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Managing Moisture In Compost

Compost PileThe record drought locked on many (and we mean many) parts of the country calls for home gardeners as well as commercial interests to rethink their watering strategies. Equally important to organic gardeners is the moisture content of their composting pile.

Moisture in compost is critical and having too much or too little can slow or sour the process. Having too little will slow or stop the composting process. Having too much moisture in the pile will fill the necessary air spaces and turn the process into an anaerobic digester something most garden composters want to avoid (though it is an accepted composting technique with its own set of requirements).

With the right equipment, turning garbage into garden gold is a cinch! At Planet Natural we supply everything you need: bins, tumblers and activators to get your pile cooking, plus compost turners to aerate your heap. Now, let’s rot!

How do you know if your compost pile needs watering? Most expert composters suggest a moisture content of 40% to 60%. A quick, hands-on visual check should tell you if the pile is too dry: it will lack heat and there’ll be little evidence of organic material break down. If you compost is too wet, it’s probably slimy and smells bad. A good rule-of-thumb is the sponge test: your compost should have the consistency and moisture content of a wrung-out sponge when you squeeze it. Compost moisture meters are available but are more useful to commercial composters. They’re not really necessary for the home composter who can tell by feel how their pile is doing (they also require multiple readings — one part of your pile may be damper than others — and tend to be expensive).

Solutions? Easy… If your compost is too dry, water it from the top down until you reach the desired “wrung sponge” consistency. A good turning at this point will aid in even distribution of moisture. If your compost it too wet, try adding newspaper paper, brown (unbleached) cardboard or chopped straw (make sure it’s seed free if you can). The idea is to open up your pile’s insides so that more air may circulate through. Adding air by turning your pile can also help (but is a lot more work). The best time to get you pile’s moisture content just right is when you build it. Once a pile is started properly it’s almost self-maintaining (minus that turning). There’s also the chance that if you live in a wet coastal climate your pile will be too wet because of frequent rains. Covering your pile with straw or even a tarp will help. And it will help contain heat.

One of the best ways to maintain your compost’s moisture content is to process it in a compost bin or tumbler. Not only will it help your compost retain moisture that might be lost through evaporation, it makes turning — the introduction of air — easy. And if you happen to live in a place where rain is abundant, it will keep moisture from you compost. This summer, few of us can imagine that kind of problem.

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7 Responses to “Managing Moisture In Compost”

  1. Evo on August 14th, 2012 at 10:44 pm #

    We are beignning a program in our middle school where we will be training our students to separate lunch waste in order to compost the organic leftovers. If anyone out there has tried this at their school or has any advice (about implementation, not composting), please send it my way.> We have instituted this program in two of our branch schools, both with great success. The two things that were key: (1) getting the kids to understand that NO MEAT of any form goes into the compost/pig food (we used the sludge for both). We shortly resorted to huge signs explaining why this wasn’t smart. (2) We had to make sure there was a person assigned to keep an eye on the bucket and haul it out regularly so that it didn’t overflow, and encourages folks to dump organics in the other garbage. Terri Watson – Lander, Wyoming

    • PTSA at SAS on August 4th, 2013 at 6:24 pm #

      My daughters’ school composts. Everyone is on board. No classroom is required to compost, but most classrooms do. A bucket is kept each the classroom and a child is assigned to “compost duty” where he or she dumps it daily. There is a gardening program at the school. The pile is maintained by the children in their weekly gardening class. It is a simple system, just a wire cage set up away from the school buildings. Good luck!
      Tallahassee, FL

      • Debra on July 6th, 2016 at 12:45 pm #

        I would love to start a similar program at my kids school. Would you mind sharing how you started the gardening and compost program with me? Also, what grade did you start the program for…elementary or middle?
        Thank you,

    • Debra on July 6th, 2016 at 12:41 pm #

      Hi Terri,
      What a great idea! I would love to start a similar program at my kids school. Would you mind sharing how you started, and now run the school program with me? I would greatly appreciate it.
      Thank you,

  2. S Miller on August 22nd, 2013 at 4:09 am #

    Some neighbors gave me six large plastic bags of lawn clippings. Procrastinating, I let the bags sit for a month & half until they started stinking, so I moved them to my compost bin. Saw that the flies, spiders & other bugs had set up shop in the wet grass. I mixed in some dirt, wood chips/shavings in with them. How long will the smell last, & is there something else I need to add? Also I am expecting rain tonite, so should I cover the bin in order for the grass to dry out? I’m trying to avoid public nuisance fines & keep peace with the neighbors. I am welcome to any helpful suggestions….

    • E. Vinje on August 22nd, 2013 at 5:53 am #

      S Miller –

      Make sure to include a mixture of brown fibrous ingredients with your greens. A well-balanced “diet” will ensure that composting doesn’t take too long and that you don’t end up with a slimy, smelly heap. Also, aerate the pile often to provide oxygen for the composting microbes. When a pile goes anaerobic it starts to smell. Here’s a couple links:


  3. John Chapman on June 9th, 2018 at 2:38 am #

    I live in New Mexico where the average humidity stands around 16 to 19 %. As such keeping moisture in the compost pile is at best difficult. I believe a moisture barrier that allows air circulation and prevents moisture passage should solve the problem, however the barrier should have at least a year before UV light breaks the material down. Please help me find the best product that fits my needs.

    Thank you for your time spent on this question.

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