pH and CEC

pH and CEC

Hi!

In the answers to practice exam question session #2, the answer to question number 3 says high CEC occurs at low pH. I am confused, because I believe high CEC should occur at high pH, since more H dissociate from functional groups on SOM at high pH, thus increasing the CEC. Could you please explain where my thought process goes wrong?

BlaiseMatlock (talk)02:23, 20 March 2020
Edited by another user.
Last edit: 03:00, 20 March 2020

Please read the provided answers carefully.
Question 3: What soil properties enhance nitrate (NO3-) leaching losses from soil?
1. Humic climate 2. Significant nitrate in the soil 3. Coarse texture 4. Low AEC
although we recognize that the wording may not be very clear in relation to AEC

MajaKrzic (talk)02:46, 20 March 2020

This is the quote I am referring to "Soil properties that would enhance nitrate (ie an anion) leaching are: ... High CEC (which also means low AEC), such as soils high in clay + high in OM at low pH ".

It is totally possible that I have simply misinterpreted this sentence. Could you explain what this sentence means?

BlaiseMatlock (talk)02:52, 20 March 2020
Edited by author.
Last edit: 03:25, 20 March 2020

Blaise, you are correct that sentence should be modified. In soils with high clay and high OM at HIGH pH - CEC will be high (which also means AEC will be low). The answers posted on the wiki have been modified and reposted.

SandraBrown (talk)03:01, 20 March 2020

Thank you for the clarification!

BlaiseMatlock (talk)03:02, 20 March 2020