What is the most appropriate method of averaging the pH of soil horizons? A straight weighted average of the horizons, such as 10 cm of a pH 4.5 soil averaged with 10 cm of pH 6, would be 5.25. But there are some who suggest that pH should be exponentially transformed with the rationale that pH is really hydrogen concentrations. However, this seems to skew the distribution towards acidity. Doing it this way would result in an effective pH of 4.79. Doesn’t the hydroxide concentrations count as well? Why wouldn’t it skew towards alkalinity? It seems to me that pH is already transformed appropriately, because acidity and alkalinity are not independent of each other; one goes up while the other goes down.
A practical test would be to measure the pH before, and after contrasting pairs of soil samples are physically mixed. I am sure someone out there has tried it. It certainly happens in the field when someone plows a soil. I expect the results would also depend on the buffering capacity of the respective horizons involved. If it was acidic sand with a low cation exchange capacity mixed with a calcareous loam with high cation exchange capacity, the pH after mixing equal parts would be closer to the pH of the original clay sample. On the other hand, if there is an acidic clay with a high cation exchange capacity or a muck acidic due to organic acids, I would expect the acidic component of the mixture would have a more equal role in buffering the mixture.
