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What is Soil?

What is Soil?

When most of us see soil we just see dirt. Soil is actually so much more than what we see. It varies from location to location, and season to season. Soil is vital to all life on earth.

So what is soil anyway? According to the United State Department of Agriculture Natural Resources Conservation Service “Soil is a naturally occurring mixture of mineral and organic ingredients with a definite form, structure, and composition. The exact composition of soil changes from one location to another.” The average soil in the US is composed of the following ingredients in these approximate proportions:

45% Minerals (clay, silt, sand, gravel, stones).

25% Water (the amount varies depending upon precipitation).

25% Air

5% Organic matter or humus (both living and dead organisms).

Soil is primarily composed of minerals. These minerals are formed by the breakdown of rocks. Over many years and in many cases centuries water, wind, and organisms break apart rocks into smaller and smaller pieces. Within soil you can find small stones and gravel, but most of the minerals in soil are found as clay, silt or sand. Sand are the larger particles which feel gritty when rubbed between your fingers. Silt is much smaller and feels like flour. Finally clay particles are the smallest and feel sticky when they are wet.

In between the soil particles are small spaces called pore spaces. These spaces are filled with water or air. The amount of water and air in soil is affected by many things including weather, compaction, and the amount of each kind of soil particle. Both water and air are needed in soil to support organisms living in the soil.

Finally, we have the organic matter in soil. Soil is filled with living organisms. Plants, bacteria, fungi, and animals all live in soils. When those organisms die they remain in the soil. These living and dead organisms compose the organic component of soil. The organic component provides nutrients to the organisms that use soil and helps to retain more moisture.

So why does this matter? First, if you would like to grow any plants, even a green lawn, understanding soil is important. Understanding your soils and how they are composed and created can help you choose the proper additions to your soil to help your plants grow.

Second, it is important for everyone to understand the role which soil plays in our lives and how long it takes for soil to be created. It can take over 100 years for just one inch of topsoil to be created. It can take one large rain storm on bare soil to wash it all away. Maintaining our soil resources is critical to our environment.

For tips on how to limit erosion please visit: pikeconservation.org/can-reduce-erosion-sedimentation/

Source: USDA Natural Resource Conservation Service “Soils 101”