Humic acid and pumice?

[One First Matter All]

Hi all,

I have a question about the interaction between humic acid, pumice, and fertilizer. I have read through Bonsainut's previous posts on humic acid, and I can't seem to find the answer I seek.

As I understand it, humic acid increases the CEC (cationic exchange) of fertilizers, and this increase is especially important when using inorganic bonsai substrates. The idea is that, without either organic material in the substrate itself or else an additive like humic acid, most of the fertilizer will simply pass right through the inorganic substrate and onto the ground, with the plant receiving little in the way of its nutrients.

My question concerns the interaction between humic acid and inorganic materials like pumice. I get how humic acid binds to the fertilizer, but I don't understand how this binding solves the problem of fertilizer simply passing through the substrate--unless, that is, humic acid is especially good at binding to the substrate. Does that make sense? In other words, I want the fertilizer to "hang around" a little longer in the substrate, and it seems that, by binding to the humic acid, we have accomplished that goal, but only if the humic acid is itself "bound" to the substrate. Does humic acid "stick" to the pumice, thereby allowing the fertilizer that "sticks" to the humic acid to hang around a little longer?

I don't know enough about chemistry to answer this question, so I hope someone out there does/can.

 

[Wires_Guy_wires]

Humic acid is larger in size, and thus takes more time to pass through the pores in pumice.
Eventually it can and will seep out, just like your fertilizer. With the pore size of regular pumice, and the physical molecular size of humic acid, I think the difference isn't that large.

I've done pore-related separations of proteins with a size difference of around 3000% and it takes just a couple millilitres of difference to wash the smallest out, and the largest. These proteins were way bigger (in all 3 dimensions) than humic acid molecules, and the pores were smaller than the ones found in pumice.

I'm not sure as to how humic acid would adhere to pumice other than travelling through the pores and eventually washing out.

 

[One First Matter All]

Eventually it can and will seep out, just like your fertilizer.

Thanks for your reply. So, is there any point to using humic acid in an inorganic substrate like pumice? Does its temporary stay in the pumice increase the fertilizer uptake by the plant?

 

[BrianBay9]

Humic acid is larger in size, and thus takes more time to pass through the pores in pumice.
Eventually it can and will seep out, just like your fertilizer. With the pore size of regular pumice, and the physical molecular size of humic acid, I think the difference isn't that large.

I've done pore-related separations of proteins with a size difference of around 3000% and it takes just a couple millilitres of difference to wash the smallest out, and the largest. These proteins were way bigger (in all 3 dimensions) than humic acid molecules, and the pores were smaller than the ones found in pumice.

I'm not sure as to how humic acid would adhere to pumice other than travelling through the pores and eventually washing out.

This is a good point that I hadn't considered. We are essentially setting up a low resolution column chromatography system with pumice in pots. But I agree, there's not enough difference in molecular weight to retain humic acid for all that much longer than other fertilizer components. A while back I tested the retention time of primary amines from ferts in 15 cm deep pumice, fertilized heavily once, then watered every day. Took about a week before I couldn't detect leaching amines from the bottom. This is why I fertilize once a week with my inorganic soils. I bet humic acid is not much different.

 

[WNC Bonsai]

That is why I use pine bark as the organic substrate. It binds both nutrients due to its relatively high CEC and it also will bind humic acid, plus it holds moisture and serves as a good substrate for beneficial bacteria. You could also add some biochar or activated charcoal.

 

[Wires_Guy_wires]

Thanks for your reply. So, is there any point to using humic acid in an inorganic substrate like pumice? Does its temporary stay in the pumice increase the fertilizer uptake by the plant?

There is a point, namely that it helps plants in other ways and provides a carbon source for microbes.
The temporary stay can lower the amount of runoff nutrients a small percentage.

But one can wonder what difference a few percents make. Humic and fulvic acids are more expensive than nutrients, and as a carbon source there are better materials.
I still use it, but that's because I have it lying around. The benefits are more to the plants themselves than to nutrient availability I think. Humic acid does interact with plants in some variable way or form and they do seem to like the use of it. But a good feeding regiment would benefit the plants as much I think.

 

[luvinthemountains]

Took about a week before I couldn't detect leaching amines from the bottom

Do you have any information on what the curve looked like over that week? I would be curious to compare ppms with weekly fertilization versus "slow release" polymer fertilizers. My assumption would be that you get decreasing convex curve between weekly fertilizations (frequency of one week) and a left-skewed standard curve with slow release (frequency of 3-6 months?), but the average available nutrients to the roots over time might be higher with a weekly fertilization routine.

 

[cmeg1]

Very good stuff the humic and fulvic acids…I use with everywatering.The humic just binds to everything after several waterings and is a chelator.Essentially a claw that holds mineral ions at roots so as not to wash away.The media will change its color in a few waterings and can see then.Also a great ph buffer the Humic type in RO or DI water.
The humic and fulvic and kelp bio’s essentially have all micro elements a plant needs and calcium too.
Quite simple really after some knowledge is attained.
Fulvic is much smaller weight and is good for nutrient absorption into roots and leaves( in as little as 4 hrs!!!)
I use so much fulvic in my nutrient I can get by with 20% less salts or ec!!! More water!!!
Humic does have a fraction of both humic and fulvic together.
Check the article from my hydroponic teacher!!!!
He is the hydro master for sure!
Also check the 5:2 ratio of humic:kelp.
Also check amino acids L glycine and L glutamate for 1000 X more calcium uptake.
I find powders much more effective in both cost and dosing properly.

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[BrianBay9]

Do you have any information on what the curve looked like over that week? I would be curious to compare ppms with weekly fertilization versus "slow release" polymer fertilizers. My assumption would be that you get decreasing convex curve between weekly fertilizations (frequency of one week) and a left-skewed standard curve with slow release (frequency of 3-6 months?), but the average available nutrients to the roots over time might be higher with a weekly fertilization routine.

Sorry, I wasn't that sophisticated in the experimental plan

 

[luvinthemountains]

Sorry, I wasn't that sophisticated in the experimental plan

Lol, you were more sophisticated that I have been...that is, sitting around and just wondering stuff. Thank you for sharing!

 

[One First Matter All]

Very good stuffThe humic just binds to everything after several waterings and is a chelator.

Goodbye from Maximum Yield

In print and online, Maximum Yield is your source for cannabis and cultivation knowledge, with informative grow articles and tips to enhance your life with mmj.

www.maximumyield.com

Thanks for the post. What do you mean when you say that humic acid binds to everything? I don't follow you there. I understand that its dark color may stain the pumice after a few waterings, but staining pumice is not the same as forming a chemical bond with the pumice that then allows for better fertilizer uptake by the plant, right? Or am I misunderstanding?

 

[cmeg1]

Thanks for the post. What do you mean when you say that humic acid binds to everything? I don't follow you there. I understand that its dark color may stain the pumice after a few waterings, but staining pumice is not the same as forming a chemical bond with the pumice that then allows for better fertilizer uptake by the plant, right? Or am I misunderstanding?

Always just followed instructions and plants look great.I figure if roots and everything are dark colored there is humic acid there and it is chelating the ions and keeping them available.
Good ph,good water and everything should be ok as far as I can see…….it excells in hydroponics media such as pumice.
All I can say is I grew some very nice high brix plants using the stuff……lots of experimentaion.I mainly use fulvic acid now for its absorbing abilites of ions into plant tissues to lower my overall salts EC because of the fantastic nutrient uptake.
It is fantastic conbined with kelp……I get back budding on 1” shoots.

 

[WNC Bonsai]

Looking real good. I just received an order of Gro Power 12-8-8 fertilizer tablets recommended by Bjorn that contain 4% humic acid. We’ll see how that works.