A variety of soil types exist along the Gulf Coast. And, they are all somewhat different.
Gulf Coast Marsh Soils
Found immediately along most of the upper Gulf Coast, these soils can be divided into four types: freshwater, intermediate, brackish, and saltwater. Lakes, bayous, tidal channels and man-made canals crisscross the area. Most of this land is highly susceptible to flooding.
The soils are poorly drained, almost continuously saturated, soft and can support little weight. The organic soils contain a layer of thick, gray undecomposed organic material over a clay-like sub soil.
Coastal Saline Prairies
Covering over 3 million acres and extending from Mexico through Louisiana. Just at sea level or a couple of feet above, it also contains areas of salt-water marsh and drainage is slow. The water table is either at or just below the surface. Used mostly for cattle grazing, or wetland wildlife refuges, residents have developed wonderfully bountiful gardens by amending soils.
Spanning over 9 million acres and stretching through Texas, Louisiana and Mississippi, the coastal prairies range from 30 to 80 miles north of the Gulf. Even though surface drainage is slow, much of the soil includes dark-colored clays and loams. As most of us who live along the coast know, the topography is level and the soil amazingly productive. Rice, sorghum, cotton, corn, hay and sugar cane are major crops and productive home gardens abound through this area.
Alabama has coastal prairies as well, but little saline prairies and few coastal marsh soils. The Alabama coast, east of Mobile Bay, more closely resembles the upper Florida coast, with barrier islands, thin lines of beaches and then flatland forests inland.
Whichever of these areas you live in, you need to get your soil tested. See below for links to soil labs in each state:
There are some chemical properties you can determine on your own.
What color is your soil? Soil color reflects the amount of organic material, conditions of drainage and the level of oxidation and weathering of the soil.
Light-colored soil means low organic matter. Darker colors mean higher organic content. Also, light or pale colors of soil could mean courser soil and heavy leaching.
Dark colors can also mean high water tables and poor drainage (for instance the gumbo soil along the coast, or from the color of the parent material.
Red and yellow shades can mean finely-textured soil. It can also mean, as in the case of red dirt in Alabama and Florida, oxidized iron in the soil.
Red and brown subsoil show that there is free movement of air and water through the soil.
How coarse or how fine the mineral particles in the soil determine texture.
Sandy soils are generally coarser, while silt is fine, smooth and feels floury.
The finest soil particles make up clay, while loam has mixtures of clay, sand and silt, and also humus. There are different types of loam, each with its own characteristics: sandy loam (feels sandy and rough but has some silt in it; silt loam (feels smooth – like flour, when rubbed between your thumb and fingers); silty clay loam (feels smooth when dry – sticky and slick when wet but has noticeable amounts of silt in it; and clay loam (smooth when dry and sticky and slick when wet – there may be some amounts of silt and sand in it, but there is noticeably more clay).