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<pre>This I'm sure is the most preplexing question that we have had to
consider at our grove in York, Western Australia. We have a true
Mediterranean climate, with long hot dry summers - usually no rain at
all from November to March or April. I'll try to share with you a
little of what I have learned from the extensive research that I have
done on the subject.

Yesterday we attended a conference in Northam WA, at which an
irrigation specialist conducted a quick survey around the room to
find out watering regimes on different soil types within Western
Australia. Watering schedules ranged from 35 liters per day per tree
on sandy soil to 10 liters per week on gravelly clay soil. The main
factors that affected the amount of irrigation seem to be :

1. Soil Type - ie the water holding capacity of the soil which is
influenced by the amount of organic matter present.
2. Evaporation - climatic factors come into play
3. The age of the tree ,the size of the canopy, and the root spread
4. Water quality - some people are using very salty water, which has
another influence.
5. Delievery method - drips or sprinklers
6. Availablility/cost of water. Although no one mentions this very
often, I think it plays a part in the overall equation. How much
water do you have, and how much can you deliver to your trees in an
economical fashion?

As Australia goes further into drought the use of bores is being
considered by government - and we dont know how long we will be able
to use ground water without paying for it. I am sure that this will
affect the amount of water delivered to each tree, and perhaps even
cast a shadow over some of the large groves that irrigate heavily
with bore water.

We all know that olives will withstand very dry conditions. In my
opinion in the end it becomes a rather delicate balancing act of
economics - how much water do we need to give the tree to get the
optimal fruit production , or how little can we get away with? If
water is available in unlimited supply you have no problems - buy a
few fancy soil moisture measuring devises and water as required. If
water is expensive or in short supply, water enough to keep them
alive.

Not a very satisfying answer, I'm sure, but there are so many
variables there is no "right" answer. What do your neighbours do?
That is a good place to start, and then as we say in Australia -
"suck it and see !"
Good luck.

Meryl Widenbar
Merlins Grove
York, Western Australia
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