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Subsoil Irrigation
Properly installed and set up,
irrigation systems can go a long way towards reducing our water use. These
systems basically fall into two types: overhead systems, where water is
sprayed over an area, and drip systems, where water is directed onto a
specific area.
Traditionally, overhead sprays have
been used on grass, while drips are used in flower beds and vegetable
gardens.
Obviously, these are good choices
for the vegetable plots and for dense groundcover type plantings…but what
about for grass?
For some time now, a number of
companies have been marketing drip lines for inserting under the soil. The
obvious advantages of this type of irrigation are that the water is directed
exactly where it is required (the roots), there is no water loss through
evaporation, there is reduced weed seed germination (the soil surface stays
dry), there isn’t a mass of unsightly hose on the surface and, relevant in
public areas, they are mostly vandal proof.
However, there are drawbacks.
Obviously, there is quite an expense in additional piping when comparing to
a sprinkler system and, unless installed prior to the final garden
construction, there will be a lot of upheaval required to install the pipes.
Other than this, my two main concerns have always been root intrusion and
lime scale.
The early subsoil drip lines relied
on weak weed-killer solutions being fed periodically through the system to
deter the roots of plants from entering. More modern systems now claim to
have emitters that do not allow roots to enter. Clearly this is a better
solution.
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As anyone with a standard drip line system will testify, lime scale build-up
soon restricts the water flowing out of the emitters. My previous enquiries
about this problem always brought the same response: clean the pipes through
with an acid solution. Without any clear guidelines, however, I was loath to
follow this route. It might be all right for putting through systems on a
vegetable plot when there aren’t any plants in the ground, but in an
ornamental bed?
As chance would have
it, I recently discovered an acidic fertilizer that has been specifically
developed for use through drip lines. Called "Novacid," it promises to not
only feed your plants but also to clean out the system. At last, a means to
safely clean out the pipes.
So, the final choice comes back down
to economics, as it does with so many other things these days.
Watch this space for
details of a textile sub surface irrigation system from Australia, which, it
is claimed, gives a more even coverage than drip lines, is less likely to
block and uses upto 60 percent less water than overhead sprinkler systems.
Flowering Now
This month I
would like to recommend the Victoria Rosemary (Westringia fruticosa).
As you will
gather from its common name, this is a native of Australia. The
second part of the name comes from the similarity in the way its small,
light coloured leaves grow in whorls, just like the common Rosemary. It is
tolerant of drought, and grows to about 1·5 metres.The most commonly seen
type has white flowers that are borne from spring until well into the
autumn. Look out for a pink flowering form that I have seen recently.
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