How To Manage Stored Manure And Protect Your Water
Runoff from improperly stored or managed manure can lead to contamination of groundwater and surface water. Land application of manure at proper agronomic rates or composting of manure conserves nutrients contained in the manure and minimizes leaching and runoff of contaminants. Manure storage in an appropriate structure increases a producer’s flexibility regarding the timing of land applications. Storage is also valuable during extended periods of bad weather and when crops are actively growing, making application impractical.
Proper management of stored manure depends on proper design and construction of the storage facility, a good knowledge of the physical and chemical characteristics of the soil and subsurface geologic materials within the storage area, and proper land application of manure once it leaves the storage facility.
Long-Term Storage Options (More Than 90 Days)
Livestock manure can be stored for more than 90 days either in solid, semi-solid (slurry) or liquid states.
- Solid facilities use walls and slabs for piling heavily bedded or frozen manure.
- Slurry facilities use pumps to move manure into storage areas where some solids may be separated from liquids.
- Liquid facilities hold manure in tanks, pits, earthen lagoons, evaporation ponds or bermed areas.
Problems With Leakage
Liquid and semi-solid storage systems, in particular, must be carefully installed and maintained to ensure that they do not leak. Lagoons need to be big enough and lined with earthen or other materials to provide a very low liner hydraulic conductivity of no less than 1 x 10-7cm/sec make this a footnote. Freezing, thawing, wetting and drying cycles, and even earthworm or other animal burrows may cause leaking through a liner. The effective life for properly designed lined earthen pits is approximately 10 years.
Look for the following as a sign of leakage. If a pit has been receiving designated liquid manure amounts and you are adding additional milk house liquids, but the pit has not required pumping, it is probably leaking.
Monitoring wells installed around the pit upslope and downslope can confirm the seepage. Talk with your county Extension agent or contact the Division of Water Quality for more information.
Short-Term Storage (30-90 Days)
Short-term storage of manure is not a recommended practice, because it poses a risk of contaminating surface water and ground water. However, short-term storage is sometimes necessary to hold livestock manure during periods of bad weather when daily spreading may not be feasible, when crops are growing and land is not available for applying manure or when there is a shortage of crop acres to handle daily hauling and spreading of manure without the threat of runoff.
Short-term storage does not replace a properly planned long-term storage facility and livestock growers should develop a plan to reduce the need for any short-term storage system for their operation.
To minimize leakage or runoff from these sites:
- Store manure in pole sheds or other roofed areas to keep rain and snow off.
- Provide adequate bedding in piles to absorb liquids in the manure.
- Clean these areas as frequently as possible.
The best ways to handle any drainage from a short-term storage facility is to channel it into a lined watertight holding pond, storage tank or into a constructed filter strip. In situations where these options are not possible, it may be necessary to build a covered (and curbed) storage area to prevent additional water from being added to temporarily piled manure.
Some solid or semi-solid manure storage systems (such as picket dams) are designed to allow minor drainage of liquids. In these cases the structure design must include containment and/or treatment of liquids that drain out.
Manure Storage Location
When locating a manure storage facility, several factors are important, including the depth to the water table, the type of soils and bedrock, and potential for contaminating water resources. Your county Extension agent or local Natural Resource Conservation Service office can help you with this information.
Locate your manure storage in a site that remains above the water table throughout the entire year. Avoid areas with fractured bedrock or areas with extremely permeable soils (such as sandy soils).
To prevent runoff to surface or groundwater, locate your storage on as low a slope as possible, and downslope from surface water or well areas. If there is a possibility of water contamination, consider alternatives for your manure storage facility.