Anyone with the right tools and a strong back can turn a compost pile, but a few tricks make the job easier. After a week or two, most compost piles settle by as much as 30 percent; settling is due partly to gravity and partly to decomposition. As the pile sits, it tends to become more dense, compacting as it loses air from the interior. Consequently, a shovel isn’t the best tool for turning a compost pile. A composting fork works better because it breaks up compacted material.
The simplest way to turn a pile is to move material from the pile and restack it alongside. With this method you handle all the material just once. For composting systems in which turning the pile regularly is desirable, the best option is a multiple-bin setup. Each time you turn the pile, you just move it to the next bin. A more time-consuming method is to empty the bin and refill it with the same material. That means handling the material twice.
Turn the pile by stripping off the top and outside (if it’s a free-standing pile or one with removable sides) first, piling them in the center of the new pile. The object is to end up with the material that was on the outside of the original pile resting in the middle of the restacked pile. Conversely, the material that was in the center of the original pile should be on the outside of the new pile. This doesn’t require great precision. To the degree that you’re able to move material around, you’ll promote uniform decomposition; the finished compost will have a more consistent texture.
If the compost seems dry, this is a good time to wet it. Put a sprinkler on the location where the turned pile will be to wet all the material as you turn it.
As time passes, the decomposing matter becomes coffee brown and more evenly moist. A 4- to 6-inch layer of gray powdery fungus usually lies under the dry material on the cooler, outer parts of the pile. You can sometimes see steam radiating from the center of the pile as you move the material. As before, try to shift the outer material to the center and the central core to the outside.
Knowing When to Turn a Pile
You must turn the pile frequently if you want to produce high-quality compost in the shortest possible time. Turning it oxygenates the pile and mixes the materials. It also gives you a chance to add moisture if necessary.
Researchers have learned that decomposition occurs most efficiently when the temperature inside the pile is between 105 degrees and 130 degrees. They have also learned that it’s best not to turn a pile when its internal temperature is in that range. Turn the pile when the temperature is higher or lower.
For best overall results, watch the compost thermometer and turn the pile when the temperature is between 130 degrees and 140 degrees. Once the pile is hot, turning it causes the heap to cool down, then heat up again. By turning the pile every time it nears the 140 degrees mark, you keep it operating at its peak. Also, you prevent the pile from getting too hot and killing beneficial organisms.
If the pile contains a variety of materials with a carbon-nitrogen ratio approaching the ideal 30 to 1, then you may have to turn the pile every other day. This method of intervening to sustain the optimum temperature should give you finished compost in about three weeks.
Such a speedy process involves some tradeoffs. Although most disease pathogens die when exposed to 130 degrees for 10 to 15 minutes, some weed seeds are killed only when they’re heated to between 140 degrees and 150 degrees. If you’re concerned about weed seeds, let the pile reach 150 degrees during the first heating period. Then drop back to a temperature between 130 degrees and 140 degrees for subsequent turnings. Be aware, however, that temperatures beyond 140 degrees kill increasing numbers of beneficial organisms in the pile.
For a more relaxed approach that still involves turning, let the pile heat up and begin to cool. When it reaches 105 degrees, or when it’s just warm to the touch, turn it, placing the outside materials on the inside of the new heap. It will heat up again. When it cools completely, it’s ready to use. The single turning mixes materials thoroughly. The outer layer, which hasn’t had a chance to decompose yet, will be able to heat up. This method kills weed seeds and pathogens with a minimum of labor.