earthworms when no soil tillage is
applied, as there will then be more
available food in the form of plant
residue. Soil moisture, temperature
and quality food sources are extremely important factors to promote earthworm population
growth. Studies have shown that
crop rotation with legumes have a
positive effect on earthworm population growth as it provides quality
food sources to the worms. Soil pH
is a further important factor to consider as a low pH will lower the
worms chance of survival. Good
irrigation and drainage of especially
sandy and clayey soils, as well as the
addition of fertilisers and organic by
-products also help to make conditions favourable. Furthermore, it is
important to consider which pesticides are being used, as aldicarb,
carbaryl, carbofuran, clorpirifos and
methomyl are hazardous to earthworms.
Due to the role that earthworms
play in the soil, they are important
helpers to farmers. This is especially
applicable to conservation agriculture (CA) systems where soil is no
longer disturbed. Under tillage
these worms suffer and their benefits are greatly reduced. Reducing
soil disturbance is an effective way
to increase earthworms. The numbers of earthworms will increase
rapidly as soon as the soil conditions become favourable. In CA
practices more earthworms are consistently found, however their presence is limited to soils with moist,
cool conditions and will therefore
not likely be found in dry parts of
the country.
Earthworm populations can be increased by adding oilseed crops and
retaining legumes in rotations under
no tillage. CA farmers can therefore
use the number of earthworms in
their soils as indicator of their soil
quality. Through the incorporation
of CA practices producers can reap
the benefits of earthworm activity in
their fields.
The compost earthworm Eisenia fetida which is used for scientific evaluations of farming or degraded soil
as they are excellent indicators of pollution and soil changes. (Photo supplied)