How doi raise the Ph of my soil

I purchased a BlueLab soil ph open. It is correctly calibrated. I used it to check the ph in several of my trees in development. It’s reading a soil ph of 4.8-5.5 in several trees. That’s seems way too low
What can I addd to the soil to raise the ph. I know how to adjust water ph but soil ph is news new frontier for me.

Thanks for the help I raise appreciate it

Lime (Calcium Carbonate or a mix with Magnesium Carbonate) is the standard addition to raise the pH. it is sometimes referred to as a soil sweetener since acid soil is considered to be sour. Bone ash (Calcium oxide + Phosphorous oxides – often hydrated) should also be possible. Be careful to not use too much and retest after a few weeks before adding more.


Thank you for always taking the time to help other with the information. I really appreciate it

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Marty, do you know if watering with a higher pH would raise the soil pH over time? Instead of having to add amendments to the actual growing medium?

I have a soil pen coming soon, so I’m not sure yet testing it out for myself.



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I have found that the pH of the water is probably more important than the pH of the soil since the water flows through the soil with every watering. My water pH is about 8.6 and I inject some acid to reduce the water pH to 6.5-7.0. My trees do better when I use the lower pH water, but after a couple of Asymmetry podcasts I am not as concerned about getting it below 7.0. In summary, I feel the pH of the water is more critical than the pH of the base soil for our bonsai unless you are trying to grow in something that is either very basic (oyster shells) or very acidic (straight peat moss?).


What is the soil you are using on THESE trees? Kanuma, or maybe high sphagnum content?
What is your water pH? (You need to rinse your probe in distilled water between readings…) Whats the pH in distilled water?
Are you pulling several tablespoons of soil, shaking in a volume of distillled water, settling for 1 hour, then measuring? Sticking the probe into the soil gives a spurious reading…
I found a great way to get a reliable reading is to run a cup of water through the bonsai pot, collect in a CLEAN tray, and measure this. It gives pH for everything going on in the pot… Organic feritilzer lowers this pH. On my healthy trees, it comes out at about 6.7. My water is about 7.8. Still working my head around this…


@Bcreehan is the BlueLab soil ph pen producing credible measures of the soil pH also with substrates like pumice, akadama and lava rock, of different granulometry? I know BlueLab and they are very good, I have their device for solutions and it is great, but I also know that the bonsai mix of soils and granulometry can be problematic to measure ph and EC. I would love to know your experience. Thanks.

Because these trees are in early development they are in a 60/40 mix of perlite and Fox Farm Happy Frog soil. It seems to be working alright. The lower ph trees are the 20 or so that I potted last year in spring and the trees I potted this spring read around 6.2-6.8 I’m taking the reading a few hours after watering so the soil is damp and has had time to interact with the water. My main concern is how low it seems to be.

6.2-6.8 is not low, I would say that it is quite perfect as the plants strive in the range 6.0-7.2 where their ability to absorb the mineral nutrients is maxed. Why are you concerned?

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The 6.2-6.8 trees are great. I’m not concern with those.
It’s the group of trees I plant last year that are showing 4.2-4.8. I mentioned the healthy trees to show the difference in ph from one year to the next.

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