What’s in a word? Well, if it’s the word dirt or soil, it turns out, it’s a lot.

While most people, myself included, often refer to the stuff under our feet as dirt, it turns out, we’re wrong. Dirt is a common word used to describe ground that has created a mess. However, it lacks microorganisms and organic matter that is essential for plant growth and soil health. Think about it, when you grab a muddy puppy and wipe off its paws, the grime on your towel doesn’t begin growing grass.

Soil, however, is the Earth’s upper crust composed of minerals, organic matter, water, air and microorganisms. Bring in a pot of soil and leave it on the kitchen table and grass may begin to grow. That’s the difference. While we often think that soil is in endless supply, soil covers roughly 25% of the Earth’s surface, and only 10% of this soil can be used to grow food.

While it appears to be everywhere, what do we really know about the stuff under our feet? Soil consists of four main components: minerals (sand, silt, and clay), organic matter (humus), water and air. From there, soil can be further classified by particle size. For example, sand and gravel are considered coarse-grained soil. Silt and clay, which stick together, are considered fine- grained soil, and soil with a high percentage of organic matter is considered organic soil.

Soil includes six layers: the organic layer, topsoil, eluviation layer, subsoil, parent rock and bedrock. When I was a kid, I remember sitting in the field attempting to dig my way to the center of the Earth. I never quite made it, but boy, did I create a mess of dirt and rocks. Looking back now, even though I was sure I was halfway to the center of the Earth, I probably didn’t get much farther down than subsoil, if that.

Anyway, I digress. While those fancy names at the beginning of the paragraph are the actual names of the soil level, most scientists refer to soil layers, also called horizons, by their letters. The organic horizon is O, topsoil horizon is A, Eluviated horizon is E, B is subsoil, C is parent rock and R is bedrock.

Most soils have three major horizons; those are A (topsoil), B (subsoil), and C (parent rock) while some have O (organic). It turns out that the United States Department of Agriculture has a soil order that contains 12 different levels of classification. These classifications are the dominant characteristics of soils in a location.

Gelisols are permafrost areas, which are soils that are permanently frozen. Think of the Arctic and Antarctic; Gelisols comprise 9 of the world’s glacier-free land. Next is Histosols, which is composed mainly of organic material in the upper level. Bogs, marshes, peat lands, fens or mucks are considered Histosols and are saturated with water mostly year round. Drained Histosols can make great farmland, but they are not sustainable and will quickly wear out. Histosols are about 1% of the world’s glacier-free land. Spodosols find themselves next in line and this layer forms when rain interacts with vegetative litter, like pine cone needles. This type of soil tends to be acidic and has a low fertility rate; it occupies about four percent of the world’s glacier-free land surface.

Andisols soils form from volcanic material like ash and have the ability to hold both nutrients and water well, making these soils fertile and productive. These types of soils occur in areas with moderate to high rainfall and cool temperatures; they also have to be on slopes which erode quickly. This type of soil makes up about 1% of all glacier-free lands. Oxisol soils occur in tropical and subtropical regions and are dominated by iron oxides, quartz and clay minerals. These types of soils are found on old sloping surfaces and have low fertility, but can

be made fertile by adding lime and fertilizers. Oxisols are found over 8% of glacier-free land.

Vertisols are clary-rich soils that shrink and expand based on rainfall. When dry, these soils can form cracks three feet deep and several inches wide; when wet, they will expand. These soils are highly fertile, but can cause issues with building foundations, roads and even harvesting / planting due to their shifting nature. These soils occupy 2% of the glacier- free land surface. Aridisols occur in very dry climates;hence, the arid in their name. They are found in hot and cold deserts worldwide. They contain salt, gypsum and carbonates and make up 12% of the glacier-free land surfaces including some dry valleys of Antarctica. Ultisols are found in humid areas with a layer of subsoil clay. These soils are generally low fertility, but can be enhanced by fertilizer and lime. Ultisols make up about eight percent of the glacier-free land mass. Alfisols are similar to Ultisols, but are less acidic and more fertile. They are found under forest vegetation and make up ten percent of the glacier-free land. Mollisols are prairie or grassland soils that are highly fertile and continue their fertility due to the root systems of prairie grasses. These make up seven percent of the glacier-free land mass.

Inceptisols lack clay and occur over a wide range of parent materials and climate conditions; therefore, they have a wide range of characteristics. These make up 17% of the glacier-free land surface. Lastly, is Entisols which exhibit little to no soil development. This occurs when sediment deposit is faster than soil development; think active flood plains, dunes, landslide areas, and retreating glaciers. It can be found anywhere and is the second largest group of soils after Inceptisols at sixteen percent of the Earth’s surface.

Ohio has a diverse range of soils including: Alfisols, Entisols, Histosols, Inceptisols, Mollisols, and Ultisols depending on the region. Here in Northeast Ohio we live in an area that was glaciated; this means at one point we were covered by glacial ice. We live in the Eastern Ohio Till Plain and our soil is mostly medium textured soil with sandstone and shale fragments. Some areas have a high aluminum content which can increase lime requirements when farming or growing.

If you’ve managed to hang with me for this long, you’re probably thinking, great Christen, why do we care so much about soil? Well see, here’s the thing. The world has 36 billion acres of land. Only 4.62 billion acres are farmable. It takes anywhere from one to three acres to feed a person for a year. The population is around 8.2 billion. If we take the middle number and assume that it takes two acres to feed a person, we still need 16.4 billion acres to feed the world. We have 4.62 billion acres. We are asking 4.62 billion acres to do four almost five times the world it should have to. This means that farmers need to use safe and sound science to enhance the soil so that it can keep producing at its current rate and beyond for years to come. We can do a lot of things, but we haven’t yet learned how to make more arable land. So next time you’re out walking around or bemoaning the mud stops on your carpet; think about the fascinating world of soil that exists every day under our feet.

Clemson is a member of the Trumbull County Farm Bureau and completed her Ph.D. at the Pennsylvania State University. She and her family farm in Mecca.