One phrase I’ve said so many times that I might soon get it tattooed on my forehead: aged manure is not composted manure!
Proper composting needs regular, active management with the right combination of temperature, size, moisture, oxygen, and carbon to nitrogen ratio to keep the microbes happy and make the piles break down into compost. It’s is as much of an art as it is science.
Temperature
The temperature of a pile indicates its health. In There are three temperature phases: (1) warm-up, which is the time from pile construction until the internal temperature reaches 105ºF, (2) thermophilic, in which the microbes do the heavy lifting of decomposition, and (3) cool curing, when composting is complete, and the material stabilizes. Throughout all three stages, heat should be monitored with a thermometer probe.
If your pile should be in the thermophilic phase but will not heat up to at least 110ºF, or it’s reaching temperatures over 160ºF, there might be a problem with one or more of the components below:
Size
The size of a compost pile will be determined by the size and needs of an operation. Some will have one large pile, while others will have multiple, smaller piles that may be at different decomposition stages. A compost pile should, at minimum, be three-feet square by three-feet deep. Anything smaller generate the necessary internal heat. For maximum size, do not exceed the size that your machinery can effectively turn and mix.
Particles should be small, but not too small. Particle sizes of 1/8 inch to two inches are considered best. Manure is crumbly and can be broken into bits of that size, but coarse bedding such as corn stalks may need to be shredded if they are too large.
Moisture
Moisture is crucial for the reactions needed to break down organic materials and regulating compost temperature. The optimum level for composting is 50 – 60 percent moisture, but many of the microbes will still do their job at 40 to 65 percent.
To check moisture levels, use the “squeeze test”. While wearing gloves, squeeze a handful of compost. If water drips out, the compost is too wet; if you open your hand and the compost crumbles apart, it’s too dry. Compost with optimal moisture will hold its shape without dripping, like a damp (not wet) washcloth. Do this a few times in different areas to get a sense of the overall moisture. Covering the pile with a roof or tarp protects from both rainfall and sun exposure. Additional aeration and turning can also help dry wet compost. And a too-dry pile can be moistened with water from a spray hose or bucket.
Oxygen
Aerobic conditions are required for composting. The need for high oxygen levels is greatest at the start of the process. Five percent oxygen in the pore space is the minimum;10 to 15 percent is optimal.
Within the compost pile, oxygen will be most abundant in the outer layers; and the compressed inner core of the pile will have the least pore space, and therefore, the least oxygen. Turning and mixing the compost is important to spread oxygen throughout the pile, bringing the center of the pile to the outside, and the outside to the center.
Ratios
Carbon sources in composting are typically bedding. Nitrogen can come from both manure and bedding, depending on the type. The optimal ratio for composting is between 25:1 and 30:1.
If the C:N is lower than 20:1, nitrogen will be lost to the atmosphere as ammonia. To remedy this, you can add carbon sources such as straw or wood chips to the pile. If it’s higher than 40:1, nitrogen will be tied up by the excess carbon. To remedy this, add nitrogen sources to the compost pile such as grass clippings or hay.
If the pile is not breaking down the way it should, and you’ve ruled out other factors as the culprit (moisture, size, etc.), you may benefit from sending samples of the compost pile to a manure lab to test for C:N.•
