Red Seal Landscape Horticulturist Practice Exam

How does pH affect soil and plant health?

1. It influences nutrient availability and microbial activity in the soil

2. It determines the color of the soil

3. It affects the soil texture

4. It controls water retention in soil

The correct answer is: It influences nutrient availability and microbial activity in the soil

pH plays a crucial role in soil and plant health by influencing nutrient availability and microbial activity in the soil. The pH scale measures how acidic or basic a soil is, and this acidity or alkalinity can significantly affect the solubility of nutrients. Certain nutrients are more available to plants at specific pH levels. For instance, essential nutrients like nitrogen, phosphorus, and potassium tend to be more available in mildly acidic to neutral soils (pH 6-7), while others, such as iron and manganese, may become less available in alkaline conditions. Additionally, soil pH impacts the microbial community in the soil, which is beneficial for plant health. Most soil microorganisms thrive in a specific pH range, and their activity is important for processes such as decomposition and nutrient cycling. An imbalance in pH can lead to reduced microbial activity, affecting the overall health of the soil ecosystem and consequently, plant health. The other choices do not accurately convey the primary influence of pH on soil and plant health. While pH may have secondary effects on soil color (such as iron oxides affecting hues in highly acidic soils) or interact with certain aspects of soil texture and water retention, these factors are not the primary relationships influenced by pH.