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<pre>> My last independent soil test revelealed a slight Boron deficiency.
> Based on the recommendations in the report I calculated that the
> amount of Borax my soil required was 5 g per sqaure metre.
>
> I seem to remember the last time I flicked through the Olive
> Production Manual they were recommending adding 500 g per tree in
> similar circumstances. I think I also read the same figure in a
> report from a group of growers in the Hunter Valley in here in
> Australia.
>
> 500g seems like a hell of a lot of Borax. I was under the
> impression that Boron has a very small range between effectiveness
> and toxicity.
>
> At the same time I do want to make an meaningful difference to my
> soil Boron levels as my trees do drift in an out of Boron deficiency
> when I do a leaf test. I have used Solubor foliar sprays as a short
> term remedy.

Hi Steven,

I was probably one of the Hunter Valley group looking at Boron deficiency.
It was well known in the local vineyards that the local soils are boron
deficient, and we have found the same sort of thing with olives. Boron is
deficient below 19 ppm and excessive / toxic over about 185ppm (from
memory - please check these figures) so there is a fairly wide range, but
I've never heard of borax toxicity in Australia. I normally aim for around
40 - 60 ppm from a leaf test. Beware the residual boron traces after a
foliar spray, as this will seriously distort the figures. It can take a full
year for all the spray to be absorbed or wash off (especially with our lack
of rainfall).

The two chemicals - Borax and Solubor - work differently. Borax as a dry
powder is thrown around under the trees and takes a while to work its way
into the soil and down to the roots, especially here in clay-loam soils. We
put on 500g per tree to give it about a 5 year supply, as the tree will take
up what it wants if it is used this way.

Solubor / Bortrac are foliar sprays and are absorbed directly and very
quickly into the tree and used up fairly quickly. Ideal for a "top-up" just
before flowering but not really a remedy for boron deficient soils.

Depending on the usual variables : soil type and the ability of borax to
move through to the root zone; age and size of trees; tree spacing;
irrigation system; rainfall; availability of chemicals; budget etc there are
a whole host of options, but I'd be inclined to have a chat to a local
agronomist / soil specialist before doing anything further. $100 spent
talking to somebody with relevant experience will be quickly re-couped in
not wasting chemicals and time.

Regards,

Mike Wilson
Hunter Valley.
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