Best amendment for increasing cationic exchange capacity?

[moses wellfleet]

I have access to bentonite for this purpose. But what are the other options, kaolin perhaps... And what are the disadvantages to watch out for?

This would be for indoor no till/recycled soil. The mix is close to Cootz' mix except I still use dolomite and calcitic lime!

 

[SpicySativa]

Worm castings (and associated humus) will increase CEC. As will biochar, or just about any clay.

Do you feel your CEC is lacking for some reason?

 

[bigshrimp]

I believe zeolite has the highest CEC of mined mineral amendments.

i believe...

 

[bigshrimp]

People have reported issues with using expanded/calcined clays as a primary aeration component. They also have different qualities depending on source material and firing temp.

 

[moses wellfleet]

Worm castings (and associated humus) will increase CEC. As will biochar, or just about any clay.

Do you feel your CEC is lacking for some reason?

No not at all I am happy with my results, but always looking for ways to improve.

So any type of clay will improve CEC to some degree?

 

[SpicySativa]

That is my understanding. But... depending on you soil structure, adding clay may do more harm than good. (I know you know this...)

 

[Hauna]

No not at all I am happy with my results, but always looking for ways to improve.

So any type of clay will improve CEC to some degree?

CEC is increased with surface area, the finest (and largest surface area per unit) soil textural class is clay.

 

[Hauna]

Make sure you look at the soil triangle and keep your soil proportions in the desired soil class.

 

[Weezard]

When it comes to CEC, it's hard to beat coco coir.

Aloha,
Weezard

 

[LilMan72003]

clay-humus crumb

 

[OrganicBuds]

When it comes to CEC, it's hard to beat coco coir.

Aloha,
Weezard

Peat beats coco every time with quality peat vs quality coco regarding CEC. I find my mix's CEC goes up with high quality EWC. I also find pumic to be higher in CEC than perlite, that will up your numbers slightly.

 

[mapinguari]

I like to go in the woods and harvest (small) patches of forest duff. We have clay-based soil here on the west slope where the Sierras and Cascades meet, and there is a layer where you can see it getting taken up by fungal hyphae and formed into a crumbly mat.

If you don't have a situation like this right nearby, consider spending your money on some gas to go get it, rather than giving the money to a store for a packaged product.

 

[Granger2]

How are you measuring CEC in peat, coco, etc.? -granger

 

[vapor]

a medium is. and certain amendments increase said abilities.
https://en.wikipedia.org/wiki/Cation-exchange_capacity

organic matter/clay.

 

[MIway]

vermiculite has good cec

 

[EclipseFour20]

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!

 

[habeeb]

"And remember air/water porosity rates are very, very, very important for a "balanced" grow medium!"

coco comes to mind....

 

[bigshrimp]

Vermiculite seems ideal, except it is too delicate - collapsing after a couple remixes. In a no till situation i would consider it a good amendment.

Chunky verm has been mentioned a couple of times, something i'd like to get my hands on. Depending on its durability, it could be a great CEC addition.

 

[dr.penthotal]

many good advices in here.
you're pointing in right direction. first get the most cec available for your mix, keeping in mind to have enough drainage and overall porosity of the mix.
Cec can be measured in a lab. it's on this that you'll be balancing proper ca:mg:k:na proportions and quantity. as well as P and S balance...
EWC, coco, vermiculite, pumice, biochar and clays like zeolite, bentonite are good choices. don't go over an 7-8℅ on with clays in your mix.

 

[moses wellfleet]

Thanx for all the helpful replies, I did some research and can now explain myself better.

Organic matter in the soil such as compost and vermicast is negatively charged, and most trace elements are positively charged. But phosphorous is also negatively charged, thus it is repelled by the organic matter and allowed to leach out of the soil because it is not attached to anything.

So i am told that the bentonite is positively charged, and will create sites for the phosphorous to bond to the soil. So if I amend the soil with a little bentonite I should be making much more efficient use of the phosphorous that I am feeding to the soil... Am I understanding things correctly?