Tiffany, I agree that organic matter IS absolutely vital for creating or maintaining soil from almost any starting point.
Maybe with HUGE amounts of OM added to 80% clay, sand, grit and fibers are not as necessary as they seem to me. I've never had more than a few inches to add per season or per year, except for when I first made soil. Then, if I could afford 30-40% compost, it was a rare event. As I've mentioned, 12 months later, the (clay + compost + air mix) had reverted to clay + subsided bed.
The OM is vital for soil life as well as for soil structure, but you can GET BY adding only 5-20% OM per year if all you need to do is feed the soil life.
Even if someone makes some INorganic mix with good drainage and aeration, the lack of OM starves any "soil" organisms. That's hydroponics or soil-less gardening.
By the way, people with sandy soil who add only 10-15% clay can get good results, not concrete, but I suspect they already had or added "enough" OM to make it work. The voids and channels around coarse sand grains provide drainage and aeration, and even a little OM supports soil life and SOME soil structure.
P.S. My theory is that soil drains and admits air if the "coarse phase" supports itself with big open spaces between the clods, peds, pebbles, grit or coarse sand. Then the "fine phase" must be small enough that clay and silt never fill the open spaces, even after heavy rains and several years encourage the fine phase to migrate downwards and clog all the open space 12" below the surface. Also, if the "coarse phase" is some kind of an aggregate like clods or peds, they must not be so fluid that they "ooze" or flow into the open spaces and fill them.
I'm just offering that as a theory, not saying that what I've seen in my yard "prove" it. Something has to maintain open channels, and the rest of the soil can't completely plug those channels.
>> When I lived in OH, I started many new beds in pure clay, in housing developments where they remove the top soil for sale, dig the basement hole, using that really deep solid clay to make a gentle slope from the house down to the street. Suck your shoes off when wet, cracked like the desert when dry.
That does sound like awful, terrible, unusable clay soil. Somewhere between 50% clay and 100% clay. Once it is compacted, it might be difficult to tell the difference between 50% and 100% clay. Both are hard when dry and impermeable. Squishing it when wet might tell something, or using sedimentation to distinguish silt from clay might make it measurable.
>> By doing nothing more than covering the soil with tons of OM,
In my yard, I did not find that my clay + (moderate amounts of compost)
remained usable for more than 8-12 months. It rapidly reverted to pure anaerobic clay. To compare our results, I would have had to have bought 5-10 times as much compost as I did.
Also, maybe my first few years of compost was too "digestable". Compost containing (for example) coarse wood fibers or bark fibers acts like compost + sand or grit until the fibers decompose.
I need to go back, find that link and read what was in the link. But if a microbiologist wrote it, not a soil scientist, it probably dwells on the biological need for organic matter to soil life. I totally agree with that - 100%, not 90-95%.
