How often do you water compost?

QUESTION: How often do you water compost? Blake C

ANSWER: Maintaining the moisture level of your compost at the right point is vital for keeping your compost healthy, as the appropriate amount of moisture supports health and performance of the microbes that help with decomposition and helps control the temperature of your compost.

Too much water in the compost can choke out the available oxygen, leading to anaerobic conditions and slowing down the microbes that break down your compost materials until they’re working at a creep. Too little water can lead to slow decomposition, uneven temperature, and even spontaneous combustion.

Unfortunately, there isn’t a rule that’s set in stone to tell you how frequently your compost will need to be watered because there are so many variables at play. The size of your compost bin will affect how frequently water needs to be added, as will your climate, the materials you are composting, and many other factors. 

What you need to know is this: Your compost should have the moisture level of a sponge that has been wrung out. If it’s drier than a wrung-out sponge, add some water. If it’s more moist than a wrung-out sponge, you’ll need to take steps to balance out the extra moisture. In other words, your compost should be made up of 40 to 60 percent water. 

(If the wrung-out sponge guideline doesn’t click for you, there’s another way to test your compost’s moisture level. Take a handful of dried leaves from your compost—this test only works with dried leaves—and squeeze them in your fist. The moisture level is right when only one or two drops trickle out of the dried leaves when you squeeze them.) Take a few moments to check the moisture level of your compost whenever you’re turning and mixing the compost pile (every few weeks, that is). 

If your compost is too dry, just use your garden hose to sprinkle water into the compost for a few minutes. Alternatively, for a more hands-off approach, if you water your compost the same day as you water your lawn, you can set up your yard sprinklers so that some of the water sprays into your compost bin. You can also counteract dryness by mixing in more wet nitrogen-rich “green” ingredients, such as coffee grounds, freshly trimmed grass, or scraps of fruit and vegetables.

If your compost gets too much hydration and you need to dry it out some, the first thing you should do is prop open the lid of the container, as long as it’s a warm, sunny day. Make sure that if a rain shower begins while your compost is drying out, you close the lid of the bin, or you’ll defeat the purpose and get the compost even more wet. If a day or two of sun doesn’t dry things out well enough, you have the option of removing the compost from the bin and spreading it out in a thin layer to dry off, then replacing it in its container.

Another way to counteract an overly wet compost pile is to balance the wetness out with dry ingredients. Mix in plenty of dry, carbon-rich “brown” materials such as dried leaves, dried grass clippings, shredded newspaper, or shredded cardboard.