Re: Protea and Iron
- To: m*@ucdavis.edu
- Subject: Re: Protea and Iron
- From: J* A* <j*@nemo.mech.eng.usyd.edu.au>
- Date: Thu, 13 May 1999 10:34:31 +1000 (EST)
At 07:38 12/05/99 -0400, Xavier wrote:
>I have no references readily at hand, but I have rarely read anything on
>Australian Proteaceae without the author mentioning the toxicity of
>phosphorus.
However, this is true only of those protaceae which normally grow in
low-phosphorous soils (most, but not all of them). Australian rain-forest
soils are not phosphorous deficient. There are quite a few australian
protaceae which are rain-forest trees. Silky oak, Grevillea robusta, is the
most widely seen of these in gardens, in part since it is so easy to grow in
just about any soil. Macadamia is another. Rain-forest protaceae, like
other rainforest plants, respond well to fertilizer, including fertilizers
containing phosphate.
>Of course, I am not saying that excessive phosphorus is the cause of the
>yellowing foliage in Mr. Fukada's macadamia nuts. However, in view of
>the toxic effect of phosphorus on Australian Proteaceae, it should not
>be discounted as a possibility.
I think it very unlikely. I wouldn't be surprised though if, like others
seem to be implying, Mach's soil is a bit too alkaline. A pH of 5-6 is
appropriate for most of these plants.
John.
