How do I identify high-quality finished compost?
Written by
Liu Xiaohui
Reviewed by
Prof. Martin Thorne, Ph.D.Recognizing high-quality compost is essential if your garden is to receive its full benefits. Good compost is a rich, chocolate-brown color, similar to rich chocolate soil. Its texture crumbles easily with pressure. You will notice a pleasant earthy smell with no sour or ammonia smell. There are no visible bits of food or chunks of mess in the finished product.
Visual Characteristics
- Dark brown to black coloration indicates complete decomposition
- Uniform crumbly texture without sticks or recognizable materials
- Absence of mold or fungal growth on surface
Olfactory Tests
- Earthy forest aroma signals proper aerobic decomposition
- No ammonia smells meaning balanced nitrogen content
- Lack of sourness confirming correct pH levels
Physical Tests
- Cool temperature below 100°F showing stable biology
- Moisture balance releasing 1-2 drops when squeezed
- Screening results passing through 0.5 inch mesh easily
There are straightforward tests you can do at home to evaluate the quality of your compost. Use the squeeze test to check the moisture content. The quality of the compost is such that it forms a loose ball that breaks apart easily. A quality compost will not be too wet or give off a dusty feel. Use a compost thermometer to check that the temperatures are down, confirming that the biological activity has stabilized in your compost. I perform these tests on new batches of compost at the start of each new season.
Learn why these indicators are scientifically important. The color black comes from stable humic acids, which nourish plants. The crumbly texture allows for good root penetration and water movement. The low temperatures suggest that pathogens have been killed by hot composting. The earthy smells indicate that beneficial microbes dominate in the mix.
Avoid making common errors in compost evaluation. Greenish hues indicate unfinished decomposition. Slimy consistencies indicate anaerobic conditions. Heat in excess of 100° is indicative of continuing biological reactions. Pieces of wood or eggshells indicate that the compost has not yet been properly processed. Such a compost, then, requires additional curing before it can be used.
Improve your bad compost with simple remedial action. Screen out the lumps to ensure a uniformly textured product. If there is an odor, turn the pile to reintroduce oxygen. Add dry browns to remedy excessive moisture. Allow an additional 2-4 weeks for the compost to cure, allowing the temperature to stabilize. Quality compost can reduce entire gardens within a matter of weeks.
Read the full article: Choosing the Best Compost for Gardens
