Re: Protea and Iron

Mach T. Fukada wrote:
> 
> Aloha all,
>         been looking at some of the Protea (and related genera) that my MIL
> grows in Kula, HI and was noticing the interveinal chlorosis that seems to
> be indicitive of Iron defiency.  Any ideas?  I recalled that work on
> macadameia nuts indicated that they would show this sort of symptomology as
> a result of to much phosphorus.  I don't think this is the case here as my
> family rarely fertilizes and the soil is very high in Iron / aluminum
> oxides that normally tie up P in low pH conditions.  I need to know if I
> add Ca via dolomite or lime, will I adversly affect the plants by releasing
> high amounts off P?

Kia Ora

I have never heard of iron chlorosis appearing interveinally, it usually
just involves the whole leaf going yellow. The symptoms you describe in
my experience are usually a result of lack of MAGNESIUM.

Lewis Matthews,the NZ authority on proteas states in one of his books on
the family that high levels of both phosphorus and calcium are fatal to
them and their preferred pH range is between 5 and 6, so I would be very
chary about applying lime at any time.

Curiously, he doesn't mention lack of Mg as a problem, though he does
say they have been known to suffer from zinc deficiency. The symptoms of
this are however unusually small foliage, rather than chlorosis.

Obviously, if low magnesium is the problem, a dolomite application is a
possible treatment, if it can be done without unduely raising the pH,
but dolomite will also add more calcium, which could have disadvantages.
One could add magnesium without calcium by watering with a mag sulphate
solution applying about a tablespoon of the salt per bush dissolved in
plenty of water.

Yet another possible remedy,  which is one which NZ growers have used
with some success as a good safe food and booster, is a light mulch of a
well-balanced finished compost. If it is a well- balanced material it
should be able to deal with a mild incipient deficiency of most food
elements, but its trace element content could be enhanced with a small
amount of kelp powder (If seaweed was one of the compost ingredients
anyway, this should not be necessary)..

Moira
-- 
Tony & Moira Ryan <theryans@xtra.co.nz>
Wainuiomata, 
New Zealand (astride the "Ring of Fire" in the SW Pacific).
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