I can't give you exact ratios, but I can tell you my soil began as nothing but clay. I have found adding sand alone will give you a concete-like mess, I've added lots of peat,
manure, and top soil to my borders over the years and it's finally becoming a nice garden loam. If I were you I would probaly start with mix of 3/4 peat moss and 1/4 sand.
this should here break up the clay quite a bit. I try to add more peat every time I till (spring and fall). Also in the fall till your leaves in, adds great nutrients and helps break down the clay.
hope this helps,
The best thing you can use is use Organic Material; preferbly compost. Till in a minium 4" of compost per 100 sq ft. The more the better.
It will take time but the end results will be worth it.
You should also mulch your plants with compost.
Sorry for the belated reply; I was out digging up my clay...
Actually I hear that gypsum is the preferred amendment to clay; something about sodium being swapped for calcium chemically, I think. If you add sand to clay you get concrete; not good.
I ended up adding both gypsum and compost and since it was basically an open field got a friends' backhoe in to mix it all up. Too soon to tell if things will grow; my main problem before was no drainage and root rot. At least now the soil drains quite well so I'm hopeful.
I got my gypsum at Home Depot; they had both the straight stuff and "pelletized" with fertilizer added in. After trying to spread the powder evenly and failing I went with the slightly more expensive pellets and just ran it through my drop spreader and went back and forth.
Kind of by guess and by golly I put down 500lbs in 5000 sq ft then rented a big hydraulic tiller and tilled it in about 8-12 inches. The whole thing was actually pretty fun for a weekend. The only thing is now I can't blame the clay for my failures...
this si a product made just for clay, a once tretment.
Also Sawdust is great for adding to clay because it take forever to break down and it keep sthe clay from compacting.
YOu dig at least 4" inches down and put the sawdust, don't do it when the clay is wet in clumps.
then you add you compost on top or throughout the clay on top of the sawdust, it works the top layers.
I would use compost heavily. Composted manure would be great to add, a bit of leaves, pinestraw, very little peat moss...if you have vermiculite, or perlite...Id toss a bit of it in too. Gypsum pellets are supposed to break up the clay...Id use a good dose of that along with the compost...and mix completely. Pinestraw makes a good mulch...it will break down. If your soil gets a bit too acidic...throw in a little lime. I think adding Epsom salts to the mixture is a judgement call. I have it in my veggie garden. I also added bat guano, and earthworm castings...organic is GOOD for your soil.
Don't know if anyone is watching this thread anymore, but I'd like to offer a tip for improving clay soil (it's a secret used in English gardens and I can attest to its benefits).
Besides digging in all the previously recommended ammendments, incorporate small-sized "smooth surfaced" pea gravel. Pea gravel of this specification slips amongst itself (contrary to how sharp edged granit chips grab each other) therefore, the soil in which pea gravel is incorporated becomes very loose. I had clay, now I have wonderful soil through which water can permeate!