Gulf Coast Dirt… (Soil!!!)

article by Steve R. Black

While attending the University of Florida in the 80’s my General Soils Professor (an ex professional football player with the Detroit Lions) forbid us from using the term “dirt” loosely. He taught our young minds that “dirt was just soil out of place.” Needless to say, this point of view has stuck.

Why am I telling you this? This is the point when I lose Shelley’s attention…

Along the Gulf Coast we mostly have soils classi ed as Entisols, which are young, undeveloped soils (sand dunes and not necessarily only on beaches) with no de nable soil horizons. Our soils that are classi ed as Ultisols, somewhat more commonly inland, are generally weathered and more developed with visually identi able horizons (not just sand, but usually with an orange/red clay subsoil). So, if you were to dig a large hole and view the soil pro le like you would looking at a wall, one would easily see the horizons that are parallel to the soil surface (if they are present). The orange/red clay is primarily due to oxidized iron. The tan/ brown color of the soil near the surface is primarily due to the presence of organics (decomposed living matter).

Our quartz-derived sand particles are considered large so the pore spaces are large. It is safe to guess that the sandy soil will not hold much gravitational water. If you may, think of a large box of soccer balls and then the same size box of golf balls. If you were to try and wet the surface of all the balls, the much greater number of golf balls with the resulting smaller spaces in between will result in a signi cantly greater amount of water held by the golf balls. Now you may be able to visualize the fact that as a general rule, a cubic foot of sandy soil will retain only about 1 inch of water that passes through the soil pro le as moisture. In contrast, our midwestern friends with their heavier silt and clay soil components will be able to retain 2-3 inches of water. That helps explain why our landscapes require irrigation along the Gulf Coast. In as little as a week, we can see our wet conditions from daily rain dry completely with an immediate need for supplemental water from irrigation. I frequently have clients that relocated from another part of the country that have a hard time understanding that even though it rained last week, their lawn seems to be in distress.

Why do we along the Gulf Coast have very little topsoil? Our native Forest Soils simply do not yield great topsoils. To be clear, it takes thousands of years for the earth to naturally produce topsoil. Some of the best producing soils in the world are ood plains of our rivers (like the Mississippi River). Think of it like this: throughout time whenever the river oods, this event occurs from heavy rain or snow melt upstream. These events produce more water than what the local conditions can absorb and this results into water runo . The resulting excess water that makes its way into our rivers is laden with whatever has diluted it with along its journey… organics, silt, clay, and more. The turbulence of the raging ood waters keeps the particles suspended along their journey. Eventually the resulting ood water is now sitting over the banks of the said river where the solids settle out. This happens over and over, and the deposit of the nutrient laden layer slowly builds an incredibly rich topsoil. These soils have a high organic and silt content and are teaming with microorganisms where plants thrive. There are other examples where incredible topsoils generate but, we will not go into that here.

Ok… trying not to bore you, but, if you are attempting to grow something in our soil along the coast this information may help you with perspective. Our incredible high rainfall amounts (~65”/year) coupled with notoriously sandy soils and our poor topsoils can present challenges. Couple these facts with our wind (there is a reason American Magic Sailing Team practices here) and sprinkle in a tropical storm event every so o en and welcome to my world. With the right knowledge and systems in place, there are successful farming operations, even olive groves, all around us. As we enter spring and attempt to acquire or maintain a beautiful landscape, we will need to be armed with a good fertility program and irrigation on-hand at a minimum. These components and possibly the help of a local professional will give you the best chance to yield a successful outcome.

Questions or comments? Email steveblack1986@gmail.com.

R. Black