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<pre>From my understanding phytophthora, rizoctonia & associated soil
diseases thrive in poorly drained soils. They can breed &harbour in
buried timber eg roots etc from past clearing works (they used to burn
the stumps out but now you need a heap of permits). I'm not too clear on
the soil drenches; do they kill all life in the soil? If so its likely
that more problems could appear.
There is an avocado farm nearby which was organic & grew quality fruit
on very healthy trees. The grower was a staunch advocate of mulching &
soil health. The property has since been sold & the new owner has not
followed the same regime & now phytophthora has claimed many trees.
There have been spectacular losses of another plant, english box or
buxus sempervirens. At a local builders display village they lost the
lot, must have cost 10s x thousands $. They are slow growing & closely
planted. Its my bet that as the buxus is native to the scrubby rocky
calcareous soils in the UK the heavy coastal acid soils plus summer rain
of Aust was too much, they had no resistance to the soil pathogens that
grew in that environment. In this respect olives share the same
requirements ie good that is very good drainage & alkaline soils.
This may be another reason why the greeks graft onto wild rootstock -
just as trifoliata is used for citrus.
The classic 'terra rossa' soils that some real estate agents like to
generously refer to are a red clay over limestone (eg clay 20-40% CaCO3
content 0-6% pH 6.7 to 7.3 over carbonate rocks). In Aust these regions
are noticeable when you enter, the bush is different. The ones that I am
familiar with are McClaren Vale, Coonawarra, Mt Gambier, Mt Barker. In
the Hunter casuarinas, ironbarks, melaleucas send out warning signs -
poor drainage, acid soils, stay away.
Another possibility is that just as boron deficiency can influence
fruit, leaf & wood development the same could be happening with the root
development. Its just that we cant see them. In Aust we are very low on
boron whereas in some parts of the Mediterranean there seems to be an abundance.


Roger Farquhar

[Non-text portions of this message have been removed]
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<pre>Roger,

I couldn't agree more with your overview.

It is all about learning the limitations of the natural systems in which we
live and farm. Any attempt at growing in conditions not ideally suited - and
there are many of these in Australia - is always fraught with some element
of risk of pest and disease and less than optimum production. (Remember that
mother nature will only nurture the strong!)

Organic and sustainable farming is about the systems approach to farming. It
is about learning the natural limitations and boundaries of each. The trick
is to find ways of integrating the farm system with the ecosystem so that
one is not at the detriment of the other. Obviously this requires a fairly
detailed knowledge of the two systems, with much research needed on an
enterprise basis before too many mistakes are made.

Always ask yourself what the pest or disease symptom actually means - what
is its likely cause and what needs to be changed to remove that cause? Don't
just react to remove the symptom - it is too short term a management
strategy and will need to be repeated over and again.

Taking a step back from the task at hand to appraise the situation, like
Roger has done, is vital for success.

Gerhard Grasser

"A man should farm as if he would live 1,000 years, but live as though he
were to die tomorrow."


----- Original Message -----
From: "Roger Farquhar" <rogfarlandsc@ozemail.com.au>
To: "OliveOil@egroups.com" <OliveOil@yahoogroups.com>
Sent: 25 August, 2001 8:09 AM
Subject: [OliveOil] soil diseases


> >From my understanding phytophthora, rizoctonia & associated soil
> diseases thrive in poorly drained soils. They can breed &harbour in
> buried timber eg roots etc from past clearing works (they used to burn
> the stumps out but now you need a heap of permits). I'm not too clear on
> the soil drenches; do they kill all life in the soil? If so its likely
> that more problems could appear.
> There is an avocado farm nearby which was organic & grew quality fruit
> on very healthy trees. The grower was a staunch advocate of mulching &
> soil health. The property has since been sold & the new owner has not
> followed the same regime & now phytophthora has claimed many trees.
> There have been spectacular losses of another plant, english box or
> buxus sempervirens. At a local builders display village they lost the
> lot, must have cost 10s x thousands $. They are slow growing & closely
> planted. Its my bet that as the buxus is native to the scrubby rocky
> calcareous soils in the UK the heavy coastal acid soils plus summer rain
> of Aust was too much, they had no resistance to the soil pathogens that
> grew in that environment. In this respect olives share the same
> requirements ie good that is very good drainage & alkaline soils.
> This may be another reason why the greeks graft onto wild rootstock -
> just as trifoliata is used for citrus.
> The classic 'terra rossa' soils that some real estate agents like to
> generously refer to are a red clay over limestone (eg clay 20-40% CaCO3
> content 0-6% pH 6.7 to 7.3 over carbonate rocks). In Aust these regions
> are noticeable when you enter, the bush is different. The ones that I am
> familiar with are McClaren Vale, Coonawarra, Mt Gambier, Mt Barker. In
> the Hunter casuarinas, ironbarks, melaleucas send out warning signs -
> poor drainage, acid soils, stay away.
> Another possibility is that just as boron deficiency can influence
> fruit, leaf & wood development the same could be happening with the root
> development. Its just that we cant see them. In Aust we are very low on
> boron whereas in some parts of the Mediterranean there seems to be an
abundance.
>
>
> Roger Farquhar
>
> [Non-text portions of this message have been removed]
>
>
>
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</pre>
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