Water-retaining inorganic soil components?

[zeejet]

I've been using a mix of pumice, lava, fir bark (all 1/8"-1/4" sifted), and a bit of peat moss for all of my plants in development/growing. I've tried mixes without the peat moss and they do not seem to stay moist despite the uniform small particle size (need to water twice a day even in spring).

I want to move away from the fine organic components and do not want to spend the money for akadama. Are there any alternative inorganic substrates with good water retention (or more accurately, good water availability to the roots without compromising drainage or aeration)?

I've read a lot of mixed reviews on DE and turface (calcined clay) - Ryan Neil seems to like DE and zeolite/chabasai but hates turface (holds onto water but does not readily give it up to the roots) - I've also heard that these products are wildly inconsistent and still not particularly affordable.

 

[WNC Bonsai]

I know you asked for inorganics but you might increase your percentage of fir bark or use coco coir. Eric at Bonsaify has been mixing both in his basic soil but he is in San Francisco.

 

[roberthu]

Pumic is a good water retaining aggregate

 

[penumbra]

I've read a lot of mixed reviews on DE and turface (calcined clay) - Ryan Neil seems to like DE and zeolite/chabasai but hates turface (holds onto water but does not readily give it up to the roots) - I've also heard that these products are wildly inconsistent and still not particularly affordable.

I was really excited over DE a few years back, but it dries fast and so thoroughly that it literally hisses when you water it. I have heard some people really love it, but for me, I have almost stopped using it except where I want an arid mix like for my succulents. Turface has its problems in that it packs due to its flattened particle shape, but adding a bit in a mix is not a bad thing. I use it in mix for grow boxes. It is true that these products can be inconsistent.

 

[Eckhoffw]

I was really excited over DE a few years back, but it dries fast and so thoroughly that it literally hisses when you water it. I have heard some people really love it, but for me, I have almost stopped using it except where I want an arid mix like for my succulents. Turface has its problems in that it packs due to its flattened particle shape, but adding a bit in a mix is not a bad thing. I use it in mix for grow boxes. It is true that these products can be inconsistent.

Yep. I use sifted DE and Calcined clay. -oil dry.
I mix it with lava and pumice. All equal parts.

 

[Igor. T. Ljubek]

Zeolite (in various forms and colors from white to brownish, from natural zeolites to industrially produced such as zeolite chabasite) holds about as much water as akadama. It is much cheaper than akadama, but it is not easily available in the desired granulation: the particles are usually too small (rarely too large), sometimes even crushed into powder. Nevertheless, at least in Europe, zeolite with suitable particles can be found. It also usually has a more alkaline ph.
Then there's vermiculite, which isn't supposed to be the best substrate for bonsai. At least I haven't heard of anyone using it, although it holds even more water than akadama. But it also falls apart just as quickly. In any case, pine or fir bark or coconut fibers are better alternative than vermiculite imo.
Broken brick is also not the worst choice, but it is definitely the cheapest choice... It holds quite a lot of water. I used to break bricks with my own hands with a hammer, because years ago in our small country we did not have modern bonsai substrates with the exception of the not-so-popular perlite and vermiculite.

 

[Gabler]

For deeper pots (i.e. training pots), I've been mixing coconut husk chunks with perlite at a ratio of about 1:3 by volume and then top dressing with a layer of diatomaceous earth and then a sprinkling of sphagnum moss to mitigate moisture loss by evaporation at the soil surface. For shallow pots, I mix chunks of coconut husk with diatomaceous earth at a ratio of about 1:4 and then top dress with sphagnum moss. That's all for deciduous trees.

For conifers, I use straight perlite or pumice and then top dress it with diatomaceous earth and/or sphagnum moss.