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Re: [APD] peat in substrate

----- Original Message ----- 
From: "Steve Pushak" <teban at powersonic_bc.ca>
To: <aquatic-plants at actwin_com>
Sent: Friday, March 05, 2004 3:33 PM
Subject: RE: [APD] peat in substrate

> Quintin Holmberg asked:
> > the plan for
> > the substrate is to use a layer of peat then profile then
> > gravel.  ...
> > how much of a layer of peat should i put?
> > should i mix the peat with some profile or just have a 100%
> > peat layer?
> Peat has a number of useful characteristics. With regard to layering,
> the important consideration is for peat to provide an oxygen sink to
> support reduction processes. This means that bacteria slowly decompose
> peat & consume oxygen. This allows manganese & iron in the substrate to
> reduce thereby dissolving & becoming available to plant roots. Its best
> for the peat to be well mixed with a fine mineral component such as soil
> which contains the iron minerals. This promotes contact of peat &
> mineral soil particles. Therefore its best not to create a layer of
> peat, but rather to mix it well with soil. I'm not talking about potting
> soil; I mean the ordinary dirt you find in the back yard. Potting soil
> may already contain more organic material than you want & probably
> contains compost materials that have too high an oxygen demand and decay
> to release too much nutrients for practical purposes (at least in my
> opinion). In systems without CO2 injection, such as Diana Walstad's
> approach, potting soil may work better as a source to provide CO2 by
> decomposition. Peat might provide some CO2 but it probably decays too
> slowly to provide enough CO2 to meet the requirements advocated by Tom
> for a high carbon & nitrogen regime. Remember that Diana also uses
> relatively lower lighting levels & this may be one of the reasons her
> approach works well.

laterite? i have seen references elsewhere to the usage of laterite for this


> I haven't read any qualitative descriptions of Profile except what Tom
> Barr wrote about it. I believe he described it as a highly porous
> material with relatively large grains. Similar porous materials like
> vermiculite tend to float and therefore need to be soaked in water for a
> week or two before they will sink. Since Profile probably sinks
> immediately, I have doubts about its texture & bioavailability of
> nutrients. If somebody in the Vancouver area has some Profile, I'd like
> to take a look at it & we could even run some simple tests to see how
> much iron it solubalizes. The idea would be to mix some with about 5%
> peat by weight in a sealed jar of water & then test iron levels after a
> week.

i have not yet used it either but, my understanding is that although it will
not float, it is very light and needs to be weighed down with a layer of
gravel or sand.


> Steve in Vancouver where the sun is playing hide and go seek with the
> clouds but spring is definitely well under way.

i sure wish it was here in minnesnowta!!

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