Thank you, Penfold!
This is a very helpful comparison. Indeed, the Perlite and the Lava are closer
than I thought. I'd assumed that the Lava retained less moisture, but now I know better.
I have a couple bags of unopened red Lava (Scoria), as well as quartz (my granite substitute),
and I think I'll be doing some succulent re-potting in the next few weeks.

Grey pumice, red scoria, white perlite....

{{gwi:587144}}

Josh

Looks great, Josh. I wish I could find a local source of pumice and scoria like that, but around here there is no pumice, and scoria comes in big chunks. You west coast people have all the good stuff, and great nurseries to boot.

Thankyou , I have found a source of the ted Lava sand so I have already been using it because I thought it would be better than the perlite about floating away.

I wonder how expandable shale rates here? That also is available readily here in Texas. And I wonder if decomposed granite difers significantly from granite. That is cheap as dirt here. It is dirt just 20 miles to the west of me. If I find some time should do this test but probably I won't since my time is spare time is disappearing fast..

There is something about those ingredients that looks absolutely beautiful, doesn't it?

No wonder I love the way my soilless mixes come out after using these ingredients.
Adding that uncomposted fir bark adds so much more flavor to it all. I love these mixes for my succulents!

Mike

Does anyone have this water holding and capacity data for peat moss?

Westes

I do not remember seeing any; perhaps because most (not all) ppl do not use peat in mixes for succulents and are aware that it holds water for quite a while (unless hydrophobic). Perhaps you can test it for yourself? - I know you are aware of a thread by ewwmayo on the subject. Here are his instructions for testing:

Required for testing:

• Digital scale, preferably in grams.
• Clean and dry pots (4" is adequate, needs to have one drain hole).
• Dry and clean plastic tub that can hold pot + water.
• Enough dry soil mix to fill your pot to the brim. (Peat in your case)
• Duct tape to seal bottom of the pot.
• Water.

Steps for testing:

1. Weigh the dry empty tub.
2. Use a small piece of duct tape and seal the drain hole of one pot. It must be water-tight!
3. Weigh the dry empty pot.
4. With the pot on the scale, fill it with water and record the weight.
5. Empty the pot and dry it.
6. Fill the dry pot with your soil mix to the brim.
7. Weigh the dry pot with your soil mix in it.
8. With the pot with soil on your scale, fill it with water and record the weight. If the ingredients take some time to absorb water, you may need to wait a few minutes and top up the water to the top of the soil mix level.
9. Carefully remove the pot and put your dry empty tub on the scale.
10. With your pot over the tub, carefully peel a corner of the tape to let the water drain into the tub. If your hole is too big the mix will fall into the tub and skew your measurements.
11. Weigh the water drained with the tub.
12. Weigh the drained but still wet mix and pot.

Formulae:

• Total Porosity = weight of water needed to fill pot / empty pot volume * 100.
• Air Space = weight of water drained from pot / weight of water needed to fill pot * 100.
• Water Holding Capacity = (weight of water needed to fill pot - weight of water drained from pot) / empty pot volume * 100.
• I am sure you can also google other instructions.
• If you test, could you post results pls?
• • ETA:
    I found some data from sungro. They list following:
• Total porosity: 89 - 94
• Water holding capacity: 74 -77
• Air capacity: 12 - 20

@rina, I was probably not ambitious enough to do my own test, especially since I tend to hate peat moss. :) But talk about delayed gratification: after a lot of details on how to do the testing you supplied the data. Thanks :) Do you have a URL for that Sungro page?

A Turface test by user @ewwmayo shows Turface saturation (sat) at:
whc 52% / por 69% ~= sat 75%

The Sungro peat moss data shows peat moss saturation at:
whc 74-77% / por 89-94% ~= sat 81-83%

I calculated the saturation (sat) for peat as 74/89 and 77/94 to establish an approximate range. Was that supposed to be 74/94 versus 77/89, which would be a much bigger range?

So based on this peat moss looks like it has a similar saturation (sat) percentage with Turface. What are the aspects of peat that make it so preferable in the 511 mix? Is it holding onto the water longer?

I'm not sure I understand how to define water holding capacity (whc) in the data above, where peat moss appears to have an advantage. One website I read had these definitions:

field capacity (usually) ~= 50% of saturation = maximum water holding capacity of soil against gravity

permanent wilting point (usually) ~= 50% of field capacity

water holding capacity = water content between field capacity and permanent wilting point

Using these definitions, it is hard for me to understand this data since none of the whc data points are ever less than 50% of the saturation.

@rina in your formula above you have:

Total Porosity = weight of water needed to fill pot / empty pot volume * 100.

I do not have a direct measurement of the weight of the water needed to fill the pot. I have the weight of the water that drained from the pot. I could calculate the weight of the water that filled the pot as:

Weight of water-filled pot - Weight of pot with dry soil

Is that what you meant by "weight of water needed to fill pot"?

Westes

I am sorry for misunderstanding - those directions are from ewwmayo. I just posted part of his post and results from -THIS THREAD- . You may have read it.

1. I would think that you are correct - but re-read his Steps for testing (just above the Formulae)