Acidity or Moisture?

I'm a little confused on something. When we refer to "acidity" in soils, are we referring to the pH balance of the water contained in the soil or are we referring to the abundance of "moisture" within the soil. I've heard ppl say that you can interchange a moisture meter with a pH meter bc they essentially give the same reading. Can anyone weigh in on this?


thanks


mt

We are referring to the pH of the water contained in the soil.

However, things gets a little bit complicated when you try to analyze and understand details.

First of all, pH depends on the acid concentration (technically it is -log of H+ activity, but I am not going to discuss every detail, fat books have been written on the subject). Dependence is not a simple one, but it exists. Soil contains acids and water. BUT - depending on the amount of water in the soil (soil moisture) acid concentration will vary to some extent, so pH of the soil is moisture dependent. Differences are not large (due to the so called buffering effect of weak acids) but nonetheless they exist.

Second - pH of soil can be highly dependent on the way it is measured. Simple pH meters (these without batteries, that you just stick into soil) tend to change their indications depending on the soil moisture level. Correct procedure calls for mixing soil with water, waiting, and measuring pH of the supernatant liquid. See my page (pH meter) for details. As the measurement results can vary, it is hard to tell what the REAL soil pH is. However, as long as we all stick to the same procedure, we can compare pH measurements results and decide, whether soil is too acidic or too basic.

HTH