Thanks Brian for your thoughts. Concerning K I have only ever used compost and K sulphate on my property. I would never use K chloride. I have read about two different methods in obtaining CEC value, a scientific test that gives you the value, and a calculated method. I’m not familiar with the scientific method and it’s accuracy or how much it might differ from the calculation method. I think I’ve read that most labs just calculate it.

Now with what you said that makes perfect sense to me based on the concept of CEC but I don’t see this in reality. Here are some examples:

In my 5000 sqft plot I have two distinct areas of soil. This is because it was trucked in. One has a pH of about 6 and organic matter % of 7 with a CEC of 7 (1000ppm of Cal). The other has a pH of 7.5 with organic matter of 4% and a CEC of 9 (1600 ppm cal). Both have the same sand base but the higher CEC soil has 3% less organic matter. This doesn’t make any logical sense to me. The only reason the one is higher is because it has more calcium. I don’t believe the capacity is actually greater in this soil. It may be currently holding more nutrients because of the excess calcium, or possibly a lack of other nutrients that would balance it. Time will tell if this soil calcium will come down to meet other minerals or if I can bring up other minerals to meet it there no longer showing excess calcium. Working on bringing pH down on it now. More.

Now I have many different fruit trees on my property grown in the same Sandy soil with 6-7% organic matter. The soil came from the same source. I have to raise my growing areas up because of very high water table. These soils typically have a pH of 6.8-7.2 but the calcium levels are even higher than my high pH garden(2300-2500ppm of Cal). These soils have a CEC of 12-15. Some of the excess calcium in these soils is from mistakes I made 2-5 years ago. I don’t believe that these soils have a greater capacity to hold minerals than my low pH soil that has a CEC of 7. The only difference is excess calcium has raised the number to 12-15. I don’t believe there is anything about the soil itself that gives it a better holding capacity than my other soils, same sand and same amount of organic matter. Im pretty confident from experience with this soil and the evidence of using it that if I added a bunch of lime to my soil that has a CEC of 7 it would hold brining the CEC up to 12-15 and 3-4 years from now the soil test would still say it’s a CEC on 12-15.

It doesn’t make sense to me that adding minerals would increase the CEC but the evidence I see on my property is that this is exactly what happens. This is why I’m posting to see what others have to say because I’m not finding in my context that the idea of CEC is you got what you got and if you want it to be higher you need more OM or clay added. I’m suggesting that something seems very wrong with the CEC calculation method. It seems to show what is currently being held but not what the real capacity is. Either that or I am misunderstanding something. This is why I have brought this up on here for discussion.