Using Humic Acid in the Compost Pile

by Haydn Gunningham
(Perth - Western Australia)

It appears that the humic acids available in Australia are of poor quality as the process of extraction from Leonardite (ie brown coal) tends to de-nature the biology of the humates. Therefore, instead of using the humic acid as a food source for brewing compost “tea”, it has been suggested that I use it to moisten my compost pile. I am using a 26% liquid concentrate and dilute this concentrate in water by 100:1.

Question 1: Would you please advise if I should (or can) use a stronger mix say, 20:1 and if so would this benefit the compost?

Question 2: Would you pls ask your "Tribe" members if they know of a good quality source of humic acid is available in Australia?

Thank you.

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Mar 01, 2012
Humic Acids and Your Compost
by: Dave

Hi Haydn,

I'm glad someone advised you against using humic acids in your compost tea brewing. I know it was for different reasons than those I'm about to state, but you may have saved yourself some bacteria. Are you wondering what the heck I'm talking about? Let me explain...

A couple weeks ago, I was speaking with Tim from Microbe Organics (our go-to guru for compost tea microscopy and analysis) and he suggested that I stop recommending that humic acids be added to compost tea. He and several others in the industry have noticed that the addition of humic acids to teas delays the growth of bacteria. Interesting, eh?

My microscope will be arriving in the mail this week, so once I'm well versed in it, I too will hopefully be able to verify this for our members. I will also be updating this information on our various compost tea making pages within the next week or so.

As for your specific questions regarding appropriate mixing and dilution rates, I am not your best source for this information. However, I do have an incredible source for humic and fulvic acids in Australia, and I would bet the farm that they'll be more than able to answer your specific dilution rate questions.

Please visit - Nutri-Tech Solutions*

Once you've gotten a response from them, please post their reply and advice in this comment section so we can all learn with you.

That all being said, I do have a feeling your best bet in terms of figuring out the answers to your questions is to run a few of your own experiments. Create several different piles of compost ingredients. Mix up various concentrations of humic acids, apply in a controlled manner, and then send your finished compost off to a lab for nutrient analysis. Just be sure to document everything really well, have a control pile, and turn each pile with the same frequency and vigor. I don't want to create experimenter bias, but I do think less is more when it comes to your liquid humate products.

Your Soil and Health Scout,

*Please note that I have no affiliation with NTS. I have simply been following their work and they appear to be a highly ethical and knowledgeable company.

Mar 04, 2012
Using Humic Acid in the Compost Pile
by: Haydn

Hi Dave,

An excellent reply, thank you. I guess you are right, I would need to build test piles to prove it. Maybe I will finish off this 20 lt drum in the compost piles slowly and probably not replace it.

The comment by Tim on the delay of growth of bacteria is interesting when brewing and I’m keen to hear how you go with your microscopic testing of brews with and without humic acid. I guess the other variable is the source of the humic acid. I think you guys in Canada /America can get hold of a better quality product than our local Australian ones.

Quite a coincidence re you mentioning NTS: It was only last week I contacted them (as a result of viewing your superb web site) and spoke with an agronomist re a plant growing problem. The cost for the helpful agronomists advice?...NOTHING! Amazing eh?

Happy composting

Mar 04, 2012
Humic Acids and Compost
by: Dave

Thanks for all this feedback Haydn.

I will keep you posted on the humic acid/bacteria info. It's going to take a little time to get used to my new microscope, but in due time, I'll master that baby!

That's great news re NTS. I had a hunch that you would find great service with them.

Please keep in touch.


PS - Guys, it's really helpful when you provide feedback/follow-up (like Haydn has done) to the responses you get from your initial questions. It's the only way we're going to learn this material together...via supporting one each other.

Apr 21, 2015
did your research confirm this?
by: Anonymous

thanks for the great info. Did your experiments with microscopy confirm that humic acid delays bacterial growth?

Apr 22, 2015
Using Humic Acid in the Compost Pile.
by: Haydn

G'day Mate,

I never did take testing to the level previously discussed. It appears there are many types of humic acid sources but it seems they fall into two main catagories; naturally occurring and those extracted from leonardite or brown coal using strong acids.

Everything I've read about composting suggests that even humics produced chemically, are rectified in the pile.

I often add chemically produced humic acids (26%) in the compost pile and know via growing tests and comparisons with other composts that the quality of the compost with humic acid is very high.

Nutri-Tech Solutions in Queensland Australia is doing some excellent research into the use of humic acids in commercial growing and is currently investigating their use in clay soils. They will be able to offer much better advice than I can.

Hope this helps.

My question, if you don't mind, do you have any idea where Dave the Compost Junkie went to?


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