Hi @Colinhendee

This is a great thread.

We do still use ammonium acetate extraction to evaluate calcium and magnesium balance on the soil colloid.

” I *think* I understand that AA and M3 show a fairly linear correlation, meaning I can base classical Albrecht balancing on the AA analysis with the right adjustment. (Open to correction on that.)”

We find this to be generally correct.

One key aspect that is often missed on sandy soils, calcium should be a minimum of 1000 ppm, regardless of CEC, to produce healthy crops.

Also, gypsum doesn’t seem to do a great job of building soil calcium levels. Calcium carbonate is much more effective, and is preferred unless the soil bicarbonate levels are quite high.

@Stephen_Sinnott @Smaricle @BrianDougherty