Certified Professional Horticulturist (CPH) Practice Exam

If the Carbon to Nitrogen Ratio of a compost pile is currently 10/1, what should you add to balance it?

1. Add vegetable plant debris

2. Add some eggshells

3. Add some dry leaves or prunings

4. Add fresh grass clippings

The correct answer is: Add some dry leaves or prunings

To balance the carbon to nitrogen ratio in a compost pile that has a ratio of 10:1, it is essential to add materials that are high in carbon since the current ratio is already leaning towards a nitrogen-rich state. Dry leaves or prunings, which are carbon-rich materials, are a good choice for this purpose. These materials typically have a higher carbon content compared to nitrogen, which can help to bring the overall carbon to nitrogen ratio closer to the ideal range of approximately 30:1. Adding dry leaves or prunings will contribute the necessary carbon to help balance the compost pile, facilitating proper microbial activity during the decomposition process. In contrast, the other options, such as vegetable plant debris, eggshells, and fresh grass clippings, are generally higher in nitrogen content. Adding these materials would further lower the carbon to nitrogen ratio, exacerbating the imbalance instead of fixing it. For effective composting, it's crucial to maintain the proper ratio to promote optimal decomposition and to avoid issues such as odors or slow composting.