Finding rainbows belowground
Soils are hidden rainbows below our feet.
One of the most profound things I learned about soils in my introduction to soil science course 7 years ago is that all soils aren’t brown.
I, like many, pictured fertile, dark brown agricultural soils when I thought of soil. Brown, crumbly, soil was the first thing that came to mind.
And really, before that class, I didn’t really even think much about soil , let alone consider that brown may not be the only color of soil that exists.
Surely if I had thought about it, I would have realized that I have experienced red desert soils, and various shades of brown (light brown, pale brown, tan, etc), but that was about the extent of my soil color knowledge.
My introductory soil science professor cracked my mind wide open when he first showed up photos of different kinds of soils. I remember thinking to myself, “wow, I had no idea soils could be so beautiful…”
Since then, I’ve become obsessed with the many colors of the soil rainbow.
There’s a reason we talk about soils (plural), not just soil (singular). “Soil” assumes a homogenous entity. In reality, there are many different kinds of soils. There is a lot of heterogeneity belowground, especially when it comes to soil color.
The complexity of soils is well illustrated by the diversity of colors into which they form. Soils are dynamic systems that consist of interacting physical, chemical and biological components. These interactions lead to chemical reactions that change the color of soils.
Soils turn a deep red when iron is exposed to oxygen and oxidized. Soils fade to gray under saturated conditions where the lack of oxygen creates conditions for iron reduction.
Soils bleach white under dense pine forests where rain and organic acids from the needles leach the organic matter, iron and aluminum oxides and clays from the soil, leaving behind an enchanting layer of white.
Dark soils mix with lighter soils when organic material is buried beneath freshly deposited soil.
Soils can be green when derived from serpentine parent materials.
Soils that are exposed to air after many years of accumulating lake sediment oxidize to a light pink.
Yes, pink soil exists! In fact, you can find the entire rainbow of colors in soils. Dig deep enough and you won’t be disappointed.
Color is one of the great connectors of the human experience. We all see and experience colors. Many of us have a favorite color that brings us joy. Colors bring people together. Colors can also bring us closer to soil.
Soils are nature’s art palette.
Once you see and experience the beauty of soils, you can begin to appreciate them for more than just a medium for plant growth. You will begin to see them as essential living systems waiting to be explored.
