Compost should be moist, not dry. It needs moisture for the microorganisms that break down organic materials to thrive and do their work effectively.
Why Moisture Matters in Composting
Decomposition in a compost pile is primarily driven by microbial activity. These tiny organisms require water to survive and digest the organic matter you add. If the compost material becomes too dry, microbial activity slows down significantly or stops altogether, halting the composting process.
Recommended Moisture Levels for Composting
Maintaining the correct moisture level is crucial for efficient composting. The ideal state is often described as being like a wrung-out sponge – damp, but not soaking wet.
Based on best practices:
- To support a hot compost process, a minimum moisture content of 50% is recommended.
- Hot compost piles are dynamic environments and can lose moisture quickly, potentially losing 1% of moisture content every day, especially in warmer conditions.
- Therefore, in warm climates, a starting moisture content of 60% is recommended for a blended compost recipe to account for daily moisture loss.
These percentages ensure there is enough water for microbial life without creating anaerobic (oxygen-deprived) conditions.
Checking Your Compost Moisture
The easiest way to check if your compost pile has the right amount of moisture is the squeeze test:
- Grab a handful of material from the center of your compost pile.
- Squeeze it firmly.
- Optimal Moisture: A few drops of water should trickle out, and the material should hold its shape when you open your hand.
- Too Dry: The material crumbles apart, and no water comes out when squeezed.
- Too Wet: Water streams out easily when squeezed, and the material feels soggy and heavy.
What Happens if Compost is Too Dry?
- Decomposition slows down or stops completely.
- The pile won't heat up properly in a hot composting system.
- It takes much longer for the materials to break down.
What Happens if Compost is Too Wet?
- Water fills the air pockets, displacing oxygen.
- The pile becomes anaerobic, leading to foul odors (like rotten eggs).
- Beneficial aerobic microbes are inhibited, and decomposition becomes inefficient.
- Nutrients can leach out of the pile.
In summary, for effective composting, your pile needs to be consistently moist, maintaining levels typically between 50% and 60%, depending on the process and climate.
