Kanuma as a soil amendment

[loneroc1]

Howdy all,
My well water is fairly high in pH and dissolved solids.  It's a constant effort to maintain an acid soil condition, especially for my potted citrus.  I recently got ahold of some kanuma "soil". It has a tan perlite-like appearance and feel and it's very acidic in reaction.  It's a volcanic stone used by bonsai enthusiasts and is imported from Japan.  It's often used straight for bonsai azaleas and other acidophiles.

Has anyone tried this as a soil amendment for potted citrus?  I thought I'd give it a try and see if it helps maintain an acid condition in citrus potting "soil".   Thanks!  Steve H.

[Millet]

Loneroc1, f from the description  of your water, your water seems to be close to my well water.  My water is high in bicarbonates, which after repeated watering of my trees, was causing a growth problem.  Therefore, I switched to using rain water collected off of three large barns.  Kanuma's PH of 4.5 to 5 is somewhat low for citrus.  I also noticed the soil holds more water in weight then the soil itself  This not a problem as long as the medium continually also supplies oxygen to the root system.  It is not the water that damages citrus roots, it is the lack of oxygen.   If you go ahead with your Kanuma experiment, PLEASE keep us up from time to time with the results of your tree's growth and health.  Thanks for your post.

[loneroc1]

Yeah, my water is crap.  A few years back I put in a deeper well.  I swapped my 15 foot deep sand point, which essentially provided soft rainwater, for a much deeper well laden with minerals. Before I realized what was happening I lost hundreds of plants.
Some of the bonsai sites recommend the use of kanuma as an additive to decrease pH of the medium.  For true acidophiles, such as rhododendron, straight kanuma is the medium of choice. As you might expect, there are nearly as many online opinions as posters.  One of the things I like about the TF forum is the stock most members place on actual scientific data.  It's a refreshing viewpoint now that we live in a post-truth world.   We'll see how it goes.--- Steve H

[pagnr]

I looked at a Japanese mine website
http://www.tachikawa-heiwa.com/Introduction.html
The Kanuma is an Aluminium Silicate, 40% Silica 25% Aluminum so is the Akadama Pumice. 58% Si 17% Al.
Another Aluminum Silicate is Zeolite, which has a high Cation exchange capacity, ie it can remove elements.
Zeolites have a porous structure that can accommodate a wide variety of cations, such as Na+, K+, Ca2+, Mg2+
They are used in water treatment plants to soften water.
Maybe the Kanuma can also act in this fashion ? The CEC Cation exchange capacity may or may not be as high as Zeolites.

Have you thought of using pool chemicals such as HCl to drop the pH of the hard water, or greenhouse treatment systems ?
https://aggie-horticulture.tamu.edu/ornamental/greenhouse-management/treating-irrigation-water/

Also the types of fertilizer you use might have an impact. CaCo3 Lime will push pH higher than CaSo4 gypsum if used as a Calcium supply.
Many fertilizers also have Mg Zn Fe Mn etc as So4 forms, which might be helpful.

If you test your water, you can check which elements are abundant, ie Ca and Mg, and use fertilizers that are lower in those so you are not adding to the pH problem.

 

[Millet]

pagnr excellent post.  Full of information.