Red Seal Landscape Horticulturist Practice Exam

Why is soil pH an important factor in gardening?

1. It determines soil temperature

2. It affects nutrient availability and microbial activity

3. It controls weed growth

4. It regulates moisture levels

The correct answer is: It affects nutrient availability and microbial activity

Soil pH is a crucial factor in gardening primarily because it affects nutrient availability and microbial activity. Plants require various nutrients to grow, and the pH level of the soil influences how readily these nutrients can be absorbed by plants. Most nutrients are available to plants within a pH range of 6.0 to 7.5. Outside of this range, certain nutrients may become less available; for example, at lower pH levels (more acidic), nutrients like phosphorus can become locked up in the soil and unavailable to plants. Conversely, at higher pH levels (more alkaline), nutrients such as iron may become deficient, leading to issues like chlorosis in plants. Additionally, soil pH impacts microbial activity, which is vital for the decomposition of organic matter and nutrient cycling. A balanced pH supports a healthy microbial community that helps break down organic materials into forms that plants can use. This interaction between soil pH, nutrient availability, and microbial processes is integral for establishing a healthy garden environment, promoting robust plant growth, and maximizing yield.