Sunflower and clay soil

I am interested in companion planting tuber or taproot forming plants such as sunflower. What are the benefits of annual sunflower planting to a soil such that tilth is improved? What are some best practices for planting and follow on to a season of sunflowers in a garden or field? Thanks. We particularly need this kind of function in the dry lands of Sudan.

Jeff, here is an interesting article I recently read regarding the benefits of growing sunflowers.