Taking us to Chelsea in 2007.
Live images in March from Melbourne & Chelsea in May.
Please tell your friends. No one else will.
Gardening Articles for
week ending 3rd March 2007
Written by Wally Richards. [Photo]
IMPORTANCE OF EARTHWORMS
We all like to have nice gardens with healthy plants and the only way
to ensure this state is to have a healthy soil-food-web. That means a
soil that is teeming with microbes, beneficial fungi along with many soil
creatures including big populations of earthworms.
The easiest way to determine that you have good healthy soil is by the
number of worms you see when the soil is opened up. No worms, in a moist
soil, means you have a problem and until rectified you will struggle to
have healthy plants and gardens. Note that I say moist soil because when
the soil becomes too dry, too wet or too cold you will be lucky to see
any worms, even if you do have good worm populations.
When temperatures drop or soils get too warm or dry, 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. It’s something like a hibernating
Once conditions improve to the worm’s liking up they come to work your
gardens for you.
There are 3500-4000 species of earthworms around the world and nearly
200 species have been identified in New Zealand. They are full of
calcium, protein, fibre and vitamins, making them a valuable food source
for many mammals, reptiles and fish. Earthworms vary in size, on average
from no more than 1 centimetre to about 3 metres in length. One of the
world’s largest earthworms, the Giant Gippsland Earthworm (Megascolides
australis), is found in Australia. It has an average length exceeding
1 metre. However, the longest recorded earthworm was a South African giant
rappi), measuring around 7 metres in length.
An interesting site to find out about worms and other aspects of gardening
is at hosted by Lincoln
The following is some of the information they provide on earthworms: Pastures
commonly support the biggest populations of earthworms as they usually
contain large amounts of organic matter and are infrequently disturbed
by cultivation events.
Numbers of earthworms can commonly range between 7 and 12 million per
hectare under a productive pasture in New Zealand. This corresponds to
1 to 3 tonnes of earthworms per hectare and means that the weight of earthworms
below a pasture is similar to the weight of the grazing animals supported
Earthworms are hermaphroditic, which means they each have both male and
It is an old wives’ tale that cutting an earthworm in half will make two
earthworms; one part may survive, but it is much more likely that both
parts will die.
The excreta produced by earthworms is known as casts. As soil passes through
an earthworm’s body, some of the nutrients are converted into forms that
are more readily available for plant uptake. So casts are generally rich
in plant-available nutrients like nitrogen, phosphorus, and potassium.
As well as consuming soil, earthworms also help to break down and thereby
recycle organic materials (such as dead herbage and dung). Scientists
have calculated that each year through their activities they are responsible
for burying around 6 tonnes of pasture litter per hectare.
As they burrow through the soil, earthworms create burrows and channels
that help to loosen the soil, allowing air to circulate and roots and
water to penetrate the soil more easily.
In New Zealand an incredible 25-30 tonnes of soil per hectare per year
has been measured by scientists as being deposited by earthworms on the
soil surface in the form of casts. But we must remember that some earthworms
deposit their cast material both within and upon the soil surface, so
the total amount of soil that they turn over in a year is even higher!
There are four main types of earthworms that you might find examples of
in your garden:
Compost dwellers. Like to live in high organic matter environments such
as compost heaps, but will not usually survive in soil unless it contains
very high amounts of organic matter.
Soil surface dwellers. Feed on decaying roots, shoots, leaves and dung
and live near the soil surface (0-15 cm depth). Important in mixing plant
litter into the soil.
Topsoil dwellers. Most common earthworms in New Zealand; live in the top
20-30 cm depth of soil. Burrow through soil, eating and excreting it.
Tend to eat more soil than organic matter.
Subsoil dwellers. Tend to live in permanent burrows up to as deep as 3
metres below soil surface. Drag food such as leaves into their burrows
from the soil surface. Often larger than other earthworm types.
What affects earthworms? Temperature (they don’t like it too hot or too
cold) Moisture (they don’t like it too wet or too dry) Food availability/type
(some sources of organic matter are of better quality/contain more nutrients
than others) Soil type and texture (soil organic matter is a good food
source; sand can be abrasive to the earthworm’s skin) pH of soil/organic
material (most earthworms prefer a pH closer to neutral) Seasonality (numbers
decline during summer when it gets hot and dry)
Land management (cultivation, fertiliser application, irrigation) Predators
(such as birds and flatworms) Toxic substances (such as fungicides, fumigants,
chemical weed killers, sprays and chemical fertilisers such as General
Purpose, Rose etc and Nitrophoska)
How do I encourage earthworms in my garden?
Maintain soil pH between 5.8 and 6.3 by adding lime periodically to the
soil. Limit the amount of cultivation where possible but, if cultivating,
avoid machines that pulverise the soil and the earthworms contained therein.
Limit the use of harmful pesticides etc as mentioned above.
Irrigate the soil during dry periods to maintain earthworm activity, and
increase organic matter in the soil (a good food source for earthworms)
by incorporating composted material and animal manures.
You can breed worms in a worm farm such as a Worm-a-Round (see ) I have
two of these units in operation and my well composted gardens are now
full of worms as a result. You simply put your kitchen wastes into the
worm farm to feed the worms and gain worms, worm pee and worm casts for
your gardens while turning your scraps into a valuable garden resource.
Liming regularly your gardens with a fast acting lime such as Rapid Lime.
(which I will be discussing in a few weeks time) Applying animal manures
and compost as mulches along with Magic Botanic Liquid as a soil drench
makes moist garden soils a paradise for big worm populations.
Cultivation of soil such as digging should be kept to a minimum and instead
cover bare soil with animal manures and compost (in that order) and then
plant your seedlings into the compost.
If you need to dig a garden to loosen the soil or to add in compost this
is best done when the soil is dry and the worms are not present.
Total avoidance of common fertilisers and chemical sprays is a must.
When plants are finished such as annuals and vegetables either cut them
off at ground level or pull out with the minimum of soil disturbance.
This also applies with weeds. Not only do these actions give minimal disturbance
to worms but it also leaves the webs of beneficial fungi in tack
to the great benefit of all other existing plants.
Problems ring me at 0800 466 464 (Palmerston North 3570606)
Web site www.gardenews.co.nz
Garden Pages and News at www.gardenews.co.nz
Shar Pei pages at www.sharpei.co.nz
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