You can grow a cover crop to help build the soil. Plant a grain or legume crop, sometimes called green manure, for the purpose of chopping it down and adding it to the soil.
One way is to plant hairy vetch (Vicia villosa), a nitrogen-fixing legume, in your garden bed in the fall. In the spring, cut it down and till the residue into the soil. This provides both nitrogen and an instant mulch that preserves moisture.
I found the above article and video so I think I will try these around my tomato plants any thoughts?