Re: Protea and Iron

At 4:29 PM 5/10/99, 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?

Mach,
        Do I remember from a previous post that you said local HI soils
were pH 6.5 or so?  The most likely cause of the chlorosis would be the
classic 'lime-induced chlorosis' that locks up iron, zinc and manganese
with assorted anions.   A few plants(e.g. lot of the Ericaceae's) will show
interveinal at pH's as low as 6.3.  OTOH I know nothing of Protea's pH
requirements and I may be completely off base here.

 I recalled that work on
>macadameia nuts indicated that they would show this sort of symptomology as
>a result of to much phosphrus.

There are several of these situations where excess amounts of one ion will
produce deficiency symptoms of another element but they're rare.  When it
comes to iron the most common problem is from excess manganese or zinc.
  There are some odd leaf patterns from very low pH situations(under 5.5)
in which some metals become toxic but I'm not aware of any that cause
interveinal chlorosis;  they are more like mottling, crazy patterns of
colors all over the leaf.


  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.

Most California soils (usually pH 6.8-7.3) show LIC despite good reserves
of iron, zinc and manganese.
The only other cause of interveinal chlorosis that I know of comes from
drift damage from the herbicide 2-4-D (and that's only with certain
species).


  I need to know if I
>add Ca via dolomite or lime, will I adversly affect the plants by releasing
>high amounts off P?

Not likely.  Max P availability is at pH 6.5 to 7.5.  But even at those
levels only about 1% of soil P is in solution.  I can't prove it but it
seems very unlikely that P would be responsible in your situation.
Jerry Heverly, Oakland, CA
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