The Rural Voice, 2002-04, Page 19Je. Pc
These Night Crawlers meet up to mate without leaving
their respective burrows. Worms are most active in
spring and fall when food and protection is more
readily available. Summer months are hotter and dryer,
placing the worms at risk of dehydration.
s
leaves of apple trees and
suyabeans.
So voracious are their appetites, that
these earthworms can completely
sweep clear the surface of a soyabean
field of its fallen leaves in just a few
short weeks. In fall, the entrances to
the Night Crawlers' burrows can
easily be recognized by the mounds
of leaves and plant material that form
as they drag any decaying litter,
within reach to their burrows (photo
on page 14). Removing leaf litter
from the soil not only increases the
organic matter in the soil, but can
also reduce the spread of fungal
diseases in crops, vineyards and
orchards by removing infected leaves
from the surface.
n exchange,,the earthworms
deposit fertilized soil at the
surface — casts, or pellets
composed of particles of soil and
undigested waste left at the openings
of their burrows. Earthworms feed on
bacteria, fungi, nematodes, and
decaying matter from both plant and
animal life. Earthworms will also
ingest soil while burrowing, mixing
the soil while gaining additional
nutrients. Remarkably, Earthworms
can consume up to one-third of their
own body weight in a day. In a single
acre of land, earthworms can recycle
10 tons of decaying material into
nutrient rich soil, thereby increasing
the availability of nitrogen,
phosphorous and other nutrients.
Deep borrowing worms like the
Night Crawler also bring valuable
minerals to the surface from great
depths that may otherwise never be
available to plant life.
Meanwhile, other species of
earthworms spread out and attack the
soil at different levels, each filling its
own niche with yarying tunneling
and eating habits. Garden Worms, or
Dug Worms (Aporrectodea
trapezoids, A. turberculata, A.
turgida) burrow continuously and
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1.4
randomly as they search for food in
the top 10 centimetres of soil. This
tunneling activity creates a large
network of horizontal and vertical
tunnels. These provide increased
aeration and water infiltration that
increases the availability of water and
oxygen to plant roots. In addition,
these networks of tunnels provide
channels for developing root systems
to follow and result in larger, deeper
and denser root systems. Burrows
and soil aggregates improve soil
structure, add soil stability and limit
erosion.
Earthworms can be considered an
important indicator of healthy soils.
If conditions are not to their liking.
earthworms will not be present in
large numbers — if at all. But where
there are earthworms, the soil is
likely more biologically diverse and
active. It is the Earthworms, together
with a host of other soil organisms,
which are responsible for the vast
majority of cycling of nutrients in our
soils, Earthworms can be
appropriately called ecosystem
engineers, building the soil and
impacting every living thing, from
other organisms in the soil to the
plant and animal life above.
Despite all that earthworms
I v.
contribute to our soils and crops. It is
the plow that is one of the worms'
worst worries. By destroying
earthworms and their burrows. tilling
markedly reduces earthworm
numbers — from potentially
hundreds of worms per square meter
in some no -till soils. to perhaps only
a few in conventionally -tilled soils.
Tilling also disturbs the surface litter
that feeds, as well as protects the
earthworms from heat and
dehydration. A study conducted by
Agriculture Canada at the Woodslee
Research Station in southwestern
Ontario. found that soils existing
under a no -till system for years had
an earthworm population of 170
individuals per square metre.
However. after only a single season
of conventional tillage. the
population in this same soil
plummeted to only 20 earthworms
per square metre. And perhaps more
surprisingly. when left unplowed the
earthworm population in this soil
required two or more seasons to
rebound back to their former
numbers.
While various tillage systems are
used or supported for various
reasons, it is important to recognize
how these alter, or create new soil
The wonder of worms
The Night Crawler, or Dew Worm (Lumbricus terrestris) is Canada's largest
earthworm species; the largest specimen recorded was nearly 30 centimetres
long and weighed 11.2 grams.
Earthworms usually burrow deeply to avoid freezing in the winter. The
deep vertical burrows of the Night Crawler can extend to a whopping 3
metres in depth.
Earthworm casts, or "droppings", may contain up to five times the nitrate.
seven times the available phosphorous, and 11 times the potash that occurs in
the surrounding, uneaten soils.
Large parts of Saskatchewan appear to be void of earthworms. Although
some farmers have reported finding worms in their wells. scientists still
haven't identified any earthworm species from the immediately surrounding
grasslands.°
APRIL 2002 15