By: Patrick Troyer, Education Specialist
So you walk on soil every single day, but how much do you really know about it? How does it form? What does it need to form? How do nutrients get in the soil? These are just a few questions that you likely have but there is so much more beyond this to learn about the ground beneath our feet. This week’s article will give you the “dirt” on soil so you will have a good understanding of how important of a resource our soil truly is in our lives.
Let’s first address where soils come from and how they form. Soils originate from parent materials which consists of rocks and minerals that have been broken up into tiny pieces through the process of weathering. During the weathering process, large rocks and minerals are being broken down or dissolved via natural agents such as water, ice, plants, animals, and temperature changes. Weathering will change the color, texture, and composition of rocks. Over time, large rocks are broken down into smaller rocks which are then broken down into smaller pebbles that are then broken down into the smallest particle possible, soil.
Exactly how long of a process is this? According to Soils4Teachers, it can take over 500 years just to build one inch of topsoil! Each time erosion takes place, years and years of hard work are being undone in the matter of just a few minutes. The way that soil forms will depend greatly on several different factors which include parent material, topography, climate, biological activity, and time. According to the USDA Natural Resource Conservation Service (NRCS), soil generally form from material that moved in from another location such as glacial till which is material that is moved and broken down by glaciers.
Climate has a big influence on soil formation. Warmer climates increase soil formation activity as warner temperatures will increase chemical reactions, biological activity along with moisture effectiveness, according to NRCS. Topography influences soil formation in the sense that more mountainous or hilly terrain will allow soil to easily be eroded compared to a flatter topography. Biological activity in the soil is continually developing the soil with the constant tunnels being made allowing for air and water to easily move through the soil and the decomposition taking place of decayed plant and animal material to allow for a recycling of nutrients. Lastly, we consider time as a factor of soil formation. According to the USDA NRCS, time for all the above facts to interact with one another also falls into play as soils will display features of the other formation factors over a longer period.
Now let’s talk about what makes up soil and the three different types of soil particles. Soil is made up of 45% minerals from rock, 25% air, 25% water, and 5% humus. Not sure what humus is? Humus is decayed organic material from deceased plants and animals which is a source of nutrients in the soil. Soil is broken down into horizons that are characterized on the presence of nutrients, soil, and rock particles. Among the major soil horizons, are the A, C, C, and R Horizon. The A Horizon is the layer where the topsoil is found and is made up of humus and other mineral particles, thus this is where a clear majority of soil nutrients can be found. Digging deeper, the B Horizon or “subsoil” contains significantly fewer nutrients and more rock particles. The C Horizon is made up of slightly broken up bedrock while the R Horizon is made up of hard bedrock.
Soil is made up of three types of particles which are sand, silt, and clay. Which of these would you think is the largest? Contrary to what most might think, sand is the largest of the soil particles, but which have large distances between them allowing water and nutrients to easily pass through. Clay makes up the smallest soil particle, but particles are closely packed together which allows for water and nutrients to be held for longer periods of time. Silt falls in between sand and clay as it shares properties of both. It feels smooth and powdery when dry and slippery when wet.
It is important to make mention of just how alive that our soils are. Soils are home to a wide variety of insects, worms, and bacteria who are actively working to make soils productive. Bacteria carry out most of the decomposition in the soil which allows a constant recycling of nutrients so they are available for plants to utilize. In just one teaspoon of fertile soil, there are between 100 million and 1 billion bacteria! Worms living in your yard, garden or farm field are a welcome thing to have as worms dig tunnels which helps to improve the ability of water and air to make its way through the soil.
An article on soil simply cannot be written without distinguishing between the terms soil and dirt. Soil is the proper term to be used when referring to the ground beneath your feet as it is the upper layer of the earth where plants grow. Dirt, on the other hand, refers to loose earth or a substance such as mud or dust that makes things unclean. Now you have the “dirt” on soil and can learn to appreciate the importance it serves in allowing us to feed and clothe a growing population. Stay tuned for part two of the soil series where we will cover ways we can protect this valuable resource!
