Certified Professional Horticulturist (CPH) Practice Exam

Why is soil pH important for plant health?

1. Certain soil-borne diseases

2. Microbial activity

3. The availability of nutrients

4. Seed germination rates

The correct answer is: The availability of nutrients

Soil pH is critically important for plant health because it directly affects the availability of nutrients within the soil. Different plants have varying pH preferences, and the solubility of key nutrients can change significantly with pH fluctuations. Many essential nutrients, such as nitrogen, phosphorus, potassium, calcium, and magnesium, are most accessible to plants within a specific pH range, typically between 6.0 and 7.5 for most crops. If the pH is too low (acidic) or too high (alkaline), certain nutrients may become less available, which can lead to nutrient deficiencies and adversely affect plant growth, development, and overall health. For instance, iron availability decreases in alkaline soils, which can lead to chlorosis in plants. Maintaining an optimal soil pH is therefore essential for maximizing nutrient uptake and supporting healthy plant development. This is why understanding and managing soil pH is a key aspect of horticultural practices.