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On top of Brush Mountain, Pa.

The question here is really this. If your soil has a low cation exchange content and is either made up mostly of sand and silt, what have you done about it? What are you doing to improve the CEC? I added lots of OM and the CEC went up to 18 with around 25% OM. I have no clay in my soil and am thinking about adding some (bentonite) to bring the CEC up to higher levels. IanP has soil with a CEC of 30. I would like to be more like him. Has anyone used clay to increase their cation exchange content and if so, how much.

4/8/2019 2:25:20 PM

Eastern Shore of VA

I don’t think bentonite is a good idea Marv.
I drill wells for water consumption,and we use bentonite in a dehydrated powder as we bore down.
Adding water to it as we drill causes all sand and soil to clump together into a paste.
Think wet concrete.

4/8/2019 9:36:43 PM

Grittyville, WA

Ians is that high because of peat not clay. Peat would be a better choice.

4/8/2019 11:51:14 PM

Grittyville, WA

Oh I didnt read everything you wrote. For tomatoes yes... Sure add clay. Clay is not a bad thing it just requires an understanding of tilth. Which means calcium and magnesium and soil saturation become issue. Pumpkins I would not.

4/9/2019 2:46:49 AM

Grittyville, WA

Overposting here (and Im no expert) but what good is extra CEC if you dont add more cations also? Clay may or may not already have a lot of calcium in it. How would you know if you should add more cations? Another soil test??

4/9/2019 2:52:26 AM

On top of Brush Mountain, Pa.

Esheel, the reason the clay turns into a cement like paste has to do with the balance between the calcium and magnesium in the soil you are dealing with. It is very likely low in magnesium and definitely out of balance. The presence of the bentonite has little to do with it. If you step in the clay soil, the reason the soil sticks to you like glue to your shoes means it is low in magnesium.

4/9/2019 7:22:06 AM

On top of Brush Mountain, Pa.

Anyone know what the OM content of Ians soil is?

4/9/2019 10:35:16 AM

Grittyville, WA

The clay particles align when disturbed when saturated. If you work clay soil when its saturated it loses any porosity. Self discipline is required... And protection from rain is required.

4/9/2019 4:29:02 PM

Eastern Shore of VA

I’m not sure of the magnesium content of the soil,but I know we use bentonite everyday,and you don’t want to get it wet unless you have to.
Once it absorbs the water and becomes a paste it becomes an excellent sealant against water.

4/9/2019 5:09:39 PM

Tinykinville

I think the mistake involved here is assuming the change over to all clay. Clay is fantastic and full of nutrients and has insanely high CEC. So adding some to sand soils would be a great idea as long as done at a reasonable rate there would not be the problems associated with a clay soil.

4/10/2019 2:05:55 AM

Central NY

https://www.maximumyield.com/the-capacity-for-ex-change-cation-exchange-capacity-and-what-it-does-for-your-garden/2/1114
Does this mean that the type of clay you would add is important?...this cEC stuff is above my pay grade...interesting though

4/10/2019 9:24:51 AM

Eastern Shore of VA

I don’t know.
I’m just going by my experience with bentonite.
Not trying to argue with anyone.
Too much fighting on this board anyway.

4/10/2019 11:00:04 AM

Grittyville, WA

That article started out good but I think iy contains a glaring error. I dont think atomic weight is tied to CEC. I think only the electric charge would matter.

There are some complicated chemical concepts that begin to surface. It would be a seriously scientific discussion to answer all the cec questions I have... This topic can certainly sort those who paid attention in chemisty from those who didnt. I think its safe to say we need someone with a degree in chemistry to chime in.

4/10/2019 3:34:51 PM

Grittyville, WA

*it. Speaking of glaring errors... These phones nowadays I know its not just me!

4/10/2019 3:36:45 PM

Grittyville, WA

My guess is bentonite does not come prepackaged with calcium... And thats why it has sticky/slippery physical properties. Total shot in the dark. Winging it here!!!

4/10/2019 3:43:18 PM

Gone With The Win

Will a soil test give a cec?

4/10/2019 8:47:01 PM

On top of Brush Mountain, Pa.

Yes

4/10/2019 10:26:07 PM

Morgantown, WV

Yes Pork chop, there are lots of different types of clay. Some clays swell when wet, then crack wide open when they dry, others do not.

Cation Exchange Capacity (CEC) works like this: + charged particles (your fertilizers) are "cations" which are attracted to the - particles or anions ( your soil). CEC is the ability of your soil to pick excess ions up when you fertilize, and release them as the gradient changes and they are re-wet to move into solution (rain or irrigation).

Sandy soils with low OM have very little CEC as sand is solid and large particle size, so soil drains well with little adsorption through pores. Silty soil has a medium amount of CEC due to smaller particle size and being more porous. Clay has the highest CEC of the 3 types of soil because of its structure and minute particle size.

Organic matter, peat, clay, vermiculite, these are all things that increase CEC by adding more negative ions for the positive ones to grab onto.

4/10/2019 11:45:00 PM

Morgantown, WV

To put it into perspective, our soil professor explained particle size in terms of notebook paper. If a teaspoon of sand equaled one regular sheet of notebook paper worth of surface area front and back, one teaspoon of silt would equal the entire notebook. One teaspoon of clay would equal roughly two full reams of printer paper worth of surface area if the particles were spread to a single layer.

High CEC is good if your soil is balanced, as the plants can pull from a large reservoir of nutrients. If you have deficiencies however, the higher your CEC, the more amendments you will need to cause effect. Small amounts of amendments change sand quickly, while it takes more amendments to make a smaller effect with really high CEC.

This is why, on the soil triangle, you want to have an even balance of each, to get the benefits of each equally. It is incredibly difficult to change your soil physics (whether you have silt loam versus sandy loam, etc.) but it can be done through large additions (25-30%) of your soil. A few 50 lb bags of sand won't make a bit of actual change, but couple dumptrucks would.

4/10/2019 11:55:19 PM

Morgantown, WV

Marv, I'm not crazy about the bentonite either, even mixed well into your soil I feel it will sludge up rather than drain.

Have you considered turface? I feel it would be a good solution for you as it has a similar particle size to perlite, retains aeration, and has good CEC that will not break down easily like OM or even peat. It's what professional turf managers use on ball fields and some golf courses to aid in turf recovery. It can also be purchased fairly cheaply in bulk as you'll need a bit of it I imagine?

4/11/2019 12:02:32 AM

On top of Brush Mountain, Pa.

I will definitely look into turface but to add it to the soil now would involve disturbing the soil a lot and would effect whatever soil life I have. I am no longer tilling and would have to incorporate is in the fall using my broad fork. I need to increase my CEC. Ian uses tons of perlite for aeration and probably has a CEC of nearly 30 from using peat moss. I have never seen any numbers from him for OM.

4/11/2019 7:40:11 AM

On top of Brush Mountain, Pa.

Here is an article about turface. It looks like it is baked clay, very small particles of what is like pottery. It helps the soil in many ways and is an amendment recommended for highly trafficked area like football fields. One recommendation is that your soil in heavy traffic areas be 25% turface. The cost of this would be considerable. And the disruption of your soil aggregates to add this would also be considerable. It is interesting but may be more than I want to do at this point in my life.

https://www.houzz.com/discussions/1898447/turface-as-a-soil-conditioner

4/11/2019 7:54:01 AM

On top of Brush Mountain, Pa.

I went to our local feed store and was very surprised that they had turface on hand. In fact, they sell tons of it to be used to dry up wet spots on baseball and softball fields. And, quite a few gardeners are buying it to raise the cation exchange content in their soil. Why did I not know this. It comes in several forms, basically different sized particles but the one I looked at is almost a dust. I am thinking that I will ultimately be using some of this in my garden to raise the CEC. Maybe some sphagnum peat moss too. If Ian has a CEC of 30 I am thinking I need something higher than 18.

4/11/2019 11:09:31 AM

Grittyville, WA

I think 18-20 is good. Steve Geddes Logan Labs CEC 2018... anyone want to take a guess? 13.8.

4/11/2019 12:05:04 PM

Grittyville, WA

If his roots can go twice as deep because he has porous sand then its all the same in the end. Same quantity of nutrients available... just the roots have to go much deeper maybe.

4/11/2019 12:08:22 PM

Grittyville, WA

Steve Daletas CEC... 24. Credit to sngpg. What great info in their newsletter.

4/11/2019 12:12:30 PM