DIANN JORDAN drove the flathead shovel into the ground with her
foot and pulled up a chunk of dry, black soil from a recently
harvested soybean field.
An earthworm poked its head out from the smooth side of the
hole, and Jordan gently pulled it out with her fingertips.
"Here's one," she said, lifting it and showing a visitor how to
identify the species among the thousands of kinds known to exist.
Jordan, a scientist at the University of Missouri at Columbia,
is studying the role that earthworms play in the complex
underground environment of soil, nutrients and water in Midwestern
The main site for the study is the Bradford Agronomy Research
Center, a farm that's part of the University of Missouri
Agricultural Experiment Station about six miles east of Columbia.
As Jordan and her colleagues dig there and in a few other spots
around the state, they are opening a kind of door on the inner
world of life beneath our feet.
It's a world that few of us think about, but scientists have
been studying it for a long time. Researchers know much about the
animals and plants that inhabit this underground world, but they've
only just begun to understand the ebb and flow among the ecological
links that connect these organisms and the environment.
The MU scientists hope the study will bring to light new ways
to understand soil quality and crop production. They also hope it
will improve our understanding of how pesticides and other
hazardous chemicals move through the soil - perhaps even into water
The researchers are studying the number, kinds and distribution
of earthworms under various farming practices. They're also
examining the ways worms change the physical properties of the
soil, including making vast networks of tiny tunnels.
"All that information comes together to make a complete story,"
Among discoveries so far, the MU scientists have found that
earthworms thrive in soil where they have a good food source from
crops aided by fertilizer. Worms also prosper where farmers
practice no-till farming, a method that basically leaves the soil
untouched by chisel and disk plows.
Charles Darwin, the 19th-century biologist most famous for
proposing the concept of evolution, once wrote that earthworms were
"lowly" creatures. But, Darwin added, "It may be doubted whether
there are many other animals which have played so important a part
in the history of the world."
For centuries, farmers, gardeners and others have associated
earthworms with healthy soil. But scientists know little about the
roles earthworms play in different kinds of farming methods.
Scientists split earthworms into three categories based on
where they live: shallow or deep in the soil or in plant litter on
the surface. Since the surface dwellers usually cruise through
leaves and other dead matter on the forest floor, they're rarely
found in farm fields. Shallow and deep dwellers are common in the
soil of Midwestern farms.
The deep dwellers, called nightcrawlers, can grow to 8 inches
long. A nightcrawler builds a burrow 5 or more feet deep and drags
plant residue down to it. The worm covers the top of its long,
vertical tunnel to the surface with plant pieces and waste. This
cap - called middens - serves as a food reserve and a protective
The shallow-dwelling earthworm plies the top foot of soil in
random patterns. This worm usually grows between 3 and 5 inches
long. Rather than building a burrow, it eats plant residue and
minerals along its trek. Shallow dwellers include the redworm,
grayworm and fishworm.
Earthworms are most active in the spring and fall. To escape
the heat of summer and cold of winter, shallow dwellers often dig
deeper than a foot, curl up in a ball and secrete a protective
fluid. Nightcrawlers simply escape to their burrows.
Earthworms improve the health of soil by leaving a wake of
nutrient-laden waste. …