Composting Reduces Manure Volume
By Ellen Crawford, North Dakota State University Extension
Composting could solve manure storage problems.
North Dakota’s long, cold winter has led to larger than normal accumulations of manure and bedding, and may delay producers’ fertilizer application.
Producers typically apply manure as a fertilizer in the spring before planting and in the fall after harvest. However, many producers may skip the manure application this spring. That could result in manure storage facilities reaching full capacity.
Composting is a possible solution to the manure storage problem, according to Chris Augustin, nutrient management specialist at North Dakota State University’s Carrington Research Extension Center.
Composting kills weed seeds and pathogens, and reduces manure volume. Research indicates that composting reduces manure piles by half to two-thirds. Compost also is less dense than raw manure. This reduces hauling costs because producers have less and lighter material to apply on a field.
“Composting is more than piling manure and letting it sit, though,” Augustin says. “Composting is a speedy decomposition process. The bacteria and fungi responsible for composting are indigenous to the pile. It is our job to create a habitable environment for the decomposition organisms.”
Manure composting requires 20 to 40 parts of carbon for every part nitrogen. This is equal to about 80 percent cattle manure and 20 percent straw bedding. Manure is the nitrogen source and straw is the carbon source.
The compost pile also must have adequate air and water. Fifty percent of the pore space needs air and the remaining 50 percent needs to be filled with water. The pile should feel like a well-wrung-out rag, Augustin says. If water drips out of a handful of compost, it is too wet. If it doesn’t feel damp to the touch, then it is too dry.
After piling the compost, the pile should heat to more than 130 F in two or three days. If the pile does not heat, then one of the four factors (carbon, nitrogen, air and water) is not in the pile in the recommended amount. The temperature should remain above 130 F for a couple of weeks and then decline. Once the temperature falls, the pile needs to be turned.
Producers can buy implements designed for turning compost, but turners can be expensive. One alternative is to use bucket tractors to turn piles. Also, Soil Conservation Districts in Wells, Stutsman and LaMoure counties offer custom turning services.
Turning the pile introduces oxygen into the compost and will stimulate the microbes in the pile to continue heating.
“The idea is to move materials from the outside of the pile to the inside of the pile and add air to the system,” Augustin says.
The duration of subsequent heating cycles will shorten with each turn. After three to five turns, the manure is composted.
Augustin suggests letting the compost sit for a few weeks to allow it to cure. Applying compost that has not cured can cause phytotoxicity issues. Once the pile has assumed ambient temperatures, it is ready to be used as a fertilizer.
However, compost needs to be sampled for nutrients before it is applied on a field. About15 percent of the total nitrogen, 30 percent of the total phosphorus and 30 percent of the total potassium in the compost should be available to the crop that’s planted.
