Best amendment for increasing cationic exchange capacity?

[dr.penthotal]

CEC is like 'hands' in soil... the more, the more hands you have to 'hold' some nutrients directly available to plants.
as CEC is Cation Exchange Capacity, we're talking about the positively charged ions. so Ca, Mg, K, Na and H are the most abundant and play the major role in occupying CEC.
the ion phospate is an anion, and has a different path of being taken up by plants.
phosphate is really bond into soil and usually unavailable, we need fungi and their enzymes to let it available. anions are really soluble when in ionic form and can be leached away if proper soil life is missing (ie little organic matter or the abundant use of chemocals that destroy the soil life..)
the point is to develop a rich complex enviroment where life is at his full throttle and will take care of all the nutrients if in balance.
cations are attached to a mineral part, anions are dealt by livings. In a no till system I wouldn't bother much on every nutrients, I push the life in it to deal with it automatically. just remember to add different sources of the same nutrient and correct amounts.
I wouldnt' use kaolin, among the clays it has the worst cec. better option would be zeolite.
bentonite is good and negatively charged as well. but it's useful as well as a water reservoir. it enhanches the power of the soil to retain water (it's used as cat litter to absorb smell and urine)
don't add more than 1-2% of the overall mass.
hope this helps

 

[entheogen]

What about shrimp or crab meal?

 

[moses wellfleet]

The bentonite becomes like snot when you add water to it!

 

[EclipseFour20]

The bentonite becomes like snot when you add water to it!

Try the "calcined" variety--it retains its chunky shape when wet. OilDri--25lb bag at Walmart for less than $5 (auto dept) is what I use....and I add about 6% (by volume) to my custom grow medium.

BTW...growing mediums with high CEC rates require significant less fertility, assuming the soil PH is correct.

Cheers!

 

[moses wellfleet]

Try the "calcined" variety--it retains its chunky shape when wet. OilDri--25lb bag at Walmart for less than $5 (auto dept) is what I use....and I add about 6% (by volume) to my custom grow medium.

BTW...growing mediums with high CEC rates require significant less fertility, assuming the soil PH is correct.

Cheers!

I'm not saying the snot like consistency is a bad thing, I can see how it would improve moisture retention in the soil. But too much would clearly be a disaster for soil stucture...

 

[EclipseFour20]

Here is a calcined clay study that got me thinking a few years ago. Their sweet spot was 12% (way too much for my mix). Very interesting!

Cheers!

 

[VortexPower420]

Compost, bark, peat, and coco coir are "organic" sources that have good CEC capacities--but the CEC is temporary and will disappear if the soil PH is out of whack. The acidic function that causes the "temporary" CEC relationship between "organic matter" and roots...occurs ONLY IF the soil PH is "correct".

Clay products (montmorillonite being the best), diatomaceous earth, and other "mineralized aggregates" are "inorganic" sources that have good CEC capacities. Since the minerals are sourced from the clay fractions (not from any acidic process) the CEC capacity is "permanent", but all will be lost if the soil PH is not "correct".

Clay products with high CEC include: Vermiculite, calcined clay (I like the oil absorbent, OilDri--25lb bag, less than $5 @ WalMart) and powders (kitty litter).

Using clay products will also increase Anion exchange capacities (opposite of cation)--not so much with "organic" matter, which probably is a good reason to include both "organic" and "inorganic".

The importance of "soil PH" can not be discounted! And remember air/water porosity rates are very, very, very important for a "balanced" grow medium!

Cheers!

I was wondering where you got this information? I was always under the assumption that Clay only holds Cations and humus is what can also hold on to Cations and Anions.

I was under the impression that the best way to get P available to you plants is to bind in in the stable humic material. Such as composting rock phosphate first. P is one of the most reactive elements we deal with it will make over 100 different combinations some incredibly strong.

Explain to me the first paragragh, how is the humus CEC only temporary and how does soil "pH" have anything to do with. What is acid function?

The only acid function I can think of is the effect it has on clays at very low pH. When you get down to the 5 pH range the acidity will start breaking apart the clay structure and release Al in toxic amounts. Whn this is happening you are going down in classes of clays what was Montmorillonite will turn into Kaolinite. In effect lowering the CEC of the clay greatly because of the strong acid breaking down the silicate sheets[FONT=Arial, Helvetica, sans-serif]


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[VortexPower420]

BTW...growing mediums with high CEC rates require significant less fertility, assuming the soil PH is correct.

Cheers!

Says who? Dr. P's got it right, but i like the food on the shelf analogy. There is the food on the plate which is what has been made soluble through microbial action and/or root exudes and the CEC is like the food in the pantry for later.

So... using this thought the higher the CEC the more room for food in the pantry. Any free space in the pantry will be filled up with H ions (low pH) what needs to be done at that point is to fill the shelf with food 65% Ca, 15% Mg, 5% k and 5% Na leaving only about 10% free spaces for H.

The plant freely exchanges H in trade for Ca, Mg ,K, Na from the soil colloid. As the plant "eats" the pH goes down.

The higher TCEC you have the more fertility you will need to fill those sites other wise you have low pH.

pH is not a acidity issues it is a fertility issue.

Just sayin...

Timbuktu

 

[EclipseFour20]

Vortex--

I too thought soil's PH and CEC were independent concepts, but I was wrong. They work hand in hand and are part of a more complex system. I came across this online text book (out of print and published in 1988) and it provided the simplest explanations about soil that I have ever read...simply titled, Soil Fertility.

Source: soilanalyst.org/wp-content/uploads/2012/07/Foth-1.pdf
Some cut and paste from Chapter 2, Ion Exchange:

D e t e r m i n a t i o n of Cation E x c h a n g e Capacity
The amount of CEC or negative charge of a soil is pH-dependent. For
example, the H of various acidic groups of soil organic matter may be
neutralized by O H – , which results in the formation of water and an unsatisfied
negative charge. As soil pH increases, so does OH– concentration (or
activity) and the formation of water and negative charge or CEC. For this
reason the CEC must be determined at a standard pH to make valid
comparisons between soils.
Commonly, the soil is treated with a normal ammonium acetate solution
adjusted to pH 7.0. Ammonium replaces the adsorbed cations and
occupies the exchange sites. The excess ammonium, along with the exchanged
or displaced cations, is leached out with alcohol adjusted to pH
7.0. The amount of ammonium retained by the soil is then measured and
equated to the CEC. Another procedure determines CEC at pH 8.2 using
NaOAc and BaCl2 plus triethanolamine (TEA) solution. The NaOAc replaces
exchangeable Ca, Mg, K, and Na, which are measured and added to
the amount of acidity neutralized by the TEA. Another method uses an
extracting solution of unbuffered KC1 or CaCl2 to replace the exchangeable
cations and leach them from the soil. Then the amount of each exchangeable
cation in the leachate is determined, and the sum of the cations is
equated to the CEC. This method is very important for determining the
CEC of soils at their present or natural pH, particularly, for acid soils.

SOURCE A N D A M O U N T OF N E G A T I V E CHARGE
Organic matter and clay fractions are the source of most of the negative
charge. T h e negative charge of the soil organic matter, SOM, is pH-dependent,
and the negative charge of t h e clay fraction is both pH-dependent and
permanent.

N e g a t i v e Charge of O r g a n i c Matter
Organic matter has several acidic functional groups that dissociate H+ or
deprotonate. About 85 percent or more of the negative charge is due to
carboxyl and phenol groups. In the pH range of most soils (pH less than
8.0), carboxyl groups provide most of the CEC of SOM:
COOH = COO– + H+ (2.2)
A small amount of charge comes from enolic and imide N groups.
An increase in hydroxyl concentration of t h e soil solution, accompanying
an increase in pH, brings about a greater dissociation of adsorbed H + ;
more water forms, and the CEC increases. As a result, the CEC of organic
matter is pH-dependent or variable (CECv).
Both living roots and dead organic matter have CEC. As organic
matter decomposes in the soil, there is an increase in acidic groups, which in
turn increases the CEC. Histosols are composed mainly of organic matter
and have relatively high CEC, typically between 100 and 200 m e q / 1 0 0 g.
Fibrists are fibrous Histosols and are the least-decomposed or most peaty
Histosols with a CEC of about 100. The Saprists, the most-decomposed
Histosols, have a CEC more nearly 200. T h e bulk of humus in mineral soils
is generally well decomposed and has quite high CEC averaging about 200
and ranging from 100 to 400. Thus, the degree of decomposition of soil
organic matter greatly affects the CEC.

N e g a t i v e Charge of Mineral Fraction
The minerals of the clay fraction are the source of most of the negative
charge of the soil's mineral fraction. The negative charge is both pH-dependent
and permanent. Isomorphorus substitution produces permanent
CEC (CECp), and the CECv is due mainly to deprotonation of edge or
exposed hydroxyls.

Origin of Clay Minerals in Soils
Clay minerals are formed by the weathering and alteration of existing
minerals or by neogenesis, the crystallization of ions from solution. Soils
formed from sediments and sedimentary rocks inherit clay minerals present
in these materials. In the glaciated North Central region of the United
States, the major clay mineral in the loess is montmorillonite (a smectite)
and in the till hydrous mica (illite). Many of the till-derived soils of this
region have a significant amount of hydrous mica inherited from the till
and vermiculite that was produced by the alteration of hydrous mica.
Mollisols of the Corn Belt that developed from loess have clay fractions
dominated mostly by montmorillonite, for this clay was inherited and has
not been substantially altered or destroyed. Vertisols of the Deccan Plateau
in India, by contrast, contain montmorillonite that formed from the weathering
of underlying basalt (neogenesis). Thus, the formation and alteration
of clay minerals in soils are complex. Our consideration of the origin of the
negative charge will focus on the generally accepted weathering sequence
of mica to hydrous mica to vermiculite and smectite to kaolinite and, finally,
to gibbsite. The weathering sequence approach provides a unifying concept
about the origin of clay minerals and the source and amount of their
negative charge.

Why are less ferts required with high CEC soils? Less leaching--think of buckets. Low CEC (small buckets)--high CEC (big buckets). As ferts are applied to the soil, these buckets capture certain elements/ferts/nutes and hold them. The small buckets empty sooner (low CEC) and require frequent filling (more applications)--whereas the big buckets (high CEC) have a bigger capacity and do not need refilling as often (less applications). Leaching occurs when the buckets are "full" (no more capacity) and one "fertilizes" (money down the drain). So...low CEC--more applications of ferts/nutes....high CEC--less applications of ferts/nutes. Some may argue a greater amount of ferts/nutes will be required for high CEC soils (since bigger buckets hold more) and this is may be true to most outdoor farmers/gardeners, but in the "containerized indoor garden world" this may not be true. Big difference, unlike outdoor gardeners/farmers that fertilize their soil for more than one growing season, container growers do not fertilize the "current crop" containers with the "next crop's" fertility...rather, we use fresh grow medium for each crop. Another way of looking at it--CEC does not effect the plant's nutrient requirements (they do not change)--rather CEC effects the soils ability/efficiency to hold certain elements in the grow medium (which does change). So when it comes to fertility....less can be "be$t"

For a more scientific explanation--google: fertilizer application "high CEC". Lots out there--but I like the bucket example, easier for us "non-scientific" guys to understand.

Cheers!

 

[vapor]

check out the book by Agricola/Astera, Ideal soil.

 

[VortexPower420]

Vortex--

I too thought soil's PH and CEC were independent concepts, but I was wrong. They work hand in hand and are part of a more complex system. I came across this online text book (out of print and published in 1988) and it provided the simplest explanations about soil that I have ever read...simply titled, Soil Fertility.

Source: soilanalyst.org/wp-content/uploads/2012/07/Foth-1.pdf
Some cut and paste from Chapter 2, Ion Exchange:

D e t e r m i n a t i o n of Cation E x c h a n g e Capacity
The amount of CEC or negative charge of a soil is pH-dependent. For
example, the H of various acidic groups of soil organic matter may be
neutralized by O H – , which results in the formation of water and an unsatisfied
negative charge. As soil pH increases, so does OH– concentration (or
activity) and the formation of water and negative charge or CEC. For this
reason the CEC must be determined at a standard pH to make valid
comparisons between soils.
Commonly, the soil is treated with a normal ammonium acetate solution
adjusted to pH 7.0. Ammonium replaces the adsorbed cations and
occupies the exchange sites. The excess ammonium, along with the exchanged
or displaced cations, is leached out with alcohol adjusted to pH
7.0. The amount of ammonium retained by the soil is then measured and
equated to the CEC. Another procedure determines CEC at pH 8.2 using
NaOAc and BaCl2 plus triethanolamine (TEA) solution. The NaOAc replaces
exchangeable Ca, Mg, K, and Na, which are measured and added to
the amount of acidity neutralized by the TEA. Another method uses an
extracting solution of unbuffered KC1 or CaCl2 to replace the exchangeable
cations and leach them from the soil. Then the amount of each exchangeable
cation in the leachate is determined, and the sum of the cations is
equated to the CEC. This method is very important for determining the
CEC of soils at their present or natural pH, particularly, for acid soils.

SOURCE A N D A M O U N T OF N E G A T I V E CHARGE
Organic matter and clay fractions are the source of most of the negative
charge. T h e negative charge of the soil organic matter, SOM, is pH-dependent,
and the negative charge of t h e clay fraction is both pH-dependent and
permanent.

N e g a t i v e Charge of O r g a n i c Matter
Organic matter has several acidic functional groups that dissociate H+ or
deprotonate. About 85 percent or more of the negative charge is due to
carboxyl and phenol groups. In the pH range of most soils (pH less than
8.0), carboxyl groups provide most of the CEC of SOM:
COOH = COO– + H+ (2.2)
A small amount of charge comes from enolic and imide N groups.
An increase in hydroxyl concentration of t h e soil solution, accompanying
an increase in pH, brings about a greater dissociation of adsorbed H + ;
more water forms, and the CEC increases. As a result, the CEC of organic
matter is pH-dependent or variable (CECv).
Both living roots and dead organic matter have CEC. As organic
matter decomposes in the soil, there is an increase in acidic groups, which in
turn increases the CEC. Histosols are composed mainly of organic matter
and have relatively high CEC, typically between 100 and 200 m e q / 1 0 0 g.
Fibrists are fibrous Histosols and are the least-decomposed or most peaty
Histosols with a CEC of about 100. The Saprists, the most-decomposed
Histosols, have a CEC more nearly 200. T h e bulk of humus in mineral soils
is generally well decomposed and has quite high CEC averaging about 200
and ranging from 100 to 400. Thus, the degree of decomposition of soil
organic matter greatly affects the CEC.

N e g a t i v e Charge of Mineral Fraction
The minerals of the clay fraction are the source of most of the negative
charge of the soil's mineral fraction. The negative charge is both pH-dependent
and permanent. Isomorphorus substitution produces permanent
CEC (CECp), and the CECv is due mainly to deprotonation of edge or
exposed hydroxyls.

Origin of Clay Minerals in Soils
Clay minerals are formed by the weathering and alteration of existing
minerals or by neogenesis, the crystallization of ions from solution. Soils
formed from sediments and sedimentary rocks inherit clay minerals present
in these materials. In the glaciated North Central region of the United
States, the major clay mineral in the loess is montmorillonite (a smectite)
and in the till hydrous mica (illite). Many of the till-derived soils of this
region have a significant amount of hydrous mica inherited from the till
and vermiculite that was produced by the alteration of hydrous mica.
Mollisols of the Corn Belt that developed from loess have clay fractions
dominated mostly by montmorillonite, for this clay was inherited and has
not been substantially altered or destroyed. Vertisols of the Deccan Plateau
in India, by contrast, contain montmorillonite that formed from the weathering
of underlying basalt (neogenesis). Thus, the formation and alteration
of clay minerals in soils are complex. Our consideration of the origin of the
negative charge will focus on the generally accepted weathering sequence
of mica to hydrous mica to vermiculite and smectite to kaolinite and, finally,
to gibbsite. The weathering sequence approach provides a unifying concept
about the origin of clay minerals and the source and amount of their
negative charge.

Why are less ferts required with high CEC soils? Less leaching--think of buckets. Low CEC (small buckets)--high CEC (big buckets). As ferts are applied to the soil, these buckets capture certain elements/ferts/nutes and hold them. The small buckets empty sooner (low CEC) and require frequent filling (more applications)--whereas the big buckets (high CEC) have a bigger capacity and do not need refilling as often (less applications). Leaching occurs when the buckets are "full" (no more capacity) and one "fertilizes" (money down the drain). So...low CEC--more applications of ferts/nutes....high CEC--less applications of ferts/nutes. Some may argue a greater amount of ferts/nutes will be required for high CEC soils (since bigger buckets hold more) and this is may be true to most outdoor farmers/gardeners, but in the "containerized indoor garden world" this may not be true. Big difference, unlike outdoor gardeners/farmers that fertilize their soil for more than one growing season, container growers do not fertilize the "current crop" containers with the "next crop's" fertility...rather, we use fresh grow medium for each crop. Another way of looking at it--CEC does not effect the plant's nutrient requirements (they do not change)--rather CEC effects the soils ability/efficiency to hold certain elements in the grow medium (which does change). So when it comes to fertility....less can be "be$t"

For a more scientific explanation--google: fertilizer application "high CEC". Lots out there--but I like the bucket example, easier for us "non-scientific" guys to understand.

Cheers!

I be honest I feel what you posted just proved what I said about pH being dependent on the amount of Cations attached. No where did it say anything about anions and the fact that clay is solely responsible for them. Which they are not that is mostly a humus job.

No matter how you slice it a low pH means a lack of nutrient cations and a abundance of H

I guess I differ from you because I reuse my soil and it gets better with age. I am striving for a mineral rich environment where my plant exudes sugars to feed microbes that dissolve minerals and feed my plant in the most available form. I look to fill all of my CEC sites to luxury levels so my plant never needs and I can just sit back and enjoy the ride. A mulch and top dress of this here and there, a drench at Critical points of influence and leave the rest to nature.

I kind of understand your "bucket theory" but I believe that applys more to chem grows then living soil. Useing a low CEC medium in a chem grow and you over feed I get what you mean by money down the drain not to mention the damage to plants from to many soluble nutrients. When if you use a high CEC medium you have more wiggle room and your plant may be able to up take it.

The clay article is on point and the reason we all try and use basalt of other top of the chain rock dusts. Another reason Carbonatite (ultramafic alkali carbonate) is one of my favorites.

Timbuktu

 

[EclipseFour20]

Vortex,

Thought I answered your questions why CEC is temporary for organic matter--permanent for clay, how the acidic function is important to organic sources, and why increased capacity (bigger buckets) allows the usage of less ferts.

Since we both agree that clays hold cations and organic matter (through acidic function--PH) hold both cation and anions, did not feel worthy of "rebroadcasting" this notion.

Sorry if you did not like my "capacity" analogy with "buckets"--but do please explain why you feel it applies to mostly chem grows? What rules change for them? I would think CEC would be applicable to all growing disciplines.

No problem in growing this way or that way--soooo many paths to the same destination. For me, soil cost is not a limiting factor (custom mix) and I rather spend my time/investment/resources on other areas. Glad you recycle your soil--its just not the way I roll.

Cheers!

 

[Granger2]

Humates, especially fulvics. -granger
https://www.icmag.com/ic/showthread.php?t=243151