Question: What’s your favorite soil?
Answer: You might just as well ask: Why in the world would someone have a favorite soil?? There are lots of reasons and lots of favorites out there.
Each state, for example, has a favorite soil that they name their State Soil. You can see them all in one place when the traveling soils exhibit, “Dig It! The Secrets of Soil,” opens again on May 1, 2014 at The California Museum in Sacramento, CA.
Or you can see pictures of their profiles at http://www.nrcs.usda.gov/wps/portal/nrcs/detail/soils/edu/?cid=stelprdb1236841.
There are a variety of reasons why a soil scientist might choose a favorite soil. It may be because it’s the dominant soil in the area, or it may contain evidence of the area’s natural history dating back thousands of years, or it may be an important part of a favorite landscape…..or it just may be a good-lookin’ set of layers, or “horizons.”
Iowa soil scientists, for instance, may favor the Tama series. It’s the Iowa State Soil and represents one of the most productive soils of the state. Or in the arid west of the United States, you can find very dry soils that have an accumulation of clay in the subsoil. The clay in the profile resulted when that soil was under a humid climate, not the desert environment you see today.
Personally I have two favorite soils. In the Brazilian Amazon, you can find soils called “Terra Preta do Índio” in Portuguese, which translates to “Dark Earth (soil) of the Indians.” These are soils that developed due to the action of pre-Colombian natives. The Indians modified the soil around their villages by incorporating their wastes into them for hundreds of years. Today these soils are high in organic matter and nutrients. The organic matter gives the soil a dark color that can extend down to at least three feet (Figure 1). Terra Preta soil also contains an abundance of broken pottery. It is one of my favorites because of the history it represents and the deep, black color that goes to such a depth.
My other favorite soil (Figure 2) is a very sandy soil with organic matter in the surface; a white, leached horizon below it; followed by an accumulation of organic matter; which is often followed by an accumulation of clay. These soils, when they are found in the Southeastern U.S., formed from ocean sediments. Their very sandy nature allowed both clay and organic matter to move down when excess rainfall percolated through the soil profile. We can produce something that looks similar in the laboratory in a short time, but these soils in the landscape took hundreds of thousands of years to form. They are among my favorites because of their unique colors and the arrangement of horizons.
Why not go to the above website and look at the great diversity in soil profiles? Better yet, plan to travel to Sacramento to see them in person. The Dig It! exhibit will be there from May 1, 2014 until March 29, 2015.
–Answered by Nick Comerford, University of Florida
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