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Experimenting with Soil Mixes - a formula to guide me

Posted by fortyonenorth (My Page) on
Wed, Feb 1, 12 at 12:39

I've experimented with container mixes in the past, but never in a scientific manner. Starting with the 5-1-1 I've generally adjusted it to suit my purposes solely according to "feel." Taking a step back, I'd like to approach it in a more deliberate manner. To do this, I've developed a rudimentary formula for establishing the drainage characteristics of a proposed variation. This is only meant to provide very general guidance.

Considering the main components (peat, pine bark fines, granite, Turface, perlite) I've assigned a numerical value corresponding to the relative drainage characteristics or each. Granite and perlite rate a 1 (most free draining), PBFs gets a 2 and Turface and spaghnum peat get a 3 (most retentive).

Using this formula, the drainage profile of the 5-1-1 mix is a 2. ((5*2)+3+1)/7 parts). The gritty mix also gets a 2: (1+2+3)/3 parts. A heavier mix, let's say just for example 2:1 mix of PBFs and peat would rate a 2.3.

I freely admit, there is a lot more to substrate components than this single factor. At the same time, it's quick and easy and provides a very general rule of thumb for experimenting.

Please, feel free to comment and poke holes.


Follow-Up Postings:

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RE: Experimenting with Soil Mixes - a formula to guide me

I like the way you thought about this, it may be arbitrary, but it certainly gives you an idea of what a mix will be like before making it.
Have you seen my well aerated soil formulas post? I think that taking this method and applying the method of using (ad/ab)sorbent materials to achieve diferent mediums, would be useful for tailoring mediums for specific needs.


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RE: Experimenting with Soil Mixes - a formula to guide me

Thanks for the comment Bob. I'll look for your post.


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