Kanuma pH acid or alkaline?

there seems to be a controversy regarding the pH of kanuma. I stated in another thread, that kanuma is more acidic than akadama, which is information I read about the 2 soils.I received a private message from an IBC member stating the contrary. This person alas will not accept private messages, so I am asking for more information. I have done a lot of searching at various websites, American and German and read in 2 books: Robert Z. Callaham: Satsuki Azaleas and Alexander Kennedy: Satsuki. Both stated that kanuma is acidic. Several sources for kanuma state in their websites, that kanuma is acidic. Any information, discussion on this topic is most welcome. If there is misinformation in print and on the web, it needs to be changed.thank you!kora

Journal of American Bonsai Society Vol 43 #4 2009 page 6 had a chart of various soil components. It listed kanuma as pH 6.4 and akadama pH 6.5-6.9

It also listed kanuma having a cation exchange capacity (CEC) of kanuma=62 and akadama=31.

Frank

I never measured it but kanuma soil should be acidic with a pH in between 4.5 and 5.5.

Only solutions have pH so rock/gravel/substrate itself has no pH. When put in water kanuma soil will lower the pH. But the degree to which the water is lowered is not the same as the soil pH of a 100% kanuma soil. I guess the issue here is the ratio between actual kanuma pumice and water.

This is why I suspect people come up with different measurements. But soil pH is not a straightforward thing.

Hi,

it is definitely acid as 7.0 is neutral, anything higher is alkaline.

I powdered up some oven dried kanuma, did a soil ph test with the liquid and powder it came with and got 5.5.

The same test with akadama gave 6.5 - all these soils will probably vary a bit depending on thearea they are dug from, but all are acid to some degree.

repeated watering with alkaline or neutral water will change the pot ph from acid though.

cheers Marcus

This is the list that Frank referred to, from a post on Bonsai Study Group (moderators, if this is not OK to post, please delete). Frank, was that you who posted it over there? What does the "n" refer to under turface pH? Did the article describe the methods used to make the measurements?

Soil Component CEC pH water retention

---

Kiryu River sand 11.7 5 low
coarse sand 0 7 low
Perlite 1.5-3.5 6.5-7.9 low
akadama 31.4 6.5-6.9 high
red lava rock 10-30? 6 med
haydite/calcinated clay 15-40 7 med
decomposed granite 1-15 6.5-7 med
pumice 15 7-7.5 low
Kanuma 62 6.4 high
Turface 33 n med
pine bark 53-100 4-5.1 high
charcoal >200 6.7-9.7 low
sphagnum peat 100-180 3.9-4.9 high

Glaucus wrote:
Only solutions have pH so rock/gravel/substrate itself has no pH.

-Jay

Chris

The 'n' might simply mean neutral, yet my experience turface, tested in distilled water, brings a pH of around 6.5. I believe that is also mentioned on their website somewhere in the specs.

I'm thinking of splurging next year for some kanuma to put my American beech in as he still seems unhappy in turface even WITH nothing but rain water.

-Jay

coh wrote:This is the list that Frank referred to, from a post on Bonsai Study Group (moderators, if this is not OK to post, please delete). Frank, was that you who posted it over there? What does the "n" refer to under turface pH? Did the article describe the methods used to make the measurements?

Yeah I posted that. The article did not specify the methodology; there was no explaination for the 'n'. I assume it means neutral 7.0.

Several years ago, I had several soil samples analyzed professionally at the Clemson (University) Extension Agency. I would tend to place more validity in such analyses than in tests we may do at home without the availability of carefully calibrated equipment. The results were interesting, and a bit surprising. Two mixes having the components listed, as well as samples of akadama and kanuma were analyzed.
Sample One: 1/3 Turface, 1/3 Pine bark mulch, 1/3 well driller’s gravel
< Soil pH 5.8, CEC 12.4 meq/100g
Sample two: 1/4 Turface, 1/4 Pine bark mulch, 1/4 well driller’s gravel, 1/4 mushroom compost
< Soil pH 6.4, CEC 42.2 meq/100g
My sample of Akadama yielded a pH of 5.5 with a CEC of 8.9 meq/100g, and the sample of kanuma had a pH of 6.2 with a CEC of 7.5 meq/100g. As you can see, the kanuma sample was moderately acidic with a pH of 6.2, but the akadama's pH of 5.5 was more acidic, in this test. I even called the agency to confirm the samples were not mixed up. They also reported levels of K,Ca,Mg,Zn,Mn,Cu,B,Na.