There are several possible causes for a compost pile being too wet. Choose the most likely cause and address that.
If the pile remains wet, choose the next most likely cause and follow instructions for addressing that. Keep trying the solution for the next most likely cause until you solve the problem.
Too Much Water Added When Building the Pile
Solution: Re-stack pile, adding dry carbons. Next time you build a pile, water every 4 – 6” layer, but with less water than before.
This is an unusual problem for new composters, but possible. If you are using fresh manure, it may have already had enough moisture in it. Just chalk it up to a learning experience. Re-stack the pile adding dry carbons, and use a little less water next time
Pile Built On a Spot with Poor Drainage
Solution: Find a new location for your compost pile. Re-stack pile in that location, adding more dry carbon materials to each layer.
Sometimes people think they will solve two problems at once by building a compost pile on a spot with poor drainage. They think the pile will absorb the excess water while freeing them from watering the pile.
But here’s what happens: The pile becomes waterlogged with stagnant water. No air can get to the bottom of the pile so aerobic bacteria (bacteria who need air) can’t live there and the anaerobic bacteria (bacteria who can live without air) move in. The anaerobic bacteria stink very badly. Which is probably how you happen to know the pile was too wet, isn’t it? So find a new location with good drainage and restack your pile there, adding dry carbons as you go.
Composting during Rain or Snow
Solution: Re-stack pile, adding dry carbons. If you have more nitrogen materials, you can add them too. Then cover the pile.
The best way to maintain the proper moisture level during periods of high rain or snow is to cover the pile. Some compost bins come with covers. Covers can be purchased separately.
The pile will still have moisture even though the rain is prevented from entering. As moisture from the pile evaporates, it condenses on the cover and falls back into the pile.
When using a cover, the “sweet spot” center of the pile may extend all the way to the top of the pile since the cover is retaining heat and moisture. This is great for your compost, but it means that when you take the cover off, there will be lots of decomposers right there on the top of the pile. Remove the cover with care. This warning is probably less worrisome in cold snowy weather than in rainy weather.
I lay an old shower curtain or other sheet of plastic over the top of the bin and weigh it down with bricks or stones. There has been some concern over the disintegration of plastic products getting into the compost, so it would be more organically-correct to use a sheet of aluminum instead.
The good thing about a sheet of aluminum is that you can set it at an angel so the water and snow runoff can purposefully be directed somewhere more useful, like a rain barrel. When you set it up, remember that the water condensing on the underside may run off too, so some of that will need to be directed back into the pile.
Mary Tynes, Master Composter, www.mastercomposter.com
Image Credit (top left): http://www.flickr.com/photos/joi/534318829/
Image (bottom right): Pyramid Composter