Certified Professional Horticulturist (CPH) Practice Exam

Compost is ready when:

1. The pile is dark brown

2. The components are unrecognizable, and the temperature of the compost and the air are similar

3. The pile has an earthy, non-offensive odor and releases small amounts of steam when turned

4. The components have reduced to ½ inch, and they feel slightly moist

The correct answer is: The components are unrecognizable, and the temperature of the compost and the air are similar

Compost is considered ready when the components have decomposed to the point that they are unrecognizable, indicating a significant breakdown of organic materials, and when the temperature of the compost pile has stabilized and is similar to that of the surrounding air. This stabilization in temperature is a key sign, as the active decomposition process generates heat; once the pile cools, it typically means that the microbial activity has slowed down, and the material is nearing completion. While factors like color and odor are important in assessing compost quality, the defining characteristics that signal it is ready for use are the breakdown of materials and the adjustment of temperature to that of the environment. The other criteria involving smell or particle size can be supportive observations but are not definitive indicators on their own. Therefore, the unrecognizability of components and the stabilization of temperature are strong indicators that the composting process has completed sufficiently for the material to be considered ready for application.