Appyt is right, you need to contact your local Department of Agriculture or Natural resources agent. The land needed can very by state and rainfall. Your in Atlanta which I think has been having a drought for the last few years. What you need during those times will be different then for normal rainfall years too.
The main thing if you wish to have a "hay meadow" area is to set it aside from your normal horse pasture. I used to have our place split into 3 sections. A dry lot, a warm season pasture and a cool season pasture and I only have 10 acres. I still buy my hay, its just cheaper to buy it from my neighbor than to pay someone to bale it, or purchase and maintain the equipment needed to bale it myself.
"Until one has loved an animal, part of one's soul remains unawakened..."
- Anatole France