Here in Madison, Wisconsin, we have clay soil also, although it might not be as severe as your soil. We have a compost pile, about 8 foot diameter, and 5 foot high. It makes about 25 gallons of finished compost every year, and I put this material down on the garden plot, in the spring, and spade it in. This has been going on for 10 years or so. The garden soil is now much improved, looser, and more easily worked. The vegetables and raspberry canes do well, so it is worth the effort. At least, it feels that way around harvest time.

Yes, clay soil is the pits. It might help to turn the hose on to just drip for a while right over the area you plan to dig up next.

Then when you've dug as deep as you can, fill the hole with water and dig a little more once it's drained. And repeat. That's how I managed to dig a hole big enough for planting a tree.

If you encourage earthworms they will do some of the work for you. Several years ago when DH dug a new perennial bed for me we were amazed to see worm holes deep in the clay base about 2' down. I wonder if they either winter there or stay cool in the heat of summer. I don't know all that much about earthworms but I know they are very helpful in the garden.

I know some plants such as dandelions have deep roots which can help loosen the soil. Not that I'd deliberately plant them and I try not to let many go to seed, but when I remove them I see how long the roots are into the clay. Sunflowers also have deep roots and they would be a good crop to plant.

Just keep on adding organic material and eventually you will have soil.

Make a compost pile instead of trying to dig into that clay. The only way to make that clay soil better is to get organic matter into it, lots of organic matter. In Indiana, Ohio, Oklahoma, Texas, and California amending the clay soils I found there took some time but there was always great improvement after lots of organic matter was added after some time. In Ohio we could simply pile the fall leaves on and by the next spring the soil was loose and workable, but in another garden in central Michigan the clay/organic matter interface never got together, never did anything and that clay soil required tilling in of large quantities of organic matter.
The only way to attract earthworms is to provide them with a food source, organic matter.

First, are you sure you have true clay? Silt will give the same impression.
To find out, you can use the jar test that Kimmsr has plentifully posted.
I'm not against adding organic matter to soil, but bear in mind OM is a consumable. If you want permanent results you need to modify your existing soil triangle. That will take some work that will need assessment- a garden bed, no big deal. Acre or more? Probably not worth it.
There's other views about clay gardening, I suggest you do a search here for posts by pls8xx who has a unique working approch to straight true clay planting.

Compost, peat moss, coco coir, humic and fulvic acids are what you want to modify the clay soil.

There's nothing fundamentally wrong with clay, it just needs organic material to loosen the soil structure.

The compost you make is a vey good addition to any soil. Peat Moss, Coir, and purchased compost can get very expensive and should only be used if there is no other, more readily avaiable organic matter. Since humic and fulvic acids will develop in any soil well endowed with organic matter there is no good reason to spend money on them either.
In addition to compost tree leaves make an excellent soil amendment and in many places, even some areas of Idaho, they are in abundance.

Barb roselover, you don't give your location. I'm in Colorado, 30 miles north of Denver and this sounds familiar. I have clay loam, 7.9 ph and almost need a jackhammer in the spring to break it up. Someone on a post said adding sand to clay is making adobe bricks, not a good mix. You need to add lots and lots of manure and compost to combat this and it just wore me out. So now I choose where I want decent soil and do raised beds, then take down the raised bed and move it every year. Over 4 years I now have a 20 X 20ft area with great soil. That's a big enough veggie garden area for me and other than the flower beds, I leave the native soil native. It's still a lot of work, but not as bad as digging in that much compost everywhere. It takes time and patience, but you'll get there.

According to an article about making Adobe bricks from New Mexico State sand is not needed and mixing sand into most clays will not produce Adobe bricks, but for sand to be worthwhile you will need to add a substantial amount and it is much less expensive, and generally easier, to add organic matter to your soil.
Sometimes yo may need to till the organic matter into you clay soil but I have found that most of the time simply laying that OM on the soil as a mulch the same thing will happen, eventually. Absolutely if you lay compost on your clay soil it will not be worked into the soil by nightfall as it would be with tilling, but you would do much less damage to your soil, and with patience, that organic matter will get there and your soil will be better than if you tilled it in.

Here is how you solve this problem.

Place three inches of a good rich compost over the area you want to loosen up. Water it well. I mean saturate it three or four days a week. In four months you will have soil you can dig with a teaspoon.

Do not, I REPEAT do not try to loosen clay dirt with sand. Clay + sand = cement. Microbial matter is what loosen's soil. By soaking the compost with water you are letting the microbes in the compost enter the soil so they can to do their thing - loosen the soil.

Or, put your compost pile over where you eventually will wnat to have a garden. You will accomplish the same thing I already said to do. The earth under a compost pile will be the softest, most wonderful soil you could ever imagine having. Some people move the locaton of their compost pile avery couple of years for just this reason.

Or, you could rent a heavy tiller and till in 4 incnes of pure compost - twice. Compost buffers the soil's ph and it puts organic material into the soil so it will stay soft. If you till soil without putting in enough organic material you will have rockhard soil again in a matter of weeks because you have not changed the compostion of the soil. Having clay soily is like walking a great big deck of playing cards. Clay particlse are big and thin. Organic material works it's way in between the particles - which allows air and water to move around in the soil. If you don't change the soil you will have what you always have.

Water will not soften clay soil - organic matter will.

Don't try to burry your scraps in the ground thinkingthe coons or rats, or other critters will not find it and dig it up. Unless you burry it a couple of feet deep they are going to find it and dig it up.

Other than a stand-alone compoist pile, you hsve four choices. Make a raised bed. Make a lazagna bed. Do what I described above. Use a tiller to get as much (and I mean as much) organic material as deep into the soil as possible. For clay soil as hard as you descibe I would till 4" into the ground and then do another 4".

Finally, remember, organic matter breaks down over time. If you don't continually add organic matter to the soil it will eventually revert back to the rock-hard dirt that you have now. Keeping soil soft and fluffy is an ongoing process. It is not a set-it-and-forget-it thing. Organic mateial has to be replenished in order to keep the microbial life alive. When you realize it you will understand that it is the living microbesd and their dead bodies that actually gets in between the clay particles and keeps them from sticking together. As the soil loosens, allowing air and water to freeely move, you will get worms to come because the living conditions will be good and there will be lots of microbes for the worms to eat. Yep, microbes are earthworm food - they don't have teeth to chomp lettuce, saw dust, garden waste, etc. They eat bacteria and fungi.

You can only turn your hard clay dirt into soil by incorporating lots and lots of organic matierial into it.

Tom

P.S. If you till the garden bed, only do it this one time to get the process started. Aftre that just put the compost into the areas where you inend to plant crops. There is no need to till because the microbes move with the water as their mode of transportanion.

Tom's right about sand + clay acting like concrete. If you have the right ratio it works, but it takes a LOT of sand. I have put a mix from river floods on my garden, it's both silt and sand, and I've had some hard spots develop even with that. When it's moist it's oh so beautiful, but when it dries out it can be brutal. OM is the way.

Thanks so much for your hints. I would love to have that much compost or organic matter to use. I don't seem able to manufacture that much. We used to be able to get it from the city, but this year their budget will not allow them to do it. It really wasn't that good, I might add. If you do not have the organic matter to add, just what do you use? I purchased three bags of manure and added some other dirt with it but it only covered about two of my six raised beds--not counting my rose and flower beds. My son commented that he couldn't believe I paid money for that. He has cows out in the field, but tried that, and it was full of weed seeds. In the Fall, we have plenty of leaves, but they are not shredded and just seemed to lay on the garden all winter. They were about two feet deep, and we tilled them in this spring. I live in the northern part of Indiana. I loved Colorado, when we were able to travel out there--seveal times. My daughter lived in Aurora.- Barb

barb, you're almost there. Keep putting those leaves in, even if they're not shredded. Ma Nature doesn't own a shredder. They'll break down and become almost nothing in a few months so add a lot. Anything organic, straw, oatmeal, rabbit food, grass clippings, weeds, just till it all in. It all breaks down and feeds the soil. Eventually you won't have to till, just lay the stuff on top as mulch and it incorporates itself when those microbes are active. Weeds? well, that's another story. Best wishes.

What I would try for trench composting in clay is this: dig the trench as best you can. Add your food. Pile on as much non-food compostables (like dry leaves, ripped up newspaper or cardboard) as you can (at least 6"). This alone will certainly not keep away critters. But if you have some kind of fencing - maybe chicken wire fence - you could lay that on top of it, and weigh it down with rocks and bricks. (Now that I think about it, this might be a take on "sheet composting")

I've had a leaf pile sitting in the same place for two years. I had put it on top of the hardest clay you can imagine.

This year I moved the leaves to another location. The ground underneath wasn't perfect, but I was actually able to dig into the soil with my hands and it felt sort of soft underneath my feet.

The point is, the more life you have in the soil, whether it be critters, decomposers, microbes, etc, the better the soil will be

Hi Barb,
I had the same soil. I did the raised beds using old boards from our deck. Each year I would add whatever compost that I made. Now, we have very rich black dirt. You could also try soaking the soil, adding compost and getting some Alabamba Jumper worms. They reportedly do a good job of breaking up tough clay soils.