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<pre>Once upon a time....

somewhere or other I came across some figure which indicated the amount of
water an olive tree can expect to use at various times of the year. I have
no idea if these figures were on this group, in a magazine (which one?) or
in book (so many to pick from!!) but I am trying to estimate how many trees
I can support with an annual rainfall of 600mm, summer dominant. I have some
supplementary irrigation available, but I have a feeling that we have too
many trees for the available water.

Does anybody have a figure for young (up to 2m high) and mature trees?

Regards,

Mike Wilson
Hunter Valley.
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<pre>Mike,

The Californian Manual suggests that a mature olive tree is likeliest to
reach its maximum production capacity if it receives 1000mm a year. As the
olive is a Mediterranean tree it probably prefers to receive its rainfall in
a pattern as close to that in the Med as possible. Olives Australia's web
site contains rainfall patterns for many areas in the Med but in short, wet
autumns, cold, damp winters and wet springs followed by dry summers.

Yours,
Dan
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<pre>> Mike,
>
> The Californian Manual suggests that a mature olive tree is likeliest to
> reach its maximum production capacity if it receives 1000mm a year.

Thanks Dan. This is my line of thinking:

On the assumption that trees are planted 8m x 5m, giving 40 sq m per tree
and that whole area filled with roots, a mature tree will require 1000mm a
year rainfall (as above). As 1mm or rain is the same as 1 litre per sq m,
this means 40,000 litres per tree per year?

If rainfall is only 600mm per year, supplying only 60% of the total water
demand, rain will only supply 24,000 litres, so 16,000 litres will be
required as irrigation.

If the tree is only small, a 2 year old with a height of about a metre with
a root area of around 4sq m, then the rain falling outside the root zone is
of no consequence, and only ten percent of the rainfall can be considered as
effective. Rainfall at 600mm would supply 2400 litres a year.
This would require 1600 litres of irrigation which is obviously too much as
the smaller tree would transpire less, so again using a factor of 10, 160
litres of irrigation water per young, growing tree per year. The factor of
10 is debatable.

My concern is to not plant too many trees for the available water supply,
and I suspect we may have to cull some of the weaker trees is an already
planted block to allow enough water for the others to survive. The soil is
clay loam, so water running through the soil profile is not an issue.

Any comments on this set of wild assumptions would be valued.

Regards,

Mike Wilson
Hunter Valley.
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<pre>> Dear All
>
>
> Growing olives outside of mild wet winters and long hot dry summers
> increases the risk of problems - tree damage, fruit damage, stress,
> disease.
>
> ie production becomes marginal - and commercially less viable.
>
> The olive grows well and is productive at rainfalls of 600mm. The
> equivalent of 400mm ie 4megalitres/ha in the hot months tree reduces
> stress. If this level of irrigation is not available then around 1
> megalitre in the Jan/Feb (Aust) or NH equivalent is beneficial.
>
> Stan Kailis

Stan,

I assume these figures are for mature trees planted 250 to the hectare?

Mike.
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<pre>Mike,

First and foremost I am not a horticulturist and the fact that my trees
continue to survive and thrive (mostly) is always a pleasant surprise to me!

I can't fault your simple arithmetic. I am not certain if your estimates
of tree root area are valid, however, if you have overstated the requirement
based on root area it can only help to ensure that you have reserves of
water if rainfall does not measure up to expectations. It certainly
hasn't in the South Burnett for many years. I have seen suggestions that
the root area roughly matches the area shaded by the foliage.

The other problem lies in the timing. In SE Qld we are supposed to get
summer rain but the trees don't want too much at that time of the year.
Our winter is dry and a lot hotter than winters in the Med so I have to
provide quite a lot of irrigation water in the winter. I found that out to
my cost when I split the bark of young trees in cold weather due to having
insufficient water available.

Leaving aside, temporarily, the question of root area may I suggest that you
overlay your rainfall pattern with that of the Med and then make an
allowance for the difference in temperatures. How much allowance? To get
a clear picture of the rainfall pattern I reduced the monthly figures to
percentages of the total. The whole thing seems to be a bit of a guess.
Perhaps someone out there who is much cleverer than me will offer you some
thoughts. I see that Stan Kailis has posted a reply, possibly to you,
which might help.

Finally, what do others in the Hunter recommend?

Yours,
Dan
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<pre>Mike,
I saw a figure of 4Ml per hectare. In practice I am watering my trees on hills
soil (contains some clay so water retention is good) at the rate of 35litres
every 2 weeks. Trees are 1 year in the ground. You can also check the leaves and
also the sol to see if you are doing ok. But I guess you want to plan rather
than check existing trees.
Our rainfall is around 800mm per annum in the wintermonths mainly.

Hope this helps along with the rest of the responses you are sure to get.
Best Regards
Andrew & Val Brown

Mike Wilson wrote:

> Once upon a time....
>
> somewhere or other I came across some figure which indicated the amount of
> water an olive tree can expect to use at various times of the year. I have
> no idea if these figures were on this group, in a magazine (which one?) or
> in book (so many to pick from!!) but I am trying to estimate how many trees
> I can support with an annual rainfall of 600mm, summer dominant. I have some
> supplementary irrigation available, but I have a feeling that we have too
> many trees for the available water.
>
> Does anybody have a figure for young (up to 2m high) and mature trees?
>
> Regards,
>
> Mike Wilson
> Hunter Valley.
>
>
> @@@@@@@@@@@ >> Spread the knowledge! << @@@@@@@@@@@@@
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<pre>Dear All


Growing olives outside of mild wet winters and long hot dry summers
increases the risk of problems - tree damage, fruit damage, stress,
disease.

ie production becomes marginal - and commercially less viable.

The olive grows well and is productive at rainfalls of 600mm. The
equivalent of 400mm ie 4megalitres/ha in the hot months tree reduces
stress. If this level of irrigation is not available then around 1
megalitre in the Jan/Feb (Aust) or NH equivalent is beneficial.

Stan Kailis
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<pre>Congratulations Mike - this is one of the more intelligent questions posted to
this group.
Like you I find irrigation rates depend on what "expert" you talk to and
whatever you do never ask an irrigation supplier!!
My understanding is like Dan's that the root system area matches the foliage
area shading. On that basis on my 7000 trees and with 500-600mm rainfall I am
going to need to supply 33,000,000l of water per annum.
Buy shares in the Sydney Water Board fellows.
Is the figure of 1000mm per tree relevant to olive oil production combined with
RDI???
Stan Kailis - where are you?
Regards
David Wilson (no relation to Mike)


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<pre>Dear all

The information that I posted was for mature trees. 200-350/Ha. Young
trees require about 20 litres/week over summer to reduce stress. In dry
winter conditions similar amounts are required.

Stan Kailis
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<pre>The figures of irrigation quoted for different world regions can only be
a guide only; the water requirements of your own plot could be quite
different. Influential factors include the rate of evapotranspiration
(ie loss by wind, sun), the depth of growing medium, the water holding
capacity of that medium, the style of irrigation (overhead, drip,
sprinkler, flood), cover crops, the quality of irrigation water, the
degree of the development of the plants root system. Take
evapotranspiration, which is normally calculated with an open pan
containing water left out in the open with the loss of water measured
daily. In NSW I have seen two nearby sites, 1 at Richmond Air Base & 1
at Hawkesbury Ag.(now UWS) with differing measurements for
evapotranspiration, probably due to the variation in microclimates.

I think the best method for irrigators would be to instal some sort of
soil moisture measuring device(s) to determine your own site
requirements.

Roger Farquhar

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