Certified Professional Horticulturist (CPH) Practice Exam

Soil is made up of organic matter, inorganic matter, air, water, and...

1. Broken down rock

2. Microorganisms

3. Decaying plants

4. Minerals

The correct answer is: Microorganisms

Soil consists of several key components that contribute to its overall health and fertility, and microorganisms play a crucial role in this ecosystem. These tiny organisms, including bacteria, fungi, protozoa, and nematodes, are essential for decomposing organic matter, thereby releasing nutrients that plants need for growth. They help in enhancing soil structure, improving aeration, and aiding in water retention. Furthermore, microorganisms are involved in biogeochemical cycles, such as the nitrogen cycle, which is vital for converting nitrogen into forms that plants can utilize. Their presence increases soil biodiversity, which contributes to soil resilience and health. While other constituents like broken down rock, decaying plants, and minerals all play roles in soil composition, it is the microorganisms that actively foster nutrient cycling and soil vitality, highlighting their unique and indispensable contribution to soil ecology.