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Earthworms and Healthy Lawns
Earthworms are normally not in sight, yet they reveal their hideouts to
those who look with an observing eye, or who search for signs through the
soles of their feet.
Along edges of lawns, especially, are their mounds or castings visible. A
close examination of these shows grass blades, leaves, and even small twigs
pulled part way into their burrows. A very careful digging alongside a
burrow to get to the bottom exposes plant material successfully pulled well
below the surface. The earthworm does not eat these grass blades, leaves,
and other plant material until they have been properly conditioned. Fungi,
bacteria, protozoa, insect larvae, and other minute organisms attack these
materials and slowly break them down with their digestive juices.
Thoroughly softened -- rotted, if you please -- these are taken in by the
earthworm to give it nourishment. To be exact, the earthworm gets not only
the decayed plant material, but the fungi, protozoa, bacteria and whatever
else was feeding on these, together with some soil.
When digestion is completed, the earthworm releases the wastes as castings
seen as little mounds. As one walks across a lawn, these mounds are readily
felt through the soles of one's shoes as bumps. Some people object to these
bumps in their lawns, and may proceed to apply arsenic or other poisons to
kill the earthworms. This also kills the protozoa, bacteria, and practically
all other organisms. These have been busy aerating the soil by their
burrowing and other activities. The soil becomes compacted, and a variety
of mechanical devices are then needed to aerate the soil and open it to
water percolation.
Several years ago, over forty school lawns were walked over. Two related
things were noted. On those lawns which the feet revealed had earthworms,
no trace of grass cuttings could be found, even though the lawn had been
cut just a day or two before. On the other hand, where there were no
earthworm hummocks, grass cuttings formed dense smothering mats, or thatch,
among the grass bases. In such situations, this thatch must be raked.
So, one has the option of learning the ecological fitness of the earthworm,
which through centuries was building soil, or setting up a situation which
is contrary to the ways of biology and ecology.
by Stanley B. Mulaik
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