Certified Professional Horticulturist (CPH) Practice Exam

What is the most effective and longest lasting source of organic matter?

1. Compost

2. Grass clippings

3. Manure

4. Straw

The correct answer is: Compost

Compost is considered the most effective and longest lasting source of organic matter due to its comprehensive nutrient profile and stability. When organic materials such as kitchen scraps, yard waste, and other biodegradable substances undergo the composting process, they decompose and transform into a rich, dark material. This organic matter is not only high in essential nutrients for plant growth, but it also enhances soil structure, improves moisture retention, and promotes beneficial microbial activity within the soil. Unlike grass clippings, which break down relatively quickly and may require more frequent application, compost offers a longer-lasting benefit because it is well-decomposed and can improve soil over time. Similarly, manure can vary in its effectiveness based on its source and treatment, and while it adds nutrients, it may not provide as much lasting organic matter as fully matured compost. Straw, while helpful as a mulch, decomposes faster and does not contribute to soil structure to the same degree as compost does. Overall, compost stands out for its ability to enrich the soil steadily, making it an essential component for sustainable horticulture practices.