The Dirt on Soil Critters


They’re teeny-tiny and really, really hungry.

Careful where you step! Right under your feet, an invisible horde of hungry critters is working hard to keep trees growing tall, rivers running clean, and wildlife growing strong. Some critters eat leaves, while others supply roots with the minerals and water they need to grow deep. Other kinds of critters eat each other, and the whole hidden feeding frenzy maintains the world as we know it. Let’s grab a handful of dirt, put a pinch of it under the microscope, and Xplor the soil food web.

Meet the Microbes

They may be microscopic, but soil critters are huge in number. A handful of dirt holds more soil microbes than there are people on Earth. That’s a lot of life! This multitude of mini munchers also plays many important roles.

  • Bacteria and fungi break down bits of leaves and minerals so roots can absorb their elements.
  • Single-celled critters like amoebae, ciliates, and rotifers also help break down dead plants and minerals into particles that growing plants and other animals can use.
  • Nematodes (microscopic worms) play many different roles depending on what they eat. Root feeders attack roots. Nematodes that eat bacteria and fungi can help control the kinds of nematodes that harm plants. Some nematodes are predators, and they help control the root-feeding nematodes.
  • Mites and other microbugs can be shredders or predators. Shredders help bacteria, fungi, and other critters break down dead plants and animals. Predators eat shredders (and anything else they can overpower).

Make Room for Earth-Movers

Larger critters are also part of the soil food web, and they play an important role as earth-movers. Earthworms, ants, and moles all spend their lives tunneling or making chambers in the soil. These pathways let in air and water, which most life-forms can’t live without. The soil itself needs little spaces between its particles so water can soak in. After all, if water runs off, it takes everything with it, leaving behind nothing but ugly ruts and gullies.

  • Earthworms eat decaying plant and animal matter and poop out castings that enrich the soil. Their tunnels also let in air and water, helping stabilize the soil and supporting the food web.
  • Ants eat bits of plant and animal matter. Their tunnels and chambers are pathways for air and water.
  • Think moles eat plant roots? Think again. They’re strictly meat eaters, and they spend most of their time plowing through the soil in search of earthworms, grubs, and even small mice. If your mom hates Japanese beetles, tell her to give moles a break. They gobble up Japanese beetle grubs before they can grow up and eat her roses. Oh, and mole tunnels help air and water get into the soil, too.

The Soil Food Web at Work

The Producers

  • Plants use sunlight, air, water, and nutrients to grow and produce sugars and starches.
  • Roots exude a starchy fluid that activates fungi.
  • Organic matter is made up of leaf litter or compost.

The Clean-Up Crew

  • Bacteria help make nutrients such as nitrogen available to other living things.
  • Fungi help break down organic matter into minerals. They trade the minerals with plant roots in exchange for sugars.
  • Single-celled critters like amoebae, ciliates, and rotifers help decompose plant and animal matter.

Friends and Enemies

  • Nematodes are tiny wormsthat eat roots, bacteria, fungi, and even other nematodes.
  • Mites shred leaf litter and eat other creatures.
  • Earthworms, ants, and moles are earth-workers.

Play in the Dirt!

Soil Your Undies

You don’t need a microscope to see proof your soil is full of hungry critters. All you need is a clean pair of all-cotton tighty-whities. Bury them in the top 6 inches of your soil. Mark the spot and mark your calendar. In two months, dig up your drawers. If you find a few clean, white shreds, you’ve got a healthy soil food web. If your shreds are stained, your soil critters need help. Give them a thick layer of fluffy compost, and they’ll gobble it up before you know it!

Start a Compost Pile

Making compost is easy. All you need is a place to put vegetable scraps (no meat, bones, or grease), grass clippings, and leaves. Spray it with the garden hose during dry spells, and stir it with a rake once in a while. The microbes will do the rest. In six months to a year, you’ll have a heap of crumbly, earthy-smelling compost for your garden.

Dig Yourself a Happy Place

Scientists have found that breathing soil microbes while you play in the dirt makes you feel happy. It’s also fun, so get outside and start your spring garden!

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