You can enrich it by making mulch of your own. You can use things like egg shells, potato peels,skins from fruit and fallen leaves. Using a bin place these materials in there along with a little moisture and an earthworm or two. It takes some time but when it is ready all will have disintegrated. Add it to your soil.
Enriching clay soil is probably going to require a bit of patience and hard work. I'd first start off by renting a garden tiller and adding coarse sand and organic fertilizer. You'll probably want to work the soil this way once in the spring and again in the fall. Year by year you should see better results from your plants.
you can enrich poor clay soil by adding peat and compost. Compost from your scraps are generally preferred as they are much richer in mineral content. Also you can add earthworms so that air could be introduced.
In one word - compost! Begin a compost pile today. Many municipalities give free composting containers. Put in all your vegetable scraps, yard waste, leaves, etc. In a few months you will have compost which you will then dig into your clay soil to make it more friable or light.
I had heavy clay soil in my yard and what I did to enrich the soil before planting was add michigan peat to my soil and mix it in well with a spade. Sand may be added to loosen the soil also.
Add organic material, like peat moss, grass clippings or dead leaves, cultivate them in. This will produce richer soil. If you use chemical fertelizer, you just have clay with chemicals.
The way to enrich pretty much any soil is to add lots of compost or to make compost on the site -- trenching. I use French Intensive where you dig a trench, fill it with organic material to compost, and replace the site soil on top.
