Testing your chars pH

[Getting A Life]

How do you test a chars pH?

 

I have some char here but I do not know how to test it and do not want to add it to soil if it is of the very high pH variety.

 

I have a soil pH test kit of the type that uses barium sulfalte, and a liquid and a water pH test kit with drops.

 

Suggestions? :)

[Essay]

How do you test a chars pH?

 

I have some char here but I do not know how to test it and do not want to add it to soil if it is of the very high pH variety.

 

I have a soil pH test kit of the type that uses barium sulfalte, and a liquid and a water pH test kit with drops.

 

Suggestions? :)

A thorny problem. Are you trying to repair poor soil, or trying to improve fairly good soil?

 

What is your char made from? How was it made? What was the HTT (highest treatment temperature) and for how long? Was this made through pyrolysis, gasification, or normal charcoal production methods? How coarse or fine is it?

 

Answers to these questions will predict (somewhat) a low or high pH. This can be a starting point - whether it's likely to be acidic or basic. The soil you are adding it to also affects how char will express its pH.

 

Char may be mostly acidic or basic, but it will contain a mixture of acid and basic functional groups on the char or within the pores. That's part of its magic - how it promotes microbial diversity. I've been adding char (from gasification) to compost piles. That helps reduce the GHG emissioins from those piles by enhancing the metabolic efficiency of the collective microbial population (better, faster decomposition).

 

Composting also ages or matures the biochar so that any extremes of acidity or basicity will be "eaten" by the microbes (or oxidized/reduced by the ambient conditions).

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Adding biochar to soil is an irreversible process (though you could later add different biochars to rebalance an undesirable shift linked to a previous biochar amendment), so be careful. Adding biochar directly to soil should provide great benefits, but it is possible get those strong changes in a negative manner also - as adding acidic char to acid soil might cause.

 

Fortunately, the char does not exist in isolation, but is always hosting bacteria and/or fungi. These turn the biochar into a good buffer, regardless of the starting conditions, after enough time - a few years at most, and many successions of fungal or microbial populations - until a balance is reached.

 

Choosing plants to suit the soil might be easier than changing the soil to suit the plants, but ultimately it is a balancing act. I'd suggest looking at improving the soil as a long-term process (years) and that any biochar addition, whether immediately good or bad, will help that process along and help generate a better soil in the end.

I'd also suggest reading "Teaming with Microbes" for good advice on soil doctoring.

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I have crushed up some char in water and used litmus and nitrazine papers to test the water, but I always get neutral to just slightly acidic. I think the biochar is so hydrophobic to begin with (until it ages a bit or is incubated with some living or other chemical systems), it doesn't react enough with the water to show any likely pH effects.

 

I'm gonna try leaving the crushed charcoal in the water for a day, and then test it. I'll let you know.

 

You might try mixing a sample of soil with freshly ground biochar and incubating at room temperature (in water) for a day or two and then testing the water. See if it changes much from what a similar trial, but without the added biochar, would indicate. You should probably do a "no biochar" trial without any time lag for incubation also; to rule out (or in) biotic changes to acidity.

 

If you try something like that, let us know how it turns out!

 

~ :hihi:

 

p.s. I have Lehmann's textbook on biochar; with lots of random examples of different chars and their associated pH's. If you can answer some of those questions in the first two "paragraphs" above, I can try and find a parallel in the textbook.

~ Good Luck!

[maikeru]

How do you test a chars pH?

 

I have some char here but I do not know how to test it and do not want to add it to soil if it is of the very high pH variety.

 

I have a soil pH test kit of the type that uses barium sulfalte, and a liquid and a water pH test kit with drops.

 

Suggestions?

 

Actually, I never check my char's pH... Plants seem to like its addition to the soil regardless. Keep in mind that the biochar's pH will change over time as the surface oxidizes and forms acidic and basic functional groups, things like carboxyls, phenols, carbonyls, etc., and reacts with organic matter, plant roots, and microbes. Changes may be noticeable in a few months.

 

pH will depend a lot on feedstock. Something like biochar made from poultry litter can have a pH of up to 9.9-10, whereas it appears that many wood biochars can be expected to be around 7-8. Green wastes around 6, perhaps because of an abundance of nitrogen, phenolics, etc. in the feedstock which will end up in the resulting biochar.

 

Production temp of char also moderates pH. It appears that chars produced around 400 C can be expected around a pH of 7-8, whereas higher temps encourage high pH chars of 11-11.5, perhaps because there's less N, O, and H (which would be in those functional groups) and a higher purity of carbon. Lehmann covers this in one of his books, and that's where I'm getting these values from.

 

Although the biochar might start off with a high pH, you may be able to modify it or let it age before addition to the soil if you're worried. I would soak or load it anyway before soil addition. And that may influence the pH further.

[Getting A Life]

The char is from tree privet. It burned fairly hot in an open fire a large log smouldered out leaving about 10 litres of char on it. I ground it down to about 10 mm pieces lots of it much smaller.

 

I can give it some nitrosol and seaweed for a soak and then mix it up with worm castings for a spell.

 

I hope to amend some potting mix with this.

[maikeru]

The char is from tree privet. It burned fairly hot in an open fire a large log smouldered out leaving about 10 litres of char on it. I ground it down to about 10 mm pieces lots of it much smaller.

 

I can give it some nitrosol and seaweed for a soak and then mix it up with worm castings for a spell.

 

I hope to amend some potting mix with this.

 

You will have a superb soil amendment at that rate, and I bet your plants will love it.

[Getting A Life]

OK. I got the char (about 2 litres) and put 20 ml liquid seaweed, 20 ml EM, 20 ml nitrosol with some water and made a slurry. After a few hours of this I added 2 litres worm castings and mixed it up. Then I got 8 litres 7 pH potting mix (compost, sand, clay) and mixed it all up making a soil that is damp enough for microbes to live in but not so damp it will be anaerobic.

 

I will leave this for a few weeks then pH it. If this char is ok it's my lucky day, there's literally tons of this wood available every year from pruning shelter belts.

 

How else can one test a chars potential for amending soil?

[Getting A Life]

And now it is 3 weeks later and results time.

 

The char, amendments and previously neutral soil mix is now pH 6.0

 

I am very happy with this result for Ligustrum lucidum char which is invasive here. :) These grow well over 30 feet and are a PITA weedy type plant sprouting everywhere. When I first moved in you literally could not walk around in the rear of the section as the saplings were impenetrable.

 

This soil will be spun out to 1 litre per 10 litre pot and have capsicums grown in them. 12 capsicums to be exact. 6 with sea solids, 6 without.

 

and then the next wait :confused:

 

Now I must make some drum type contraption so I can make more char, lots more of it. Source is no longer a problem, manufacture is.

[maikeru]

Take pics of the capsicums. Very interested in their progress and how they respond to the char. :)