It seems that there is a never-ending supply of manure in pastures and feedlots. Unfortunately, storage options can be limited in a lot of cases and transportation is often expensive.
Many livestock owners give away manure to local gardeners or neighboring farms. Some reapply manure on their own fields to add nutrients and reduce fertilizer costs.
It is important to keep in mind that before manure is applied on any garden or field, it should first be composted. While we often associate the word “compost” with food scraps and garden activities, livestock manure can be composted as well and used on the farm.
Composted manure can improve soil health while reducing the need for storage and transport. Soil fertility, water holding capacity and habitat for many beneficial microorganisms improves with the addition of compost to a field, and up to 80% of volume and mass is reduced compared to liquid manure.
Furthermore, composting manure reduces the viability of weed seeds dramatically, reducing the need for herbicides used later in the growing season. Composting can also reduce pathogens, including Escherichia coli, Salmonella and Listeria commonly found in manure.
Composting involves microorganisms responsible for breaking down organic matter to produce an excellent soil amendment that will improve soil structure and soil fertility. Some management of the composting process is required.
Where to compost
The first decision to be made is where should the compost pile go? Areas that are well-drained are a good place to start. Avoid placing compost piles near waters of the state and in poorly drained areas of a field. Also, avoid areas with coarse soils.
Place manure into windrows 10 to 12 feet wide and between 4 and 6 feet high, or you can use dry stack piles with a minimum volume of 1 cubic yard (3’x3’x3′), although actual size will depend on the total size of the pad as well as the equipment used to turn the pile. Pads can be either concrete or just compacted ground. Windrows should be parallel to a slope of 2-4% — ideally, drainage from a manure compost pile should be directed towards a containment pond.
Temperature is one of the most important factors in the composting process. In piles and windrows, temperature will fluctuate during the composting process. Within two days, temperatures in a compost manure pile or windrow should reach over 120°F. High temperatures between 131 to 150°F are needed to kill weed seeds and pathogenic organisms.
However, temperatures that reach above 160°F will reduce the number of beneficial microbes needed during the decomposition process. When temperatures get to this point, reducing windrow or pile size, improving air circulation or adding materials with high carbon content can reduce the temperature to an acceptable range.
Moisture can become an issue if not checked during the composting process. Moisture should range between 40-65% of total pore space in a pile. While measuring devices exist for obtaining accurate readings for moisture content, an easy test is to just squeeze the compost — no water should drip from the compost when squeezed. Water can be added to a pile that is too dry. And, of course, wash your hands after handling composted manure.
Access to oxygen is required to maintain the microbial populations needed during the composting process. Piles that are not turned will decompose more slowly and emit a rotten-egg smell. Aeration, or mixing piles, brings in the oxygen required for the composting process.
Large operations often use turner implements or windrow turners. Smaller operations can use equipment such as a bucket tractor or skid steer to aerate piles. Passive aeration methods can be used to reduce the need for mixing piles and include perforated pipes within a windrow with the addition of porous materials like woodchips. This type of system requires windrows or piles to be placed over and covered with compost to keep piles insulated and maintain moisture levels.
Carbon-to-Nitrogen (C/N) ratio is another key factor of the composting process. This ratio should be between 20-to-1 and 40-to-1. If nitrogen is too high, manure piles will begin to wreak of ammonia. When this occurs, adding materials that are higher in carbon, such as woodchips, can bring the ratio back into the appropriate range.
The C/N ratio for manure depends on livestock species and what they were fed among other variables. For example, the average cattle manure has a C/N ratio of 19:1, while horse manure has a ratio of 30:1. Swine manure is often around 12:1, and poultry litter can vary between 6:1 and 25:1. Manures with ratio values below 20-25 should be blended with higher carbon materials such as sawdust, straw, woodchips, and leaves.
When is it ready?
Once temperatures stabilize, the composted manure is cured over the next month. Manure that is ready will have temperatures at ambient levels and will not produce ammonia or foul odors. Maturity can also be verified at laboratories or tested with kits that check carbon dioxide and ammonia emissions.
Mix mature piles to ensure nutrient uniformity throughout the product. Applying composted manure that has not finished curing has the potential to become phytotoxic and can bring in unwanted pests in addition to producing an unpleasant odor.
In order to match crop needs, nutrient levels should be checked through a manure test. Contact your local Extension office for more information on manure testing.
It is important to have a sound manure management plan and to use the appropriate designs for manure facilities, which can be utilized as part of an affirmative defense for adverse claims. For assistance with design of manure facilities and other considerations for manure management, see Bulletin 604: Ohio Livestock Manure Management Guide (go.osu.edu/bulletin604) or contact your local NRCS office.
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