Certified Crop Advisor Practice Exam

What happens to the concentration of hydrogen ions in the soil as the pH level decreases?

1. It decreases

2. It increases

3. It stabilizes

4. It varies

The correct answer is: It increases

As the pH level in the soil decreases, the concentration of hydrogen ions increases. pH is a measure of the acidity or alkalinity of a solution, with lower pH values indicating higher acidity. When the pH drops, it reflects a higher concentration of free hydrogen ions (H+) present in the soil solution. This is because pH is defined as the negative logarithm of the hydrogen ion concentration. Therefore, as pH decreases—indicating a more acidic environment—the corresponding concentration of hydrogen ions inherently rises, leading to the conclusion that as pH decreases, hydrogen ion concentration increases. This fundamental concept is essential in soil chemistry and has significant implications for nutrient availability, soil microbial activity, and overall soil health.