I was helping a friend today review his soil tests. He has increased OM and CEC, in soil that was ranking more towards, sand on the CEC scale. I self admittedly, just couldn't articulate CEC very clearly at that moment. I was upset with myself and started reading again for a refresher - I am glad I did.
I have always thought it is important to monitor but I don't get overly hung up on it. My personal opinion on CEC is to use it as a focal point of your soil tests, only to ensure you are not seeing major variances from one year to the next - if that does occur, that is a red flag that something with the test didn't go correctly. Similarly, I don't want to see OM increase or decrease by impossible metrics, PH, etc.
So I started to refresh my memory on some CEC articles and found this one below that is very interesting and easy to comprehend. As
@giles says here are the cliff notes!
1. CEC defines the soil make up - clay-sand
2. CEC stands for - Cation exchange Capacity
3. Cations are held by the negative charges in the soil - the higher the CEC (typically higher OM's are correlated with higher CEC, HUMUS has a CEC of 50) - the more negative IONs and their ability to hold positive charges. The most common positive charges held in the soil as OM and CEC increase, are Ca++, Mg++, K++, etc. (calcium, magnesium, and potassium - these are Cations)
4. As you see increasing OM, helps to hold more nutrients and make them bioavailable to the plant.
5. This is why in the long run, you should need less and less lime, fertilizer, etc. Through the diversity of planting and symbiosis occurring, you will be holding more minerals/nutrients in the soil. Ray A, talks about this happening through the soil aggregates being formed, the soil pores also formed allowing soil microbes to get through the soil to the plant and back.
See the link below for a lot better and more clear information, than I am able to provide.
www.dpi.nsw.gov.au
Thank you for following along.
AT