Certified Professional Horticulturist (CPH) Practice Exam

What is the main purpose of maintaining a proper pH level in the soil?

1. To reduce soil temperature

2. To enhance nutrient availability

3. To improve soil texture

4. To prevent pests

The correct answer is: To enhance nutrient availability

Maintaining a proper pH level in the soil is crucial for enhancing nutrient availability. Soil pH significantly influences the chemical forms of nutrients and their availability to plants. When the pH is within the optimal range—typically around 6 to 7 for most crops—essential nutrients like nitrogen, phosphorus, and potassium are more soluble and accessible for plant uptake. Conversely, if the pH is too low (acidic) or too high (alkaline), certain nutrients may become less available or even toxic, leading to deficiencies that can hinder plant growth and productivity. For example, in highly acidic soils, nutrients such as calcium and magnesium can become limited, while aluminum can become soluble and toxic to plants. On the other hand, alkaline soils can limit availability of micronutrients like iron, zinc, and manganese. Therefore, managing soil pH is essential for ensuring that plants receive the necessary nutrients to thrive. The other options, while important aspects of soil and plant health, do not play as direct a role in the accessibility of nutrients as pH does. Soil temperature, texture, and pest prevention are affected by a variety of factors, but nutrient availability remains the primary concern regarding soil pH.