Measuring pH in Diatomite and other granular potting mix

[Ash]

Hi,

Does anyone recommend a technique or product for measuring pH in very granular growing media like diatomite?

I am examining some leaves for nutrient deficiency and suspect a minor iron deficiency in a particular tree- possibly induced by high pH in growing media (diatomite+charcoal) or possibly induced by the regular use of a high potassium fertilizer. The problem I have is that my kits for testing pH are really for fine 'tilthy' or 'silty' soils. In the case of the diatomite I am really only measuring the pH of the water I just added using a testing kit. The diatomite is the Maidenwell variety.

I am unable to use my usual foliar applications of micro-nutrients like iron chelates at the moment because the bright light and hot weather is causing leaf scorch where any salts form on the leaves post spraying.

any ideas or suggestions appreciated
thankyou

Ashley

[Jow]

You could try to crush it to dust... It breaks down with some encouragement.

[kcpoole]

Be interesting to try measuring PH of diatomite after being aged.
Let us know what you can find out

Ken

[Ash]

You could try to crush it to dust... It breaks down with some encouragement.

Yes Jow that is probably what I am going to do- thanks for the advice.

Let us know what you can find out

Will try Ken.

Has anyone else tested the pH of their diatomite mix for me to have something to compare with?

I notice there are discussions on here about high pH and neutral sources of diatomite. Can anyone give me any info on this? Is the Maidenwell source the one being used mostly for bonsai?

Overall the plants are growing lots and lots and lots of roots since I shifted to using it as my aggregate. I have used it for cuttings and they strike quite well provided it is not too fine, but all of them soon show young leaf interveinal chlorosis

cheers
Ash

[Bretts]

I find 100% of certain substrates will increase the chance of pH issues. I have seen my kanuma which is slightly acidic turn alkaline from the use of Dynamic lifter.
But I have two surprise pH issues with a mix I used on some Pines. They are not 100% high pH diatomite but what I thought was a decent mix that should buffer the high pH diatomite.
I have heard that some substrates are so nutrient "hungary" that when you finally got enough fertiliser into the soil these levels where harmful to the plant.

Not sure but my best guess is this has happened with a radiata that was constantly nutrient deficient. I have added heaps of fert on a regular basis but recently it went very yellow almost dead yellow
It seems a soil pH issue which would be helped with more regular foliar feeds. Might be too late for the radiata but I think stepping up the foliar feeding of the JBP lesser affected is a better plan for the short term than just keep chucking fert on the soil.
I will get a pic of them Tomorrow if I get a chance.

Crushing it is a great idea

Maidenwell is the more neutral Diatomite by product info and Mt Sylvia is higher by info supplied. I think Grant found similar results when he tested? I can't say I have tested them myself so guess I should.
Two substrates I have not found an issue with is akadama and maidenwell diatomite at 100% but I have not used maidenwell that much to say it isn't unstable.

I have been buying up any old bags of spongolite at Burnings whenever I find them as they changed thier ingredient for Aquarium plant grit to the whiter diatomite. I do not know of another way to get spongolite once the last of the old bags is sold so if you like using it grab all you can now