Careful! Earthworms Underfoot
Worms Help Farmers With
A soil scientist
for the past 25 years, Dr. Dennis Linden knows a thing or two about earthworms.
Sure, he knows worms are good for gardens
and farmland. By tunneling through soil, they bring in oxygen, drain water and
create space for plant roots. Like many people, he also knows worm
casts (manure) are rich in nutrients.
Linden works at ARS
Water Management Research Lab in St. Paul, Minn. There, he is literally
unearthing important clues farmers can use to get the most from their
lands earthworm population.
Along the way, hes come across some
less well-known facts about these helpful creatures, such as how well they
adapt to different soils and temperatures.
Two good examples are species of
Aporrectodea and Lumbricus [say, Apor-wreck toadeea,
and Lum brick-us].
When temperatures drop or soils get too
warm or dry, these worms know what to do. If it starts getting chilly, they may
tunnel deep into the soil before it hardens. They may also coil into a
slime-coated ball and go into a sleep-like state called estivation. Its
something like a hibernating bear.
One winter day, Linden chipped away at a
frozen patch of soil to check on these slimy, sleeping
I found them curled up in a tight
little ball with a layer of mucus around them, says Linden.
Theyre very well adapted. Theyll survive in frozen or dry
soils by estivation and come back when conditions
Today's farmland is a favorite home
of worms whose descendents most likely came with European Settlers. Here, two
scientists try their hand at nabbing a modern day
This adaptability is one reason why
species of Aporrectodea and Lumbricus are the most common in
But it may surprise you to know that
neither are originally from this country. Scientists believe the worms probably
were brought here from Europe by settlers. Most likely they came with the
settlers in ship ballast, seed stock, potted plants and who knows what
else, says Linden.
Once in the New World, as it was called
then, these stowaway worms grew used to the new soils, climate and
plant life. And, they began to spread. In fact, scientists believe the
stowaways may have edged out native worm species from the choicest food and
One modern-day descendent is the
nightcrawler. Widespread throughout North America today, nightcrawlers are
among the countrys largest worms, reaching 8 inches or more.
They are also really fast.
Youve probably discovered this
first-hand if youve tried to nab one peeking out of its hole.
Nightcrawlers spend a lot of their time on the soil surface getting a snack. So
speed is important if they are to escape watchful birds and other hungry
Night crawlers are important to
agriculture. But is a bigger worm better than a smaller one, like the common
grey, when it comes to mixing soil or making more nutrient-rich casts for
Not in my opinion, says
Linden. I think it has little to do with the size of the worm. But
theres some disagreement on the topic, he adds.
Each species is different, he says, with
different strengths, weaknesses and roles to play in
Now, if youre going fishing, a
plump, juicy nightcrawler may be the way to go.
Linden admits to occasionally baiting a
hook with the hefty wriggler: Ive used nightcrawlers and
Agricultural Research Service, Information Staff