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I watched this timelapse of litter decomposition. This makes me wonder if turning the compost actually slow down composting by discouraging detritivores and burrowers to live in the compost. I would imagine turning the compost frequently makes it a less ideal place for most of these organisms (so the frequency is important) which seem to be efficient at reducing the particle size of litter (fallen leaves are usually the bulk ingredient of the compost) as in the video.

Does turning over a compost pile slow down its decomposition?

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I sort of agree with both the answers you've been given, but essentially, no, turning the compost pile does not slow down decomposition over time.

It is perceived wisdom that turning a compost heap regularly will mean that the resulting compost is ready much quicker, and will be suitable for use in potting soil mixes because the heat generated in a turned heap means weed seeds and pathogens will have been destroyed. Climate where you are makes a difference - in hotter places, turning the heap may be essential to cool it down temporarily, but in temperate regions, its unlikely the average compost heap will get hot enough to destroy pathogens, and will take longer to turn into compost,see here for the standard advice http://www.homecompostingmadeeasy.com/turningcompost.html. Basically, the choice is between a faster hot, aerobic heap (turned regularly) or a slower cold, anaerobic one (not turned).

Your very interesting time lapsed video link shows a leaf litter layer rather than an actual compost pile comprised of different materials, and all it demonstrates is that soil without life forms means that anything sitting on top will take forever to decompose, although you can see green mould or fungal activity beginning on the inert side. There are various ways a heap breaks down, and it's not just burrowing insects,but also bacterial and fungal activity that may not be readily visible.

This 'fun' article here https://www.theguardian.com/lifeandstyle/gardening-blog/2011/sep/02/friday-debate-compost-turning cites two horticultural opinions that say it's not worth it on the strength that life's too short, largely, but in fact, being really scientific and rigorous about managing (turning, controlling moisture and content,covering, etc) compost heaps does mean achieving useable compost much faster.

Ultimately, it depends what you're going to do with the resulting compost from your pile and how soon you want it. If you're just going to put it back into the ground and you're not in any major hurry, or don't have sufficient time to take on the job (and most of us don't) then just leaving it to get on with it is fine. On the other hand, if you have the time and interest, then monitoring,turning, and so on, on a regular basis, will produce compost faster which will be pathogen/weed seed free and suitable for use in potting soil mixes, despite the temporary, short lived cooling and disruptive effect of turning.

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    Thanks for the answer. I come across a piece of interesting research article using integrated vermicomposting and thermophilic composting. sites.bsyse.wsu.edu/ndegwa/main/publications/downloads/… – y chung Dec 27 '17 at 16:24
  • @ychung you thinking of processing sewage as well as garden waste then? – Bamboo Dec 27 '17 at 16:26
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    I think the issue here is the underlying mechanism, the ingredient may be less important (however I should say worms in vermicomposting is a little different than litter feeders). And unfortunately the article does not compare to thermophilic composting alone. In my opinion the frequency of turning should be low enough to allow the detritivores to work well until particle size reduce to a certain point. Then, more turning can be done to increase aeration to achieve thermophilic composting. – y chung Dec 27 '17 at 16:41
  • @ychung but consideration should be given to the question of larger inhabitants of a compost pile - an unturned pile may be a place where fox, hedgehog and other small mammals choose to rear their young, so when you decide its time to start turning, it might be at a time causes significant issues for them. Anyway, doing it scientifically, with all factors controlled, an aerobic, hot pile makes compost in six months - not turning, or turning much later and occasionally, means easily a year or much longer, depending on contents - I know, having done both – Bamboo Dec 27 '17 at 17:42
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    There you go, as long as the pile gets air without turning, it will go quickly. One should adopt one or the other; not turning, using pipes and allowing the little mammals a home and to help with decomposition. By turning frequently, this deters the little mammals, and might delay decomposition a bit but not much. I watched 6' piles of tree chips decompose all winter, I added alfalfa pellets twice. No cover. Lots of little animals enjoyed their winter home. Lots of cool smoking ambiance. Spring. These 6' piles were 6". No little animal problems. No blackberries that used to be there. – stormy Dec 28 '17 at 0:28
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It depends. And so you have the worse possible answer.

The temperature of compost should be not too hot, not too cold. Turning the composts too often (or in cold periods) could stop the decomposition process. On the other hand, on summer, turning it frequently, could cold it down, so that the compost will not "burn", killing the decompositers. And this will give also more oxygen for the bacteria and insects.

In addition, every compost has different ingredients (and different weather), which change the rules. The most experiences gardeners will feel when they should turn the compost (and on what strength). For most of us, it is just trial and error.

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Little burrowing mammals are drawn to decomposing piles, warmth for the winter, food, easy digging. If you turn your piles often the turning is what discourages tenants. I think you are thinking the same thing. You want to turn them very often so that you aren't killing nests of babies.

Decomposition should be aerobic meaning with air. If air is used up or cut off from a part of the pile or the entire pile, decomposition will continue anaerobically. This process gives of methane. Aerobic decomposition gives off CO2. Methane is very stinky. So turning the pile encourages more aerobic decomposition. I think it is faster and more sane to go aerobic.

Turn as often as you want or think about it. Add a little nitrogen fertilizer. Keep it all slightly slightly moist. Add garden soil to the pile, that injects fresh decomposers, bacteria and soil particles. There used to be a litter box material for cats that was simply alfalfa pellets. This was the best stuff to throw on decomposing piles! Nitrogen. Let me know if you are able to find it.

Make sure you have a plastic tarp for the rainy seasons and cold seasons. Important tool to control your decomposing piles holds the heat in and you can control the amount of moisture allowed.

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Consider, if you will, "commercial composting" - while there are various versions of this, one that lights on your question is a long, slightly inclined tube where material is dumped in one end and slowly transits the constantly rotating tube to drop out as finished compost a few days later. It it turned constantly. This does not happen to scale well for home use, but fundamentally, air is always good (if you don't cool off & dry out the pile too much, which is why it does not scale down well.)

The main "composters" are thermophilic (heat-loving) aerobic (need oxygen) bacteria. If detritivores are significantly contributing to the breakdown of your materials, you are arguably "just letting stuff rot (and be eaten)", not composting. You are certainly not going to get results as fast that way.

Fallen leaves at a household scale are best processed a different way - turn them into "leaf mould" by wetting, compacting, and storing as they will break down easily by fungal action over the course of a few years, needing no aeration to do so, and they do not contain seeds that need to be killed. Fallen leaves are a terrible compost ingredient, as they impede aeration (though they would perhaps be fine in the aforementioned commercial system which has a very aggressive aeration mechanism.)

  • Oh boy, do I agree with your comments about composting leaves, in total agreement - but in my experience, you can get good leafmould compost after 1-2 years,depending on warmth of climate, by using the bagging method separate to the compost heap. – Bamboo Dec 28 '17 at 0:51
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A couple of points to consider....

If I turn a pile of compost, with various critters that burrowed their way into the middle, aiding the process, and my turning the pile moves them to a more peripheral location, will those critters say "dang, I'm leaving THIS pile," or will they burrow their way back into the middle, where they clearly prefer to be, affecting more materials that they would not have otherwise interacted with?

By the same token, if you have one area of the pile that is decomposing very well, you have this quandary - You have a combination of temperature, microbes, nutrients, moisture, light/dark in that area. Composting occurs, you then have finished compost in that ideal area, but are now out of the raw un-composted materials in that location. On the other hand, you have plenty of raw materials elsewhere, but those locations are not as ideal. Turning the compost distributes some of those needed microbes (which now exist in greater amounts) to other areas, moves the finished composted materials out of the ideal location, where they are no longer needed, and moves/rotates the materials that still need to be composted into an area where they can be more efficiently used.

  • Those critters wouldn't even imagine making a home in something that is not stable. Critters aren't dumb. If those critters see the pile is stable they will make a home. Now get this. Those critters actually are part of the decomposition process and make AIR tunnels to get air flowing to their nests. They eat the fresh material and poop it back out, furthering the decomp process. Decomposers multiply very very quickly. Giving them new material, new air, moisture...best is to add nitrogen as well...they go nuts. Interrupting and turning a pile is a great thing. It enhances decomposition – stormy Dec 28 '17 at 0:20
  • Critters won't burrow back to the centre of a turned pile - it'd get too hot, even if they didn't mind the disturbance. – Bamboo Dec 28 '17 at 0:53
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    They do mind disturbance. An unturned pile can get very hot if there are lots of sticks or pipes included to allow air. Critters will find a spot with stability NEAR the heat. And food source. If there isn't regular disturbance. – stormy Dec 28 '17 at 0:56

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