Certified Arborist Practice Exam

Which two elements are the most important to measure in a soil sample?

1. Nitrogen, phosphorus, and potassium

2. Defense and pH

3. Micronutrients

4. Hardiness and bark texture

The correct answer is: Nitrogen, phosphorus, and potassium

The most important elements to measure in a soil sample for supporting plant health and growth are nitrogen, phosphorus, and potassium. These three nutrients are commonly referred to as the primary macronutrients, vital for various physiological processes within plants. Nitrogen is essential for the production of chlorophyll and amino acids, phosphorus plays a critical role in energy transfer and root development, and potassium aids in water regulation and enzyme activation. While micronutrients are also important for plant growth, they are required in much smaller quantities than macronutrients. Soil pH is significant as well since it affects nutrient availability, but it is not an element in itself. Defense mechanisms and bark texture are more related to the characteristics of trees rather than soil composition and nutrient levels. Therefore, focusing on nitrogen, phosphorus, and potassium provides a better understanding of the soil's capacity to support healthy plant growth.