Certified Crop Advisor Practice Exam

As soil pH decreases, what happens to hydrogen ion concentration?

1. It increases

2. It decreases

3. It remains the same

4. It fluctuates

The correct answer is: It increases

When soil pH decreases, it indicates a more acidic environment. The pH scale typically ranges from 0 to 14, with lower values representing higher acidity. pH is a logarithmic measure of the hydrogen ion concentration in a solution, meaning that each unit change in pH represents a tenfold change in hydrogen ion concentration. As the pH value goes down, this signifies an increase in hydrogen ions in the soil solution. For example, a pH of 6 is ten times more alkaline than a pH of 5, which means there is a much higher concentration of hydrogen ions at pH 5 compared to pH 6. Therefore, when the soil pH decreases, it is accurate to state that the concentration of hydrogen ions in the soil increases. This relationship is crucial for understanding soil chemistry, plant nutrient availability, and overall soil health, as higher hydrogen ion concentrations can affect nutrient solubility and biological activity in the soil.