What does pH measure in soil?

• A. The hydrogen ion content in soil mixed with water, indicating acidity or alkalinity.
• B. Soil moisture content.
• C. Total organic carbon.
• D. Salt concentration.

Answer: (A)

pH is a measure of how acidic or basic (alkaline) the soil is, based on the hydrogen ion activity in a soil–water mixture. In soil science, the important thing is the concentration of hydrogen ions in the soil solution, because it drives how nutrients behave and how microbes function. When there are more hydrogen ions, the solution is more acidic; with fewer hydrogen ions, it’s more basic.

A soil sample is combined with water (often distilled) to create a soil–water suspension, and the pH is read with a pH meter or color indicator. This value tells you where the soil falls on the acidity–alkalinity spectrum, which in turn guides liming or sulfur amendments to optimize nutrient availability.

So, pH measures the hydrogen ion content in soil mixed with water, indicating acidity or alkalinity. It is not a measure of soil moisture, organic carbon, or salt concentration.