We dig in it all the time, but have you ever thought about what gives dirt its smell — or flavor?
I’ve written before about different kinds of the wonderful earthy stuff we grow plants in, and how some folks who insist it be called soil hold their noses when I call it dirt.
But good soils actually smell. Not talking about the low-oxygen stink of wet blue mud but the slightly sweet fragrance you get when you turn compost or smell a rain coming. It’s similar to catfish, mushrooms and freshly-dug potatoes. It’s also what gives drinking water taken from lakes and rivers a kinda skunky but harmless aroma and flavor during hot summers.
It’s mostly from an oil called geosmin that’s exuded by bacteria during dry periods. When raindrops hit dry soil, or as a low-pressure front ahead of a storm moves in and “degasses” the soil, small bubbles of geosmin float to the surface and release aerosols, which are called petrichor — which is what we smell.
Geosmin breaks down in acid conditions, which is why we use vinegar or lemon juice in many fish recipes.
Along those lines, a lot of old-timer gardeners could tell if their soil needed lime or not by touching it to the tip of their tongue to see if it was “sweet” or alkaline, or “sour” and acidic enough to need a little lime added.
It’s not as accurate as having a soil sample tested by the MSU Extension Service folks, but about as easy to figure out as the computerized agriculture-related recommendations that confuse average home gardeners. If you have your soil tested and need help converting to garden-friendly fertilizers, call the office number at the bottom.
Many people actually eat baked dirt. There’s an eating condition called “pica” in which people irresistibly crave strange stuff like clay, talcum powder and even charcoal, cigarette ash, spray starch, and cardboard toilet paper rolls. Dirt eating, also known as geophagia, is so common that researchers at the University Medical Center have studied it — a friend of mine from the New York Times came here to interview some Mississippi clay eaters.
There are well-researched benefits, including providing important mineral supplements lacking in diets, buffering against acids and tannins in acorns and certain other native foods, boosting immune systems and reducing diarrhea.
That last one is obvious; Kaopectate, an over-the-counter diarrhea medicine, is a slurry of chalky kaolin clay from Georgia. But before you go gnoshing on dirt, check with a doctor. Eating too much can cause digestive disorders and keep the body from absorbing iron, which can lead to anemia.
Dirt eaters prefer specific kinds of chalky-textured clay, found only in certain areas. And because they are usually bland and taste kinda earthy from the geosmin, after baking and breaking it into small chunks, most clay eaters splash on a little vinegar to add a bit of acidic tang which reduces the dirt flavor. I guess a true Southerner would try a little vinegar-based ketchup.
Last little esoteric item on dirt: In 2003 our legislators designated Natchez Silt loam, that band of tightly-packed wind-blown dust that gradually formed the loess bluffs and hills on the edge of the Mississippi River, as Mississippi’s official state soil. Really.
But before you make the easy leap from garden soils to how politicians are always trying to find dirt on one another, just don’t. There’s enough of both kinds to go around.
Besides, some of the latter kind of dirt can be hard to swallow, leave a bad taste or be just too difficult to digest. Stick with clay.
• Felder Rushing is a Mississippi author, columnist, and host of the “Gestalt Gardener” on MPB Think Radio. Email gardening questions to firstname.lastname@example.org.