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Knowing how often to turn compost depends on a number of factors such as size, the composition of the pile, and the composting process you are using. This means there is no definitive answer and you should avoid advice that tries to give you one.
It isn’t though, that complicated and there are general rules that you can follow to make sure you turn your composting pile enough and at the right time.
Do you need to turn your compost pile?
Composting is a chemical reaction caused by the carbon and nitrogen content of the organic materials that you are composting. Oxygen and moisture can speed up or hinder (too much moisture) this process as they act as activators for the chemical reaction.
There are two main types of composting. aerobic and anaerobic and several different composting processes you can use for each type.
Aerobic composting requires oxygen as an activator to break down the materials, whereas anaerobic composting does not require oxygen but is a much slower process.
Turning your compost pile helps keep it aerated and allows for better air circulation which will help speed up the process of breaking down the material. It also helps prevent pests from getting into the pile.
As the main reason for turning compost is to aerate the pile if you are using an anaerobic process you don’t need to turn your compost.
The majority of compost piles though are aerobic as this is a considerably faster method of achieving finished compost.
When to turn aerobic compost piles
Unless you are using an anaerobic composting bin or are trench composting, your composting is going to be aerobic and will probably need turning. There are two principal processes that can be used with aerobic compost piles, regular cold composting and hot composting.
It is the differences between these two processes that lead to divergence, as in hot composting turning plays a pivotal role in the success of the technique.
Turing compost pile when cold composting
Cold composting is the most standard method of composting. You build up your pile in layers of green and brown organic materials. The pile should have a carbon to nitrogen ratio of 30-35:1 (C/N) when finished and be slightly moist (important not soaking wet).
If you have a pile with this carbon to nitrogen ratio, and if you turn your pile once every ten to fourteen days you should get finished compost in around three to four months.
There are though no hard and fast rules to this. The more you aerate the pile the more oxygen gets into the pile which helps quicken the decomposition process. If you turn your pile slightly more, turning it every seven days, you could see finished compost in two to three months. 
You do not actually have to turn a cold composting pile because decomposition will eventually take place but without oxygen, as an activator in the chemical process, it is going to slow down the decomposition of the pile considerably. Instead of having finished compost “black gold” in around three months, it could take a year or even longer, depending on the make-up of the pile.
Turing compost pile when cold composting
Hot composting (thermophilic composting) is all about speeding up the composting process. It does this by elevating the temperature of the pile. This is achieved by increasing the nitrogen and oxygen content of the pile which causes the pile to heat up and the microbes, that eat through the organic material and turn it into finished compost, to thrive.
You can read in more detail about the hot composting process here but in brief, you construct your pile with higher nitrogen-rich content, reducing the carbon to nitrogen ratio to 25:1 (C/N) or just under.
This will cause the chemical reaction to quicken elevating the heat to between 130-150 F. To help and maintain this oxygen need to be present in the pile and this is done through turning.
With hot composting, you would need to turn the pile every two to three days. This would produce finished compost in around three to four weeks, much quicker than cold composting.
The exact turning schedule though is dependent on maintaining the heat at the center of the pile. You would use a compost thermometer to monitor this temperature and turn the pile if the temperature began to drop during the first ten days.
What are the best compost turning techniques?
There are several ways to turn compost. Some people turn compost by hand while others use a tumbler. Tumbling is a great way to turn compost because it breaks up large pieces of organic matter and mixes them together.
The type of turning you choose is likely to be dictated by space, time, and your basic comfort level. The key to turning compost is to do it regularly. For example, if you have a large pile, it is easier to turn the pile all at once rather than a bit at a time. For these larger piles, a front-end loader, tractor, or backhoe with a front-end loader attachment can be used if one is available to you.
However, if you have a small pile, it may not take a long time to turn the entire pile at once. Also, if you are new to composting, you may want to start with simpler methods like pitchforks, shovels, etc.
What problems can turning a compost pile cause?
The one thing to watch out for when turning is to avoid the compost materials becoming compacted, as this will stop oxygen from getting to areas of your pile. Make sure as you turn to break up any compressed for clumpy areas of the pile.
Should you turn over a compost pile after it rains?
It isn’t good for your compost pile to get too wet. When constructing your pile with cold composting you should initially have a layer of brown material on top. If you are expecting a prolonged few days of rain you should cover your pile with a tarpaulin.
If your pile does get wet then you should turn the pile as this will help excess water drain out from the pile and stop the material from becoming too saturated.
Other reasons that will influence if and when you turn your compost?
- When you first start building your compost pile, it may take longer to build up than you expect. In this case, you may need to turn the compost pile more frequently to speed up the process.
- When you have a large compost pile, it may become compacted. To break up the pile, you may need to rotate it more frequently.
- When you have a wet compost pile, it may be easier to turn it.
- After a rain, you may need to flip the compost pile to allow water to drain off.
- If you have a compost pile that contains weeds, you may need to remove them before turning the compost.
- If you have a small compost pile, it may not need to be turned as often.
- If you have a large compost heap, it may be easier and faster to just move it around instead of turning it.
- When cold composting you may want to leave the compost pile alone for a while after it has been turned. This allows the compost to settle down and decompose even further.
Summary | How often to turn compost
As you can see deciding how often to turn compost depends on many different factors. If you feel that your composting pile is not progressing as fast as you would like then turning your compost pile is probably the first step to take.
Ultimately, how often to turn compost will come down to experience and feel. The more composting you do the more you will instinctively know how often to turn compost.