are you sure that was compost you put down. where'd it come from?

the solution is more compost...compost,compost,compost and leaves, leaves,leaves. get as many leaves down as you can before winter, then add more leaves, leaves,leaves and compost,compost,compost when the ground warms.

oh & stop tillin

Where are you doing this? Is it possible thats its an old construction site dump? Common practice for years around Colo; dig a hole and bury the construction scrap. I'd sure go for raised beds.

Those lumps of clay are workable early in the spring, after a winter of freeze - thaw cycles. A certain moisture level, and the soil can be worked pretty well. You can tell by how easy a clump crumbles, when its just right. Drier soil still works, wetter; you'll make bricks.

Welcome to Colorado Clay. We do manage to grow stuff. Better gardening through massive amounts of compost, and it does get better as the years go by.

I had good results breaking up a load of clay "topsoil" by mixing in huge quantities of coffee grounds (by hand, with a garden fork). You might also stick to the simpler crops for the next few plantings as the soil reconditions - legumes, for instance. And I agree with the no-till advice. One of the things tilling does is mangle the soil life - earthworms, for instance.
-O

I agree with previous posters that the addition of compost is the way to go. Uncomposted organic material dug in may cause nutrition problems next year.

Also don't use a rototiller. It destroys soil structure - reduces the soil to a powder. The crumb that resulted from earthworms and plant roots and provides drainage gets destroyed. Use a garden fork - the one with four flat tines.

In the fall, rough dig the plot so that winter freezing will help break up the soil. Dig in the compost in the spring.

I agree that you probably tilled in uncomposted material - most likely would be wood dust or bits and pieces of wood. The decomposition of wood requires a lot of nitrogen. If the fungi cannot get nitrogen from the air, they rob it from other sources. Once the decomposition gets past the high nitrogen requirement, then your soil will reestablish the nitrogen and things will grow again.

I think the only thing you did wrong was to till the "compost" under the surface. Had you left it all on top, the way Mother Nature does in the fall, then you would have had much different results.

What you did was add not quite enough organic matter to that clay soil and it is reacting as most all clay soils react when not quite enough organic matter is added. Add lots more organic matter.