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What's Eating My Undies?

by Lisa Blazure, Soil Health Coordinator, Stroud Water Research Center

Thanks for taking the Soil Your Undies challenge and burying a pair of cotton briefs in the soil! Now the waiting game begins and the suspense builds as you anticipate what you will find when you dig them up after 60 days. Hopefully, you’ll see that most of the underwear is gone. But what happened to it? That depends on how healthy the soil is.

Did you know that there are billions of microbes - bacteria, fungi, protozoa - in a teaspoon of soil? These soil microbes need to eat and breathe just as humans do. But what do they eat? Carbon. Carbon is a common element in all organic compounds, including cotton. So when 100% cotton underwear is buried in the soil, the worms and other critters see it as food.

Worms are often the easiest to find in the soil. Earthworms can eat almost anything, even cotton, but mostly have a diet of leaf litter and surrounding soil. Worms are essential for decomposing leafy material and cycling those nutrients into rich organic matter and natural fertilizer. As they eat their way through the soil, they excrete it out as castings, which have lots of microbes, nutrients, and biological glues that hold the soil together.

An acre of earthworms can digest 20 tons of soil in one year! Their tunneling activity improves soil aeration, porosity, and allows water to soak in quickly. The burrows also allow roots to easily go down deeper into the soil and get nutrients they could not ordinarily reach. In an acre of good soil, researchers have found more than 1 million worms and 1,200 miles of earthworm holes or burrows!

Springtails are insects found in abundance underground. Called springtails for the forked appendage that allows them to jump up into the air, these insects are typically only a few millimeters long. They live in leaf litter, compost piles, and lawn soils. Springtails eat bacteria, fungi, lichens, algae, and decaying vegetation, fertilizing the soil in the process. Under the right conditions, a cubic foot of soil may harbor 10,000 individuals, with millions found in a single backyard. With such high densities, these insects are important links in the ecosystem, recycling nutrients and breaking down organic matter in the soil.

Many types of fungi also live in the soil. One group is called saprophytic fungus and they decompose wood, leaf litter, and other organic materials including cotton. Have you ever peeled away the bark of a rotting log in the woods or stirred a compost pile, and noticed the white thread-like filaments? That is the fungus at work. Fungus is needed to break down the complex carbon chains in organic matter.

There’s also another group of fungi living in the soil called mycorrhizae fungi. This fungus attaches itself to plant roots and the plant feeds sugars to the fungus. Why would a plant do this? Because the fungus also helps to feed the plant. The mycorrhizae fungi build a vast, spiderweb-like network in the soil. This web network can find water and nutrients that the plant roots can’t reach. Crops and plants grown in undisturbed soils that aren’t plowed and tilled can tap into this fungal network and get the nutrients to grow into healthy plants.

Soils are also full of bacteria and predators, called protozoa, that eat the bacteria. Although bacteria can’t digest the complex carbon chains found in cotton, they can eat the simple sugars and carbon that leak out of the plant roots. They also feed on fresh plant matter and absorb the nitrogen into their bodies so that it stays in the soil. As the protozoan predators feed on the bacteria, this nitrogen is released and can be absorbed by plant roots and mycorrhizae fungi. It is natural fertilizer for plants.

Are you wondering how many of these organisms are living in your soil? Digging up the undies after 60 days will hopefully give you a clue. Stay tuned for another post that will share tips and techniques to support this complex underground world of worms, insects, and microbes! Healthy soils = healthy plants & animals = healthy people.


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