Biochar in pots and pH

[PlantRoom]

Does anyone know what the ratio of biochar to soil mix should be in indoor pots so that the soil pH doesn't rise too much? I am inoculating some homemade biochar20%/worm castings20%/growstone57%/malted barley3% mix at the moment, I didn't wash the small amount of ash from it as I want the benefit from the Ca, now the char is sat in a bacteria, organic nutrient and worm casting mixture which is reading around pH9.5. I'm going to use a soil/coir mix so assuming that the pH of that will be in the range 5.5-6.0. Also I'm not sure whether to drain off the liquid before adding the solids to the soil/coir mix.

I've read around a bit and figures range from 5-25% biochar but I can't find anything that might give a clue as to what the final pH might turn out to be? Anyone know how to calculate it?

 

[PlantRoom]

So I think I've just answered part of my own question, KIS is recommending 5-8% char. On that basis I can calculate how much slurry to use (think I will drain excess liquid before using). But I still don't know how to calculate the final pH.

 

[Eyes on Fire]

Sweet lime will help stabilize it too.

 

[Arthur]

If you want to be accurate, you need to mix, and then slurry test and then adjus till you hit the numbers your looking for. % will be difficult to give as the soil mix you use may /will have different ph properties than what's sitting in my grow area.

I use a 1 to 1 on the slurry 1 part soil and 1 part water that will be used for grow. Mix wait 5 minutes and test ph.

 

[PlantRoom]

Thanks for the advice fellas (assuming you are fellas )

pH tested 2 days in and it's dropped to 8.5, is pH dropping a function of the bacteria activating? Will check periodically until ready to mix it with soil.

 

[PlantRoom]

Update on the Biochar slurry, it has dropped to pH7.5 today, I'm guessing that the bacteria is doing this as it feeds on the Oxygen, insect frass and worm castings, I've not read of this phenomena anywhere yet although I'm assuming this is how soils are able to self regulate pH levels, bacteria doing most of the work, at least the pH is moving in the right direction

 

[Eyes on Fire]

this is exactly right mostly.However when you start adding different top coatings and AACTs will change and swing the PH n stuff. the micro life does lots of the work.But the sweet lime helps it bounce back faster.

 

[PlantRoom]

this is exactly right mostly.However when you start adding different top coatings and AACTs will change and swing the PH n stuff. the micro life does lots of the work.But the sweet lime helps it bounce back faster.

Just had a search for sweet lime on the UK side of the pond, can't find it for sale, must just be available state side?

EDIT: Sweet lime = Dolomite lime, sweet

 

[Eyes on Fire]

Garden Lime from Jobes or similar product ,Dolomite Lime powder,Prilled Lime even. which is essentially garden pellet lime.should be siomewhat easy to get there.Jobes,Epsoma Garden Lime will work.I typically use two or three type of lime depending what Im doing with the soils n plant type.But garden Lime or a combo of the Dolomite Powder and garden lime is gonna be the best,but either will be fine.

 

[PlantRoom]

Another update, pH has dropped to 6.8 and the slurry has thickened slightly, bacteria going into superglue phase?

Now I have the opposite worry that it might become too acidic, have to start shopping for some lime