Storing Manure on Small Farms
Published on Thu, 10/24/2019 - 3:22pm
Storing Manure on Small Farms
By Fred Kelly: USDA Natural Resources Conservation Service
Why Do Small Farms Need Manure Storage?
Accumulated manure can cause health, odor, pest, and water quality problems if not properly managed. One option is to collect the waste daily, load it in a spreader, and spread it on cropland, hayland, or pasture (often referred to as a “daily haul” system). This is time consuming and also has to be done regardless of the soil moisture, weather, or time of year. Spreading during rain, on saturated or frozen soils can cause compaction or lead to offsite runoff of manure. Growing crops can also be damaged during spreading.
The alternative to daily spreading is to stockpile or store the manure for a period of time, at which point it may be spread or hauled away and utilized beneficially elsewhere. Even though the number of livestock on your farm may not be large, enough manure will be generated to pose a problem if planning is not done.
Example: A single horse can produce 50 pounds of manure per day which translates to 11 cubic yards and 9 tons annually. The manure and bedding produced by this horse in a year can exceed 25 cubic yards. This would require a storage area of about 12 feet by 12 feet with an accumulated depth of 3 to 5 feet for one year of storage, depending how much decomposition and compaction of the manure takes place.
For more, see Manure Production and Characteristics to calculate the amount of manure produced by common farm animals.
Principles of Manure Storage
Regardless of the type or size of manure storage, there are a few basic principles to always follow:
1. Keep the clean water clean. Any up-slope surface run-on should be diverted around the manure storage or animal lots by creating a small berm. Rooftop water can be directed via gutters, downspouts and possibly underground outlets so that it goes around animal lots and manure storage.
2. Treat the dirty water. Any rainfall landing on the manure pile or the livestock concentration areas should (preferably) be retained in the structure or settling basin. Over time, the water evaporates, leaving behind the solid materials to be collected and spread on fields. The liquid can also be directed to a treatment area, such as a well vegetated filter strip. The plants will slow the flow, settling solids (filtering the runoff) and utilizing the nutrients as they grow. This option requires regular management as the liquid flow may eventually cut a channel and create an unobstructed path to creeks, streams, ponds or other clean water. The solids from the manure may also accumulate and smother the vegetation. The goal is to direct the drainage over the vegetated area as evenly (like a sheet) as possible and regularly harvest the vegetation as hay or silage to remove prevent build up of nutrients.
3. Avoid flood-prone areas. Flood waters that can reach a manure storage location will transport manure downstream and cause extensive water quality problems.
4. Accessibility. Store the manure where it is easily accessible to load and unload. Efficiency is important in order to properly manage the manure facility. Make sure you can access the site in all types of weather conditions. If it is difficult to access the site, you are less likely to regularly manage or maintain it.
5. Avoid steep slopes when siting your storage location. The steeper the slope, the more difficult it is to manage the storage area, and the greater potential for offsite runoff. It may be necessary to build a small dirt berm (do not use manure for the berm) to prevent storm water from leaving the area and running downslope.
6. If you spread the stored manure on your own land, do so following a nutrient management plan that establishes the spreading rate per acre to match the nutrients available in the manure to the needs of the crop.
Manure Storage Considerations
Storage can be very simple or quite complex; very inexpensive or quite pricey. The choice depends on a number of factors.
The first thing to decide when contemplating storage is the location. The spot has to be very convenient to the animal housing, but there is more to consider. The storage must be located well outside of any stream floodplain, and should have a slight slope for drainage, but not slope so much that runoff can cause problems. It is important to prevent manure from being washed offsite to streams or lakes. Manure contains potential pollutants when it is not managed correctly. The bacteria, phosphorous, nitrogen, and organic matter pose risks to aquatic organisms and humans.
Odor management is another consideration when siting a storage facility. Look at wind direction as relates to dwellings. The final consideration is aesthetics. If possible, keep the facility out of view of neighbors and passers-by. Sometimes a screen of trees and shrubs can help, and also may reduce odor.
The sizing of a storage facility depends upon three factors:
•How many animals are on the farm, and how much of the manure is collected?
•What is the time period the storage will be accumulating manure before emptying?
•How much money is available for building the facility?
From the weights and volume cited above for a single horse, it is easy to see how a storage facility can get large quickly, with just a few animals. Also consider that the ideal length of time permanent storage should have capacity for is six months; the minimum should be 3 months. For information on how to calculate the amount of manure produced, visit Manure Production and Characteristics.
Options for Manure Storage
Stockpiling of manure is just what it sounds like- simply taking the solid manure and soiled livestock bedding and piling it up in a convenient location. This primitive method can be acceptable for the farm with just 1 or 2 horses or several sheep. However, the spot must be compacted and sealed so that rainfall landing on the pile cannot leach pollutants into the soil and ground water. Sometimes gravel in a packed pad works well, or stone dust is used. The area approaching the pad needs to be firm also to prevent rutting in wet periods. Also, the pile should have a very slight slope (1-3%) to facilitate drainage to a vegetated filter strip.
A stockpile can be covered with a plastic tarp to reduce odors, flies, and leaching concerns. Rainfall will run off to the edges and never penetrate the pile. The tarp will need to be anchored securely all around the edges. A filter strip of vegetation or (preferably) a small dirt berm is still needed on the downslope side.
This is probably the most common and practical choice for the small livestock operation. A dry stack facility has three walls to contain the manure. The best ones have a poured concrete floor. The floor is slightly sloped for drainage out of the facility, and the drainage runs to an adjacent vegetative filter strip. The walls of a dry stack facility will be a minimum of four feet high. The walls, especially the back one opposing the entry, must be stout since the manure will be exerting outward pressure as the pile grows higher. Also, clean out is usually done with a front-end loader, and pushing will be done as the manure is scooped up. The walls can be poured concrete, cinder block, horizontal timbers, or vertical timbers. Secure anchoring below the frost line is crucial.
Cost: Moderate to High
The treatment of raw manure through composting is gaining in popularity. The final product is crumbly, low odor and resembles rich topsoil. It is often highly marketable. Composting reduces the amount of available nutrients, kills pathogens, reduces odor, and reduces manure volume. However, it requires management. A pile of manure left alone is not composting- it is decomposing, which is a big difference.
Composting requires a balance of nitrogen, carbon, oxygen, and liquid. When things are running properly, the center of the pile will reach 140 degrees, which kills pathogens and renders a relatively stable product. An untended decomposing pile has a nearly anaerobic core that produces objectionable odors when broken into. Although the center is often hot, it’s not hot enough to sanitize. Composting requires taking the pile’s temperature, and turning of the pile regularly to mix and aerate. Sometimes it will need water; other times it will need to be covered so it does not become saturated and lower the oxygen level to unacceptable levels.
Turning the pile is usually done with a small tractor equipped with a front bucket loader. There are many ways to set up the composting site. It could just be several long windrows, 4 – 6 feet high, on compacted ground or compacted gravel, or concrete. Or, there may be several small dry stack-type bays connected together side by side, and the manure is moved from one bay to the next, and the manure is mixed and aerated in the process. Manure and bedding, when properly mixed, can be transformed into compost in as little as six weeks.
Liquid storage is used by many larger dairy or swine farms. The waste is diluted with stall wash water and pumped to a lagoon or other holding location. From there the liquid effluent and the solids are pumped into an injector tank and spread in the field as a slurry, either sprayed on the surface or injected into the soil. Or, the effluent is spray irrigated and the solids are separated and spread in a conventional fashion. This type of storage and management system is usually the most complex and expensive, and is usually not practical for smaller livestock operations.
Sometimes, the best solution is to simply have a dumpster or some other form of semi portable holding structure, and place the manure in there. When needed, a waste management purveyor can pick it up for beneficial re-use on cropland that can use the organic matter and nutrients. Remember to still have a vegetative filter strip to treat the leachate draining from the dumpster as it drains away.
If the amount of manure being generated daily is small enough, a small manure spreader can serve as the storage device. When full, simply hook up the tractor and spread the waste in the cropland or hayland according to a nutrient management plan. Caution, though- if applying to pastureland, it is important to spread the manure about four weeks before a grazing cycle. Smothering of grasses can occur if the manure is applied too heavily. Parasite eggs in raw manure may cause an infestation problem on pastures.
Vegetated Filter Strip
It is crucial to have a vegetated filter strip to treat the runoff water coming from a manure pile or a concentrated livestock area. The combination of grass uptake, soil filtering and adsorption, and biological processes in the top inches of soil significantly reduces pollution potential of manure runoff. The filter should be established in a vigorous, thick stand of grasses adapted to the soil conditions at the site. Animals should be kept off of it, and it should be hayed at least twice a year to remove nutrients and encourage growth. On a flatter slope, the strip should be a minimum of 30 feet wide, wider if slope is steeper. A better option than a vegetative filter strip is a Vegetative Treatment System.
Managing Stockpiled Dry Manure on Small Farms
Flies and odors from stored manure can be reduced if good management is practiced.
• Keep the manure as dry as possible.
• Remove manure from the farm regularly during fly breeding season.
• Try not to use insecticides or larvacides; naturally occurring fly predators- tiny, non-stinging wasps and parasites, are beneficial to the pile. Wasps are active during fly season and their activity is better in dry manure.
• When cleaning out the storage, leave a couple of inches of dry manure over the bottom of the storage area to provide a population of fly parasites and predators. Manure removal can be staggered to leave one section per week to supply fly predators and parasites.
• Remove a winter’s stockpile of manure during cold weather (<55°F) before fly breeding season.
Barnyard and Corral Management
Manure should not only be removed from stalls and barns, but corrals, barnyard areas, and sacrifice areas should be regularly cleaned to reduce flies, odor, and the potential for mud. A box scraper, skid loader, or tractor and loader can be used to remove manure built up on the surface of these areas.