The dirt on soil


The full article by Alison Pearce Stevens was originally written for Student Science

Soil is easy to ignore. We might notice it when gardening or playing outdoors. But even when we forget about it, soil is always there, everywhere.

Most of what we see are mineral particles that we recognize as sand, silt or clay. There’s also plenty of water and air. But soil also is alive. It contains countless fungi and microbes. They help recycle the dead by breaking down the remains of plants, animals and other organisms.

Scientists study these things every day. These specialized researchers get their hands dirty to learn more about the very important ways that soils help us. They think soil is so important that they named 2015 the International Year of Soils. Soil, they note, is not only essential for life but also plays a role in everything from flood control to climate change.

More than dirt
If you were to divide a soil sample into 20 parts, 9 parts would be made up of the stuff we think of as dirt: clay, silt and sand. These are inorganic particles, which means they come from non-living sources. A full half, or 10 parts, would be equally divided between air and water. The last part would be organic, made from dead and decaying organisms. The soil also would contain countless numbers of minuscule microbes, mostly fungi and bacteria.

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The dirt on soil