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Soil and Composting: Humic Acid

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Forum: Soil and CompostingReplies: 5, Views: 62
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Cantonment, FL
(Zone 9a)

March 30, 2011
12:54 PM

Post #8460764

I told my local gardening supply center that I have a huge pile of oak leaves to compost and she suggested a product with humic acid and ash. The label said it's for general soil improvement and composting but what I read indicates that it adds carbon for microbial growth. I've already got carbon- don't I need nitrogen?


Anne Arundel,, MD
(Zone 7b)

April 1, 2011
9:45 AM

Post #8464924

You are right, Yes you need nitrogen and moisture in the leaves so the micros can eat the leaves.

I just read a little. Humic acid is really good in the soil but as part of the soil chemistry, which we hopefully get thru composting etc. Shame on the producer for saying that it is good for composting implying to me " it will speed up decay of high carbon pile".

Would you believe that there is an International Humic Substances Society?
Cantonment, FL
(Zone 9a)

April 1, 2011
1:49 PM

Post #8465351

Those people need to get a life.


Anne Arundel,, MD
(Zone 7b)

April 1, 2011
6:48 PM

Post #8465942

well, their life is dirt and they're probably proud of it.
Humic substances put the 'black' in Blackwater River !
This next is probably more than you care to know but info that may be helpful to somone who comes along actually looking for more about humus.
Here's a quote from the IHSS page titled "What are Humic Substances?"

"Humic substances (HS) are major components of the natural organic matter (NOM) in soil and water as well as in geological organic deposits such as lake sediments, peats, brown coals and shales. They make up much of the characteristic brown color of decaying plant debris and contribute to the brown or black color in surface soils. They are major components of NOM in surface waters and at higher concentrations can impart a dark color, especially in brown fresh water ponds, lakes, and streams. In leaf litter or composts, the color may be yellowish-brown to black, depending on the degree of decay and concentration.

Humic substances are very important components of soil that affect physical and chemical properties and improve soil fertility. In aqueous systems, like rivers, about 50% of the dissolved organic materials are HS that affect pH and alkalinity. In terrestrial and aquatic systems HS affect the chemistry, cycling and bioavailability of chemical elements, as well as transport and degradation of xenobiotic and natural organic chemicals. They affect biological productivity in aquatic ecosystems, as well as the formation of disinfection by-products during water treatment. "

It goes on for a few more paragraphs but gets progressivley more technical? chemical.
Provo, UT
(Zone 5a)

April 2, 2011
3:20 PM

Post #8467337

sallyg.. thanks for that link.. i for one can never learn to much about gardening..soils..related topics..
i do alot of composting,sheet composting,leaf collecting(for composting) and vermiculture..
it makes a benificial difference in my gardens..and the plants i grow..
thanks again for the link and asking on this topic...


Everett, WA
(Zone 8a)

April 4, 2011
8:02 PM

Post #8472641

I always thought that "humic acids" were what composting produced. Not what you need to stimulate decomposition.

I think you are right: oak leaves need nitrogen. If it were me, I would also try to chop them up a bit and age them ... don't oak leaves have a lot of tannin? I would expect that to slow a pile down. A friend of mine always aged last year's oak leaves in bags, while composting this year's leaves.

Ashes might raise the pH, counteracting the oak leaves' acidity, which that SOUNDS good, but I've also read that liming a compost heap encourages nitrogen to escape as ammonia (I don't really know, YMMV).

When anything organic oxidises (incompletely) , some of the breakdown products are likely to be -COOH, the carboxyl group. With just one more carbon, it's acetic acid (vinegar).

Break it down a little more, and it's carbonic acid (H2CO3), or carbion dioxide and water.

I guess the name "humic acid" comes from "humus with carboxyl groups", or "oxidising humus".
They are supposed to be able to encourage rocks and mineral soil to break down and release nutirients like phosphate, sulfate, potasium etc.

I first heard the name "humic acids" in 1940's gardening books, and thought it was so vague it was pre-scientific home gardener's mumbo-jumbo. But it turned out to be a "real name" and from what you say, is still in use.

But I would take any future advice from this garden supply clerk with a grain of salt or humor.


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