Cation-exchange capacity

The carbon nitrogen ratio as well helps give you some indication of the quality of those carbon stocks.

And CEC is another one that was there.

That's a really good indicator.

It doesn't really change, so you don't need to test it as often.

But when you know it, it's handy because a low CEC tells you that the soil isn't really going to be very good at holding nutrients.

So putting really large applications of positive, like cations, like potassium, say, out before at the end of the kind of before the winter period.

Like if your CC is low, the likelihood is that will leach.

Okay.

And that would be cation exchange capacity, CEC, and that's one that just is the ability of the soil to exchange nutrients with the plant, to p- cation, ca- cationic nutrients, positively charged nutrients with the plant.

That's affected by compost, organic matter I should say, compost is one part of that, and soil type.

That, that's just one that's usually shows up and it's one that you can monitor over time.

So in his soil, if he's getting even, you know, a fair amount of rain, uh, or even l- not a lot of rain, it's probably still going to leach away.

So that's where we say, okay, eight CEC can only at any one time hold about 80 pounds.

And so in this type of soil, this is where we would usually want to split apply.

And so that's, that's one of the things that's really important.

This is the middle of the month podcast, September 15th, 2026, where we will focus on just one aspect of gardening.

This month, that one aspect is cation exchange capacity, CEC as it is abbreviated.

and it is the soil's nutrient storage capacity.

The information that I will be sharing with you is grounded in science, backed by research, and it is tailored specifically for those of us gardening in South Central Texas, although it would apply all over.

Calcium, for example, as the cation exchange capacity of the soil changes, then the quantity of nutrients in it also changes.

So if you've got a soil with a CEC of, say, 15, the amount of calcium that should be in that soil, exchangeable calcium, might be in the order of 25 or 2,800 kilograms per hectare.

And for people listening, is a 15 CEC, is that high or low? It's in Australian conditions, it's

medium to high.

Okay.

Depends where you are.

I've got clients in some areas that have CECs of 55 and 65, really rich soils.

And in some areas, particularly Western Australia, which is typically very sandy soil, the CEC might only be three.

Yeah.

You know, Kyle, one other thing I wanted to bring up on that point is depending on what your cation exchange capacity is or your CEC, does that change how important this is too? Because in like a sand deer soil, you want that to try to hold some nutrients in there.

So would it benefit more to have a little bit higher magnesium soil? What about the different CECs? Does that change your recommendations?

Yeah.

The higher the clay content, usually the higher our CECs will be.

And especially in high clay content, we can expect those to be more like two to one clay.

So they kind of have these inter layers that hold on and trap magnesium into.