Certified Professional Horticulturist (CPH) Practice Exam

What is a key factor in the availability of nutrients in soil?

1. Sunlight exposure

2. Soil moisture levels

3. Soil pH

4. Organic matter content

The correct answer is: Soil pH

Soil pH is a critical factor in the availability of nutrients in soil. The pH level determines how well plants can absorb essential nutrients from the soil. Different nutrients have varying solubility at different pH levels, which means they become available to plants within a certain pH range. For instance, many micronutrients become more soluble and available to plants in slightly acidic conditions, while others could become less available as the soil approaches more alkaline conditions. Additionally, soil pH influences microbial activity in the soil, which plays a significant role in nutrient cycling. An appropriate pH level fosters the right environment for beneficial microorganisms to function effectively, further contributing to nutrient availability. While other factors like soil moisture levels and organic matter content can impact nutrient availability as well, they mostly serve to facilitate the delivery and retention of nutrients rather than directly influencing how these nutrients interact chemically within the soil environment. Sunlight exposure is primarily important for photosynthesis, rather than directly impacting nutrient availability in the soil.