Citric Acid

Does it have any benefit other than lowering pH? I know pH does not matter with organics but I still check to see what it is. When I bubble my alflafa/kelp/molasses tea my pH is at a perfect 6.4. When I add a teaspoon of citric acid to 5 gallons of tea it drops down in the 4s.

Plants love it but I would like to know if there is any benefit to it aside from lowering pH? Can it hurt the soil microbes?

citric acid makes chelates? am I off guys?

also I remember writing a thing about it being anti bacterial, but never read up on it after I posted it.... to busy



if your pH is perfect a you see it, why are you adding the citric acid, what have you heard that you would put in citric acid?

habeeb said:

citric acid makes chelates? am I off guys?

also I remember writing a thing about it being anti bacterial, but never read up on it after I posted it.... to busy



if your pH is perfect a you see it, why are you adding the citric acid, what have you heard that you would put in citric acid?

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I dont know why I add it. I have this lingering suspicion that it has some benefit.

By lowering the pH to 4ish, it will slowly raise back up to the 6.4 you had it at, making a wider range of nutrients available. You could let it sit for a bit to see how long it takes for the pH to stabilize. And if my memory serves, I'm pretty sure that citric acid is a root exudate already.

WALA = https://www.icmag.com/ic/showthread.php?t=191399&highlight=Citric+Acid

Another very useful additive is citric acid. The reason citric acid is a great additive is it bonds to P anions keeping them soluble in the rhizosphere and soil solution. Also citric acid helps the Krebs cycle. The reason P anions are not needed by plants at the same level of N, K or Ca is that P anions are not readily available to plants in nature, thus they have evolved to use lower levels of P than other major elements. I could explain all the why's but this post would get long and IME most people don't care about the why's as it gets technical in the topic of soil science.

In short, P anions are not very mobile in the soil solution (thin layer of water surrounding particles in media, soilless and soil) and are readily bound and made insoluble to media particles and other elements and organic substances; critic acid prevents this. The soil solution holds cations in equilibrium to the cations held in cation exchange sites of media particles. Roots exude large amounts of citric acid that keeps P anions soluble in rhizosphere and soil solution. Roots also 'feed themselves' by exuding critic acid (and other acidic chemicals/substances) that mineralizes P anions from organic matter like soft rock phosphate, etc.
Quote:
Originally Posted by spurr View Post
@ VG:

Here is some info about citric acid, and other ornic acids exudates by roots and microbes that solublize organic matter. For info on citric acid see the references below, esp. the first few, hope this is helpful. (thanks MM for the email)
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I hope I didn't come across as claiming their are saprotrophic plants; AFAIK there is no such thing, plants that where termed saprophytes** are really parasitic upon mycorrhizal fungi. Plants that were termed saprophytes are now termed "myco-heterotrophs" (see references below). I was referring to normal plants the can break down organic matter essentially feeding themselves, not myco-heterotrophs like non-photosynthetic orchards. Dicots tend to emit more organic acids than other monocots, esp. leugems, to my understanding.

** The term saprotrophic or saprophyte is now detritivores or saprophage. So saprophyte fungi are now called saprophage fungi.

I believe P is a major element that is freed (solubized via mineralization) from organic matter when roots emit or create weak acids in the rhizosphere and soil solution. Other elements like Ca, Fe, and I think N, etc, can be solublized too. The amount of ions the plant solublizes via acids isn't high, but can make a difference for P anion which has poor soil solution mobility and often gets tied up.

I'm sure you know most of this already, so please ignore any info that seems to assume you don't know something (like info about the soil solution).

Below I use "solublize" and "solublization" interchangeably with "mineralization"; to mean ions are freed from organic matter.


Here are some acids emitted or made by roots:

- Carboxylic acid: emitted by roots, lowers rhizosphere pH which effects ion availability (esp. P) and also solublizes some organic matter releasing ions the plant cant take up (ex. soft rock phosphate especially when the bulk soil pH is weakly acidic like 6 to < 7).

- Carbonic acid: similar to carboxylic acid but carboinic acid dissociates back into Co2 and water in the presence of water. Carbonic acid is formed when the roots emit Co2 and the Co2 mixes with water. Carbonic acids are pretty stable, however, in the presence of water it can dissociate into Co2 and water. Carbonic acid are similar to carboxylic acid in terms of rhizsphpere pH, and pH of soil solution and mineralization of some types of organic matter. Carbonic acid can be dissociated into Co2 and water via. exudates by bacteria (i.e. "carbonic anhydrase") that prefer neutral to basic pH levels.

- H+ protons: emitted by roots when roots take up ammonicial nitrogen such as ammonium (NH4+). This is why ammonium is said to be acidic, because of the reaction by the roots after taking in the cation. When H+ protons are emitted by roots it lowers rhizosphere pH and also can solublize some organic matter freeing ions the roots can use. When roots absorb nitrate N they emit bicarbontes, which are basic, and is why nitrate is said to be a basic (alkaline) form of nitrogen (roots also emit anions when nitrate is absorbed).

- Citrate (ex. citric acid): emitted by roots and lowers rhizosphere pH and can solubilize some organic matter. One of the acidic exudates with the highest level release by roots

- Oxalate: can provide nearly the same level of mineralization of soil P (from organic matter) as citrates. Oxalate is an acidic exudate of some mycorrhizal fungi (ex. AM fungi) used to solublize soil P.

The acids listed above is not a complete list, just an example. By the process of mineralization of organic matter the exudates (ex. citric acid) releases ions into rhizosphere and the soil solution (thin film of water surrounding media particles; where microbes and ions can be found). The roots can then use the ions in the soil solution or rhizosphere depending upon the pH of the liquid and solubility of the ions. The soil solution has an equilibrium of cations to those held by media cation exchange sites. Citrate has a large affect upon P anion in terms of increasing their bio-availability to roots, this is in regards to solubility of P anions already in the soil solution and/or rhizosphere.

Below are only a couple of quick references I have handy, I will put together other references for you. I think the weak acids I listed above are the same weak acids the Luebkes (e.g. Controlled Microbial Composting) refer to in terms of roots exudates that can solublize some organic matter.

Here is a good quote from the paper: Bioavailability of soil inorganic P in the rhizosphere as affected by root-induced chemical changes: a review
References:

1. Bioavailability of soil inorganic P in the rhizosphere as affected by root-induced chemical changes: a review
Philippe Hinsinger
Plant and Soil 237: 173–195, 2001.
(full text) http://www.plantstress.com/Articles/...ailability.pdf


2. Effects of root exudates on nutrient availability in the rhizosphere
A. Gransee
Plant Nutrition Developments in Plant and Soil Sciences, 2002, Volume 92, Symposium 9, 626-627,
(abstract only for now) http://www.springerlink.com/content/n216w5006k27754p/


3. The release of root exudates as affected by the plant physiological status
R. Pinton, Z.Varanini, Z. Nannipieri (eds.)
The Rhizosphere: Biochemistry and organic substances at the soil-plant interface. Marcel Dekker 2000.
(full text)
http://www-mykopat.slu.se/Newwebsite...nRoemheld2.pdf


4. Root exudates as mediators of mineral acquisition in low-nutrient environments
Felix D. Dakora1,3 & Donald A. Phillips
Plant and Soil 245: 35–47, 2002
(full text) http://www.fsl.orst.edu/~bond/fs561/references/Dakora and Phillips 2002 %20Root%20exudates.pdf


5. Carbonic Acid Decomposition
Richard E. Barrans Jr., Ph.D.
Assistant Director
PG Research Foundation, Darien, Illinois
(full text) http://www.newton.dep.anl.gov/askasc.../chem99661.htm


6. "Ecosystem Physiology: The Plant-Microbe Dance"
(I do not agree with everything written in this reference, but the info about carbonic acid is sound)
by Leslie H. Kirkegarrd
(full text) http://grow-orchid-grow.com/science_...obe_Dance.html


7. "A Touch of Chemistry"
http://www.treedictionary.com/DICT2003/shigo/CHEM.html


8. "Troubles in the Rhizosphere"
http://www.treedictionary.com/DICT2003/shigo/RHIZO.html


9. Plants parasitic on fungi: unearthing the fungi in myco-heterotrophs and debunking the ‘saprophytic’ plant myth
JONATHAN R. LEAKE
Mycologist, Volume 19, Part 3 August 2005.
(full text) http://www-mykopat.slu.se/Groningen/Leake.pdf


10. Myco-Heterotrophs: Hacking the Mycorrhizal Network
Peter Werner
Mycena News, March 2006
(fell text) http://www.mykoweb.com/articles/Myco-Heterotrophs.html

Thanks TF, I was looking for that is spurrs posts. I forgot it was VG:

V

Anyone squeeze a lime into their water? I've done this on occasion without ill effects but don't know if it helped.

I do not like to add in any real amounts humic, fulvic, or citric acid. They are all chelates. They can all be detrimental to soil microlife. Chelates also "force feed" plants much like in hydro/chem setups.

I prefer to have a soil mix that is high in microlife without chelates, the plant can simply "feed' when it wants to, I think the plant is smarter than me, so why would I tell it when to eat?

Just my humble opinion.

Rocky

I want to correct something I wrote in my older posts, which VG quoted in the other citric acid thread: citric acid does not chelate phosphates. Citric acid can chelate other ions though, ex., cations such as Ca, Al, etc.

There are various benefits to using citric acid with organic growing besides to reduce pH* of water, ex.: (1) dissociation of insoluble ionic bonds such as P-Al, P-Ca, etc., thus making P soluble (i.e., plant available) and chelate the cations; and (2) mineralization of P from some organic matter such as soft rock phosphate (due to reasons such as lower pH of soil/soilless solution and direct affect of citric acid on SRF).

I for one like to reduce the pH of water to ~6.0-6.5, even in biological-organic growing, via citric acid, for the reasons above. Citric acid is a normal exudate from roots and many microbes, so it's already in the soil/soilless solution and rhziosphere; that means we won't 'hurt' soil/soilless biota with citric acid as long as we don't over apply.

* As we all know, the pH of water isn't uber important, it's the pH of the soil/soilless solution and rhziosphere that is important, and that is affected to a high degree by water alkalinity, types of nitrogen, etc., not water pH per se.

Hey Spurr;

I do think that Rocky's point deserves some consideration even though it is somewhat mis-applied [eg. all chelates]

Citric acid is a normal exudate from roots and many microbes, so it's already in the soil/soilless solution and rhziosphere; that means we won't 'hurt' soil/soilless biota with citric acid as long as we don't over apply.

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when something is a normal root exudate, how does that relate to the wisdom of applying it directly, vs giving plants the opportunity?

rckymtnthuglife said:

I do not like to add in any real amounts humic, fulvic, or citric acid. They are all chelates. They can all be detrimental to soil microlife. Chelates also "force feed" plants much like in hydro/chem setups.

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I am not sure why you do not wish to chelate ions in media, it's always a great thing to do. Granted, humic acid, fulvic acid and citric acid *can* be detrimental to media biota, but that is only when they are over-applied. They all offer more pluses than minuses, when properly applied.

Chelated ions do not force feed plants, but chelated ions do help keep said ions plant (and microbe) available, much more so than non-chelated ions. And that's a good thing.

There is no (or very little) difference between growing using biological-organics (i.e., soil foodweb and microbial loop, as well as OM mineralization) and conventional methods, in terms of ions. Both are used to provide ions to plants so the plants will grow. The same ions are proffered by microbes, that are given by conventional growers (in most cases). So there is no difference between feeding via microbes or 'chems', besides the ppm of elements in media. In fact, feeding via microbes often means more ions will be chelated than feeding via chems, in most cases. That is because with 'chems' it's normally only metals that are chelated, ex., Fe, Mn, etc., but with organics the microbes themselves can/do chelate many elements such as Fe, Mn, Ca, Mg, etc.

rckymtnthuglife said:

I prefer to have a soil mix that is high in microlife without chelates ...

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That isn't really possible because many microbes themselves will chelate some ions via microbial exudates.

Microbeman said:

Hey Spurr;

I do think that Rocky's point deserves some consideration even though it is somewhat mis-applied [eg. all chelates]

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Hey buddy!

I agree, I already respond to Rockey just above this post. Granted what I wrote is only how I understand the issues, so I am open to debate

P.S. Did you get the computer/driver issue worked out for the new camera software?

mad librettist said:

when something is a normal root exudate, how does that relate to the wisdom of applying it directly, vs giving plants the opportunity?

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It has to due to concentration. Roots and microbes normally do not 'emit' citric acid in enough quantity to have optimal affect. See data regarding white lupin, IIRC, in terms of high exudation of citric acid. Check out VG's citric acid thread wherein I wrote about that topic a little. White lupin is known for some of the highest exudation of citric acid in the plant Kingdom.

Ex. of this topic in regard to P, Ca, Fe, etc.:

Dinkelaker, B., Romheld, V., Marschner, H. (1989). Citric acid excretion and precipitation of calcium citrate in the rhizosphere of white lupin (Lupinus albus L.). Plant, Cell & Environment, Volume 12, Issue 3, pages 285–292

• note: "proteoid roots" = cluster roots

It will remove the chlorine in your water

It has to due to concentration. Roots and microbes normally do not 'emit' citric acid in enough quantity to have optimal affect.

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that's what I don't understand... what "optimal effect"? cannabis with a good mulch and some companion clover seems to have all it needs... I'm doing things to slow them down so I don't have a bottleneck going into the flower room.

what's going to happen to my plants if I add citric acid?

hey chefro420,

I believe you are referring to ascorbic acid, not citric acid. Ascorbic acid is very good at eliminating chlorine (Cl) and chloramines. Granted, citric acid can be effective in eliminating Cl (Swenson, n.d.) but not always in a manner we would like (Streichera, et al., 1986); which is why using ascorbic acid is preferred, IMO anyway. Also, IIRC, it takes some time (hours?) for citric acid to eliminate Cl and but ascorbic acid is immediate.


Refs:

Swenson, J. (n.d.). Citric Acid and Chlorine. Argonne National Laboratory, Division of Educational Programs.

• (good chemistry explanation) http://www.newton.dep.anl.gov/askasci/chem07/chem07368.htm

Streichera, R.P., Zimmera, H., Berczb, J.P., and Colemanb, W.E. (1986). The Interactions of Aqueous Solutions of Chlorine with Citric Acid. A Source of Mutagens. (A Preliminary Report). Analytical Letters, Volume 19, Issue 5 & 6, Pages 681 - 696

spurr said:

Hey buddy!

I agree, I already respond to Rockey just above this post. Granted what I wrote is only how I understand the issues, so I am open to debate

P.S. Did you get the computer/driver issue worked out for the new camera software?

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I believe that something which needs to be considered in the scenario/cycle is the timing of dormancy [& inter bacterial/archaeal communication] amongst the soil biota in 'balance' with the sequestering of organic nutrients/molecules and [as Mad noted] the timed needs of surrounding flora/roots. I do not know if anyone has punched this into the equation. I sincerely doubt that nature has arranged it so that a microbial population multiplying out of control would result in excessive soluble [ionic] nutrients. [outside of disease situation]

Something I'm unsure of because of differing applications of the word; does 'chelated' equate even steven to 'ionized' ?

PS. No but think I've figured out that The manufacturers have failed to remove the old link in for the registry for old camera and driver and/or have failed to designate the new ones. They need to redo the software with a windows registry key specific to the new driver. I've told them this but in the interim am formatting my Vista and installing Windows 7 so I have a fresh OS to test the cameras on.

Re chlorine (Cl):

Cl is often considered an essential element for higher plants in terms of nutrition where it collects (mostly) in chloroplasts. From plant tissue assays of healthy plants, it is not uncommon to find about and greater than 2 ppm Cl. Low levels of Cl (ex,. < 0.1 ppm) in fertigation water is beneficial to plants. Cl (as chloride) is ubiquitous in nature (ex., top soil), mostly as the salt NaCl (sodium chloride). Often in top soils closer to the sea chloride can be found in concentrations up to 10 ppm ...

mad librettist said:

that's what I don't understand... what "optimal effect"? cannabis with a good mulch and some companion clover seems to have all it needs... I'm doing things to slow them down so I don't have a bottleneck going into the flower room.

what's going to happen to my plants if I add citric acid?

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They are going to smoke YOU!

All kidding aside, the efficacy of additional citric acid will vary depending upon media type, media moisture status, plant health, etc. In most cases for us (re media that is already close to ideal in terms of P, etc.) the benefits will not necessarily be visible on plant growth, but that doesn't mean it's not worth doing.

I do not think a grower must use citric acid, but I think it's helpful to do so; YMMV.