Volcanic dust as fertiliser

[BonsaiPancake]

I recently bought some volcanic dust for my trees and I'm curious about more of the scientific side of things.

This is the marketing info (can't find anything else about this exact brand):

Screenshot 2022-04-23 140925.jpg

It's extremely fine which makes me think a lot of it will wash through the pot quite quickly so larger doses might be needed.

I've read conflicting information about how it works. The logic that seems to make the most sense is that some of the minerals are immediately available to the roots (akin to a liquid fertiliser), and as it breaks down, some other minerals then become available.

I've recently done a lot of research into the science of fertilisers (the book 'Modern Bonsai Practice' was awesome for this), so I'm really curious how this fares compared with traditional fast and slow fertilisers.

Does anyone have any information, readings, or general anecdotes on using volcanic dust for bonsai?

[shibui]

Note there is no mention of this being a fertilizer. Fertilizer must have a measurable quantity of N,P or K.
This product supplies some trace elements which are listed.
Trace elements are also important for plants health but are required in very small amounts. Some are water soluble and may leach out of the pot, others are not water soluble and are dissolved by plant or soil acids before plants can use them.
Trace elements are usually present in soils but some soils are lacking in one or more so adding extra trace elements makes sense.
Ph can affect which trace elements are available to plants and which are 'locked up' To counter that we can either add more or unlock the ones present by changing soil pH. Note the use of spoils here meaning ground, garden or farm soils.
In potting soil things are very different. Modern potting mixes have no soil so very few trace elements. Because of this, modern 'balanced' fertilizers have trace elements added in correct proportions so they are present every time you fertilize.
Some organic fertilizers do not contain all the necessary trace elements so extra may be required depending on the type of fert you choose to use.

There are a great many fringe plant health products. Some have uses, others seem to be more about marketing in the hope of convincing growers to part with money.

[BonsaiPancake]

Good point on it not being technically a fertiliser!

While I do try and avoid the snake oils, there really isn't much negative info on it which is why I'm so curious about it. Lots of generally positive comments.

On paper it looks super useful in terms of the trace elements, and it's actually quite cheap given the recommended dosage.

Would love to see some in depth studies on it, but for now I might experiment with a few trees and see how they go.

Appreciate the detailed response!

[dansai]

A very interesting Mirai Podcast on soil science and minerals if you want to have a listen.

On the dust, the idea of using this sort of product has been around form ages. I remember doing my first veggie garden over 20 years ago and being recommended "rock dust". It may be useful as an additive to organic fertiliser cakes as described here.

If you do listen to the podcast above, the guest, James, talks about minerals getting out of whack, and that adding more of everything can make the issue worse. Although he is talking more in terms of agriculture and there is much discussion about its use in a Bonsai container as it is a very extreme environment. I believe James may have been working with Ryan since the podcast on research and testing of the Bonsai at Mirai.

My growing on mix I use in plastic nursery pots is made locally and has about 2% basalt fines. These range from dust to about 5mm. Basalt is a volcanic rock that has a range of minerals and the idea is that they are released slowly by both watering and root action. I am going to get a bag and sift out the really fine stuff and use it as an additive for my Bonsai mix.

[treeman]

Basically a waste of time. The silica will not be in an available form (basically silica sand) so there's 50% gone.
The K can be useful. The Fe will not be available. The Mg might be available? For the rest, there is so little, 1/4 teaspoon of trace element mix will probably supply 10 times the amount. The ''organic carbon'' will be 1 millionth of what is already in your potting mix if you use bark.
As for the ''much more'' I am highly dubious.
The only instance I have heard of rock dust being useful is as reactive rock phosphate and potassium from granite dust. Both of which are already abundant in ordinary fertilizer.

[treeman]

Modern potting mixes have no soil so very few trace elements. Because of this, modern 'balanced' fertilizers have trace elements added in correct proportions so they are present every time you fertilize.

Yes, and if you buy a mix which adheres to the Australian Standard, it will contain enough TE for at least 3 and probably 6 months of good growth without adding more. Usually with such a mix, it is difficult to notice the difference in plants fertilized with NPK + Ca Mg and TE or just with NPK or even just N for the first few months. Ca, S and possibly B are the first to run out. There is enough Fe held to last years without adding more!

[shibui]

Yes, and if you buy a mix which adheres to the Australian Standard, it will contain enough TE for at least 3 and probably 6 months of good growth without adding more.

I note the caveat of 'adheres to Australian standards'.
I'm all in favour of using commercial potting mixes and get mine made up so I don't have to worry about all the additives.
Unfortunately it seems to be a trend now to DIY potting mix so we have a great many people with little knowledge mixing various components and expecting the results to be better than the original.
There's a great deal of science and experience that goes into producing potting mixes, including suitable fert and trace elements but there's little talk about including any of that in DIY mixes.
Thanks for pointing that out. Others should take note.