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Grittyville, WA

https://www.researchgate.net/post/What-about-Anion-Exchange-Capacity-when-managing-studying-soil-fertility

I thought this reply was the best:

"Good question. Most of the soils are negatively charged, and therefore CEC is important for soil fertility management. However, Not all soil surfaces are negatively charged. For example, in volcanic soil, Fe and Al hydroxides/oxides form at the surface of clay minerals. These Fe/Al oxides positively charged and specifically adsorb negatively charged anions. Allophanic soils suffer P deficiency due to high AEC (or Anion Specificities Capacity or P retention), it is a major research area in literature especially for allophanic/andisols. While PO4- is strongly adsorbed, SO4- is lesser extent in specifically adsorption, and NO3- is not adsorbed at all, easily leached from soils."

3/10/2026 3:27:16 PM