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Compost bin floor in contact with soil

Posted by Alico268 7 (My Page) on
Wed, Mar 19, 14 at 9:46

Good morning Gardeners,

I checked the FAQ and searched this forum but was not able to find an answer to my question.

I am going to construct a 3 bin compost system, and from looking at designs on the internet, I noticed that some had floors separating the compost from the soil and others did not letting the soil come in contact with the compost. Personally, I would think that I would want soil contact for benefit of creepy crawlies having greater access to the compost. Perhaps I'm missing something? Is a hot pile too much heat for worms and such?

Just thought I would get a little more advice before settling on a design to construct. I am a novice gardener who has a 250 square foot garden bed and 6,000 sq. ft. lawn. I compost leaves, weeds, kitchen greens, garden plants and lawn clippings occasionally. The compost benefits the garden, lawn and beds.

Also, if using cedar or redwood for the wood material on the compost bin, is there a safe stain/protectant one can use?

Any advice or perspective would be greatly appreciated. Thank you to all that make this such a wonderful site!

Follow-Up Postings:

RE: Compost bin floor in contact with soil

  • Posted by ericwi Dane County WI (My Page) on
    Wed, Mar 19, 14 at 10:25

I suggest that you think of your wooden compost bin as a consumable, sort of like the tires on your car. It will last a few years, and eventually become compost. Our compost is on the ground. I am sure that some of the nutrients end up in the ground, under the pile. On the other hand, the pile is self-draining, so it is never too soggy. If you compost in a bin or container that does not drain, you will have to manage moisture. It might help to have dry sawdust available.

RE: Compost bin floor in contact with soil

It is not necessary for a compost bin to have ground contact. Many commercial composters do not and some people purposely build a bin that is raised above the ground and harvest the finished compost from under the bins rather than dig in the bin. The material you put in for digestion already has what is needed to be digested, all you do is make conditions optimal for faster digestion. For most of us it is simply easier to build the bins with ground contact.
When using cedar or redwood (cedar is a better choice if only because of sustainability) there is no need for a sealer or protectant.

RE: Compost bin floor in contact with soil

It may not be necessary for a compost bin to have ground contact, but it is a very good idea for two reasons:

1) makes it easy for worms to move in and out of the pile. They move in when the temp drops; so it is good for cold and hot composting. The hot compost phase does not last forever.

2) the compost pile does not have to be as high when the pile rests on the ground. Lets take a 4' by 4' pile as a example. If you have the bin off the ground, say by putting thick woody branches at the bottom, the pile will have to be 4' high for max heat retention. If your compost pile sits on the ground, the compost pile can be less than 4' high. Because the dirt acts to store heat.

My two piles are 4'by8' by 24" to 30" high. I can reach 150F core temp with this size pile.

So which height pile would you rather turn over or move -- 48" high, or 24 to 30" high?

This optimal pile size is for hot compost piles. But I suggest that it might be a good idea to size your bins such that you COULD make hot compost if you wish. Nothing forces you to do so.

Cold composters don't have to worry about pile size.

I notice that folks hardly ever say what they will compost. That might be important.

Suggestions for bin sizes for ingredients:
Leaves finely shredded and some sawdust 3'by3' or 3' round.
Leaves finely shredded 4'by4' or 4' round
Wood Chips 5'by5' or 5' round

RE: Compost bin floor in contact with soil

Keep in mind that a optimal or larger size pile will not CAUSE a hot compost pile core temp.

Rather, it will RETAIN the the heat that a good mix/moisture range/particle size compost pile starts with. And when in the hot stage, those thermophilic bacteria really go to town and reproduce at a astonishing rate.

RE: Compost bin floor in contact with soil

Earthworms are not a significant part of making compost since in a properly built compost pile the moisture level is too low for them to survive. A compost pile with enough moisture for earthworms to live in will not be conducive for the bacteria to work and generate the heat that indicates they are busy working.
That is why tumbler composters sometimes do work.

RE: Compost bin floor in contact with soil

"This is when the third stage of composting, the cooling phase, takes place. During this phase, the microorganisms that were chased away by the thermophiles migrate back into the compost and get back to work digesting the more resistant organic materials. Fungi and macroorganisms such as earthworms and sowbugs that break the coarser elements down into humus also move back in." "The Four Stages of Compost"

Also, I fish. When the ground is dry it is easier to look for worms in the compost pile.

RE: Compost bin floor in contact with soil

Below is a link to the bin system I created last Autumn. It has a lot of good info in it. If you search by my username you'll find other threads (with pics) related to the progress of my system as I constructed it.

It's made of untreated pine and covered in tung oil for some protection from the elements. Once it falls apart my plan is to replace it with a cedar version.

It was cooking up my compost pretty nicely until we got hit with a wicked cold winter here in the Northeast. Once it became impossible to turn the compost (which I always did to cover up my kitchen scraps from vermins) all I could do was dump coffee grinds on top of it for the rest of the winter.

I was finally able to turn the compost today but it did have some pretty large chunks of frozen "compost" that need to thaw out so I made sure I laid them on top of the loose stuff.

Here is a link that might be useful: 3-bin system

RE: Compost bin floor in contact with soil

Earthworms may well move into finished compost and begin to eat that material, but I would prefer they do that in the garden where my plants would benefit more.
For the purpose of converting vegetative waste into finished compost earthworms are not a significant means of doing that, except in a vermicomposting operation.

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