Handling Hard Clay Soil:
Clay-Loam soils one of the best soil types to grow in; however, Clay soil (without the Loam) can present some problems. The good news is that these problems can be altered to provide you with a good soil for working and growing.
Clay's benefits are that it has more surface area (being Platelets) than silt or sand soils. This provides the ability to hold more water (many times it's weight) and nutrients than other soils. The biggest problem is that Clay( again because of it's platelet structure ) will turn to adobe if allowed to dry. This has a tendency to make it hard to work in dry times.....if you know what I mean? You must keep it moist.
So, let's look at the ways we can do that. First, if we add calcium in the form of Gypsum or garden Lime, we can begin to loosen Clay's platelets natural tendency to stick to each other. This will loosen the soil so to speak and help make it more crumbly. Don't be shy with this element. Use some very fine grit to get started and use coarse grit for the long haul. You can add some every 5 years or so. Check your soil tests yearly.
Next, you want to get as much organic matter---COMPOST--- into your soil as possible. In Indiana, you would need 2 inches to start and 2 inches annually as it will be consumed in the soil. This organic matter with help keep the soil loose and provide water holding capability along with nutrients. I cannot emphasize the need of Compost in your soils---it is the Alpha and Omega of Organic Farming/Gardening. Compost, if ready to use, is cool, moist, and the consistency of moist chocolate cake. It will crumble in your hand.........I like to call it Black Gold. If you try to use Compost too soon it will continue to compost in your seed bed and suck up all the Nitrogen making your Plants turn light green and then yellow. If this happens add some Blood Meal or some other organic nitrogen source.