Some composting systems recommend regularly turning compost piles. For example, the Berkely method recommends turning compost every single day until the compost is finished.
Other systems recommend turning compost infrequently, or even not at all.
Both systems can work – and both come with pros and cons. So in this article we’ll examine the different factors involved so you can decide how often you need to turn your compost .
Speed versus quality and quantity
As we saw in the science of composting, microbes need oxygen in order to turn waste into compost. Turning compost brings oxygen into the pile, speeding up the composting process. This can produce remarkable speed – for example, the Berkely method can produce compost in just 18 days.
However, turning compost is not the only way to ensure oxygen reaches microbes. Compost piles absorb oxygen even when they are not turned regularly, and this can be improved when bulking materials are used in the compost pile.
It’s also possible that frequent turning may have some negative effects. Some studies, such as those by Getahun et al and Zhang et al, suggest that frequent turning leads to nitrogen and carbon loss.
In Sustainability of Modern Composting, William Brinton states that turning compost also leads to a significant loss of organic material – and the more you turn compost, the less you get at the end of the process. Brinton also found that turning compost only increases the oxygen level in the pile for 1.5 hours.
Of course, for a commercial system, time is money. Turning the compost produces compost faster, which means a shorter time from the start of production to sale, although this has to be offset against the increased cost and fuel involved.
Even if you are an amateur gardener, if you are starting a new project, you may also need compost quickly in order to rapidly improve the quality and structure of the soil. In contrast, compost that is never turned can take a year or more before it is ready.
However, for most non-commercial gardeners, a system with less turning could produce better-quality compost. Each compost pile may take longer, but the absolute quantity produced per year will not be reduced. In fact, as turning compost can lead to organic loss, you may produce more compost overall with a limited or zero turning schedule.
Time and energy available
For many gardeners and farmers, turning compost regularly is too much of a commitment.
In fact, when composters think they need to turn compost regularly, they often quit. Joseph Jenkins, author of the Humanure Handbook, talks about a project to teach Brazilian farmers how to make compost. Three years after starting the project, they had all quit.
Why? Because turning the compost was just too much work.
Even for professional systems, turning compost is expensive and creates additional use of fossil fuels which is bad for the environment. For the amateur gardener – especially those with large heaps and bad backs – frequent turning may just not be worth it.
How well is your pile constructed?
A well-constructed pile can ensure that more oxygen reaches the microbes in your compost heap, reducing the need for turning. You can achieve this by using bulking materials to create Free Air Space in your compost heap. A key consideration will be whether you have access to enough bulking material. Without bulking material, you may need to turn your compost more frequently.
Some composters also increase the flow of oxygen to their pile by raising the compost off the ground, allowing air to flow to the compost heap.
Some composters believe that compost should not be turned in winter, especially in colder climates. The idea here is that heat that is generated in the center of the compost could be lost when it is turned.
While that seems to make sense, a 2008 study by Sandra Tirado looked at the impact of turning frequency, pile size and seasonal variability on composting. found that season had little impact on the final quality of the compost. The one area which did impact composting was the increased moisture. However, this did look at commercial compost making, and it is possible that smaller piles used by amateur gardeners may be more prone to heat loss.
Another factor to consider is the amount of material you have in different seasons. From spring to autumn, your garden will be generating a large amount of material. It may well be worth turning your compost to speed up the process, create space for new material, and to ensure you can apply compost throughout the gardening season. In the winter, there is little material to add, and you can afford to let the process slow down, as your compost will have several months to mature before spring.
Many guides recommend regular turning of compost. However, for many gardeners, this is neither feasible nor necessary. What’s more, a number of studies suggest that regular turning may reduce the amount of nitrogen and organic material in compost. It is also possible to create good compost without any turning, although the process is likely to take longer.
However, I have found with my own experiments that turning a compost heap once or twice leads to the compost heating up again and speeds up the process significantly. It’s also an opportunity to examine the compost pile and apply water to any dry layers. This last year I have also used a compost aerator to add further oxygen to the compost without having to go to the significant effort of turning over half a ton of compost!
I suggest individual gardeners consider how these factors impact them. Consider how fast you need compost, how much time and energy you have, and whether loss of organic matter matters and you will have your answer. But most of all, don’t let the frequent advice that you must turn the compost regularly stop you from making your own compost.