Certified Professional Horticulturist (CPH) Practice Exam

A properly functioning compost pile should be how many degrees?

1. 110 F

2. 120 F

3. 130 F

4. 140 F

The correct answer is: 140 F

A properly functioning compost pile should ideally reach temperatures between 130°F and 160°F (about 54°C to 71°C). This range is essential for effective microbial activity that breaks down organic matter and helps to eliminate pathogens and weed seeds. Reaching around 140°F indicates that the compost pile is in a thermophilic phase, where heat-loving microorganisms thrive. These temperatures provide a favorable environment for bacteria that accelerate the decomposition process. Maintaining these temperatures is crucial because they help to ensure that volatile compounds are broken down and that the organic material is decomposed efficiently. While 110°F, 120°F, and 130°F may reflect some level of microbial activity, they are generally considered too low to ensure optimal decomposition and pathogen eradication. Therefore, 140°F is the minimum threshold that indicates a compost pile is functioning effectively and is sufficiently active in the thermophilic phase.