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Digging in the Dirt

PISCES Mini-Lesson, Day 4: Earth, Soil, and Dirt

Photo 1: Drawing of a humus molecule by @caylalockwood based on image by Soil Secrets LLC.

Photo 2 and 3: Dirt versus soil in soil tests. The soil on the right is from our fields. It is healthier, darker, and smells better.

Photo 4 to 6: Hold the soil, smell the soil!

Earth: the stuff beneath our feet. It gets under our fingernails and stains our clothes. We put lots of resources into paving it over to make streets, parking lots, and sidewalks and then go to garden centers to buy expensive bags of it for our lawns and gardens. But what exactly is it? Believe it or not, but there's actually a difference between dirt and soil; dirt is dead and soil is alive. Both are composed of the same materials: sand, silt, and clay, but soil is teeming with plants, animals, and micro-organisms that drastically change how it behaves. A healthy soil will retain water, cycle nutrients, and provide spaces for roots to grow, all of which are super important to grow abundant, healthy food. The difference between dirt and soil is oftentimes rather stark; the former is often reddish and compact whereas the latter is dark brown or black and smells earthy.

So what makes this big difference then? A large part of it is something called Soil Organic Matter (SOM), or all of the stuff that's alive or was previously alive and is now in various states of decomposition. All of the dead leaves, twigs, and insect exoskeletons on the forest floor eventually break down and, as they are incorporated into the soil, become SOM. One very important component of SOM is humus, not to be confused with it's two “m” counterpart hummus which is a delicious snack. Humus (one “m”) is the dark crumbly stuff that you can find under the leaf litter in a forest or in a healthy garden. It is composed of large, complex, and somewhat chaotic molecules made up predominately of carbon, nitrogen, and oxygen. It has been theorized that, like snowflakes, no two humus molecules are the same and they come together to form messy aggregates full of nooks and crannies. It is within these little pockets that nutrients are captured, water is retained, and bacteria live, thus allowing the soil to sustain plentiful life!

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