and seed.

The mix I'm using so far in my new raised beds is, 20% compost, I've made, 20% store bought compost,20% soil,20% worm castings, the balance varies for experimental
purposes, of chipped alfalfa, more soil, coco-peat, and a couple of beds are 60% compost. I have 16 beds in all.
Do you think I'm overloaded with compost? As far as depletion goes with the compost, I can always add new each year. I also added processed chicken manure to one of the beds, but only one, as I'm worried I have thes beds too rich in nitrogen already
I sure like the way Jon's beds look, and am impressed with the way he can push his arm to his elbow in his mix. Weeds have to come out super easy in his mix.
Thanks again
Ken

Organic matter, compost shredded leaves, wood chips, etc. will all eventually be "depeleted", digested because that is what happens in a good, healthy soil. The Soil Food Web digests the organic matter and uses the nutrients that are in that organic matter to feed the plants growing in that soil.
Getting too much organic matter into the soil creates other problems, such as moisture retention, so plants growing in soils with very high levels of OM which holds too much moisture will slowly die from root rot.

Ken, I think that even if you don't have problems with moisture, you'll have problems with your soil sinking really seriously by next year. I filled a raised bed with too high of a percentage of organic matter, and while the plants did great, it eventually started sinking, and now I'm faced with the proposition of needing to dig out perennials and re-fill the beds with a higher percentage of plain old soil. If you're growing annuals, you may be in a better position.

Hi Ken,
My original soil was clay (not like pottery clay,but clay nonetheless), I dug down at least 3' with my excavator (some places four feet) and proceeded to mix in lots and lots of Decomposed Granite,Pumice and literally tons of compost, I mixed that stuff up until the end product did indeed resemble commercial potting mix (at least by sight/ I have no idea what is in their mix). All I do now is continually add finished compost to top off my beds, and you are correct, if I happen to see a weed (rare=because of French Intensive/BioDynamic ....ie.. crowding) planting style, it pulls up very easily ..... So, it sounds like you are doing great,and it you want that same look add more Decomposed Granite and Pumice....Totally Rocks ! !

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Everyone likes the way Jon's beds look.
ken1 regardless of what you do please up date this thread or start a new one on what you found in your mixes on your 16 beds.
Give us the title of your book also.