Tony O’Neill, gardener and author of the popular “Composting Masterclass” and “Your First Vegetable Garden,” combines lifelong passion and expert knowledge to simplify the art of gardening. His mission? Helping you cultivate a thriving garden. More on Tony O’Neill
How much effort you put into making compost is your choice. It’s worth noting that turned-managed piles produce superior humus free of pathogens and weed seeds.
Composting that follows turning routines based on internal temperatures, humidity levels, and times can ensure a uniform, quality decomposition process. How, when, and often a compost batch needs turning depends on the batch composition, method, and internal and environmental factors.
Why Do We Turn Compost?
In a managed hot compost process, compost is turned to:
- Ensure that outlying material is brought to the center where active microorganisms can decompose it
- Avoid anaerobic conditions caused by the collapse of the center as it becomes finer
- Incorporate air
- Incorporate water
- Evaluate the process dynamics
A combination of sufficient nitrogen, carbon, water, and air causes a flourish of microbial activity, generating temperatures high enough to start a fire.
This is especially true for mixes with lower carbon to nitrogen (C:N) than 30:1. Chicken manure or urea mixes that typically create a C:N of 20:1 need closer management. The level of internal microbial activity can be measured by establishing the core temperature.
The batch’s moisture levels must be between 45 and 60%. If moisture levels drop below 40%, the microorganisms become inactive, and anaerobic conditions set in at levels above 65%.
If oxygen availability drops below 5%, beneficial microbes become inactive, and anaerobic organisms take over. The latter will produce methane, ammonia, and hydrogen sulfide (the rotten egg smell).
Air comprises 78% nitrogen and 21% oxygen, with some argon and carbon dioxide comprising the rest. Water vapor and dust particles are also a constituent of the atmosphere in varying amounts.
When to Turn a Hot Compost Batch
Typically, mesophile organisms are involved in the initial decomposition and survive the first heat spike that may reach temperatures of 113⁰F (45⁰C) during the first two to eight days.
This first activity salvo lowers the pH of the mixture due to organic acid production.
This will generally mark the first turn.
Thermophile organisms push temperatures above 113⁰F (45 °C), replacing some mesophilic microorganisms.
Thermophiles break down more complex carbon sources, such as cellulose and lignin, transform nitrogen into ammonia, and boost the mixture’s pH (more alkaline).
These two bacteria break down waxes, hemicelluloses, and more complex proteins.
Every time the temperature reaches 165⁰F (74⁰F), the batch should be turned to avoid the death of too many lower-order microbes while allowing the extinction of pathogens and weed seeds.
The Organic Materials Review Institute (OMRI) requires compost that includes animal materials to reach and maintain temperatures of 131 – 170⁰F (55 – 77⁰C) for 15 days and piles to be turned at least five times during those 15 days.
This marks turns 2 to 6.
Which Composting Methods Don’t Need Turning?
There are several ways to escape the back-breaking work of hand-turning compost piles. Options available to garden composters include:
- Bokashi fermentation
- Static Piles
- Trench Composting
Bokashi composting uses cultivated effective microorganisms (EM), a mix of photosynthesizing bacteria, lactic acid bacteria, yeasts, and actinomycetes.
These organisms are used to inoculate bran fiber or rice hulls, which in turn is used to cover kitchen waste in a specialized bokashi bucket. The bucket traps odors and allows the user to drain any fluids.
Once the bucket is full, it is left to ferment for a couple of weeks before being added to a garden bed. You can find out more about bokashi composting here.
Static Compost Piles
As the name implies, static compost is left alone to decompose until the pile has been reduced to usable compost.
Most static piles are fed gradually from the kitchen and yard so that the decomposition rate will vary. As is true for all compost preparation methods, smaller particles decompose more quickly in compost.
It will optimize your composting process to shred the parts you add.
To keep the bottom of the pile partially aerated, use a straw, twigs, or even an oak palette as a base. Some static piles also make use of forced aeration. Find out more here.
Compost is made by feeding red worms on organic waste, such as food scraps and yard trimmings.
Castings are the high-quality compost that the worms produce from this low-quality material. Worm bins are simple to build and can be purchased as well.
Trench composting is the easiest way to reduce waste sent to landfills and benefit your garden’s soil. In trench composting, we bury household scraps in the garden and allow nature to do the rest.
There are some considerations; understanding the process helps me balance my garden’s needs with the waste disposal element. You can find out more about the pros and cons of trench composting here.
How to Make and Manage a Batch of Hot Compost
- Layer and mix green and brown plant materials in the bin, wetting it amply. The initial C: N ratio should be in the region of 30:1
- From day two, start measuring the core’s temperature, turning it when it has reached 113⁰F (45⁰C). Move the batch to the adjacent bin, incorporating the outside material into the center.
- Make sure moisture levels are around 50%. Measure this by squeezing a handful. If the water flows out from your hand, it’s too wet (add some hay). If there isn’t a drop between your fingers, it’s too dry (add more water and keep testing).
- Take daily temperature measurements, turning the batch every time it peaks near 170⁰F (77⁰C)
- Each successive turn, the temperature will be lower, or the time to reach a temperature above 131⁰F (55⁰C) will take longer. This is normal as the batch matures.
- Keep the batch covered once temperatures no longer reach thermophilic temperatures, and allow it to cure before use.
I hope that helps you speed up your process of creating what your soil longs for.