Beef Manure Management With Dirt Lots
Charles D. Fulhage and Donald L. Pfost
Agricultural Engineering Extension
Natural Resources Conservation Service
Many of Missouri's cattle producers background their calves for later sale or feedlot finishing, either in their own lots or at a custom feedlot. Major problems with feedlots in Missouri are due to high rainfall, which produces high volumes of runoff that can pollute streams, and muddy dirt lots, which reduce performance (Figure 1). This publication shows ways to reduce the problem of muddy lots and to prevent stream pollution.
Cattle confined to muddy dirt lots have reduced performance and feed efficiency.
Missouri Clean Water Law
Most beef cattle operations in Missouri are relatively small pasture-based operations and are not "regulated." Permits or letters of approval are not required for the following animal feeding operations:
- Operations smaller than 300 animal units (AU) in size (except for certain dairy facilities)
- Pasture operations, bare feeding areas within a pasture, or barn lot feeding areas when the cattle have free access to pasture.
One beef feeder animal or beef slaughter animal equals one AU.
However, the Missouri Clean Water Law, in simple terms, states that "it is a violation to allow the discharge of a pollutant or contaminant to waters of the state" without a discharge permit. The Clean Water Law applies to all production enterprises regardless of size. Therefore, beef producers are urged to maintain vegetation on pastures, especially next to streams and bodies of water, and to follow recommended best management practices when collecting, storing, transporting and applying manure to fields.
Solid, slurry and lagoon systems, or any combination, can be developed to meet Missouri Clean Water Law requirements. Any livestock manure management system, regardless of size, must be designed and operated in a manner that will not pollute surface or ground water. Consult local health and regulatory authorities and have all plans approved before constructing any manure handling system. Contact the Outreach and Assistance Center at the Missouri Department of Natural Resources at 800-361-4827 or your local MU Extension center or NRCS office for information about permits and assistance in planning manure management systems.
Current regulations are primarily concerned with concentrated animal feeding operations. A concentrated animal feeding operation with 1,000 animal units (AU) or more is required by state law to obtain a permit from the Missouri Department of Natural Resources (DNR) if it meets each of the following three criteria:
- Animals are confined for 45 days or more in any 12-month period.
- A ground cover of vegetation is not sustained over at least 50 percent of the animal confinement area.
- One of the following size criteria is met:
- Class 1A, 1B or 1C operation (greater than 1,000 AU); or
- Class II operation (between 300 and 999 AU) that discharges through a man-made conveyance into waters of the state or where pollutants are discharged directly into waters of the state which originate outside of and pass through the facility.
If animals normally on pasture are kept in a concentrated animal feeding area for a portion of the year, the total concentrated animal units will determine the requirements for a letter of approval or permit. For more details, see Guide to Animal Feeding Operations, published by the Water Pollution Control Program, Division of Water Protection and Soil Conservation, Department of Natural Resources, or contact the Outreach and Assistance Center at the Missouri Department of Natural Resources at 800-361-4827.
Classification of feeding operations
The requirements are based on the number of animals at each operating location. Table 1 shows the number of animal units in each class of concentrated animal feeding operations. Table 2 shows the number of various animals constituting one animal unit.
Animal unit and size classification
- Class IA
7,000 or more animal units
- Class IB
3,000 to 6,999 animal units
- Class IC
1,000 to 2,999 animal units
- Class II
300 to 999 animal units
Number of various animals constituting one animal unit
- Beef feeder or slaughter animal
- Dairy cow
- Swine weighing more than 55 pounds
- Swine weighing less than 55 pounds
- Laying hens
- Broiler chickens
Voluntary letters of approval: Operations smaller than those listed in Table 1 may not be required to obtain a letter of approval but must operate in a no-discharge manner in compliance with the Missouri Clean Water Law. Operations that do not require a permit may apply for a letter of approval or a permit on a voluntary basis. Operations smaller than Class II (less than 300 AU) may apply for a letter of approval based on best management practices approved by the DNR. This will allow approval of innovative practices that may be more appropriate for these smaller operations than conventional storage and land application systems. Many of the feedlots in Missouri are smaller 300 animal units, and few are larger than 1,000.
Land area requirements
Approval of an animal manure management system by DNR requires that sufficient land be available to receive the nutrients contained in the manure. If you do not own suitable land, a legally binding agreement must be reached with neighboring landowners to allow spreading the manure on their land. A specific form (M121-F, Spreading Agreement) is available from DNR outlining the requirements.
Beef manure management systems
Missouri beef manure management, usually for feedlots rather than for pasture systems, can be classified into three systems depending on the collection, transportation and distribution of the manure on the fields.
Which of these systems is appropriate depends on the amount of bedding and water dilution used by a specific operation or the reduction of moisture content by allowing water to drain off to an approved collection area. Manure can be collected by scraping and transported to a storage area for land application at an appropriate time to make best use of the manure nutrients and when the crop production sequence allows spreading. During storage, water may drain off and reduce the mass of manure to be transported as a solid to the land application area. Runoff from a dirt feedlot may have a substantial portion of the solids separated from the runoff in a settling basin. The settled solids and runoff water remaining in the settling basin may be agitated and handled as slurry. The runoff passing through the basin may proceed to a holding pond (or a lagoon) and be applied to the land by sprinkler or surface irrigation. Thus, dirt lot systems may handle manure using one, two or three systems, based on solids content.
Many beef operations use more than one system. Frequently, most of the manure is spread by the animals while on pasture, thus eliminating the cost of collecting, transporting and distributing the manure on fields. Manure distribution and water quality can be enhanced by such low-cost measures as disbursed salt blocks and mineral feeders and frequent moving of hay feeders, feed bunks and self-feeders. Higher-cost measures include disbursed water supplies to draw cattle away from streamside areas and fencing off buffer strips along streams. A recent trend in beef production is intensively managed grazing, which optimizes forage production as well as manure distribution over a system of paddocks. This method is well suited for cow/calf and backgrounding operations.
Site selection for dirt lots
In the past, many feedlots were located in irregular areas where row-crop farming was not practical. Often the feedlot was located on steep land with high rates of erosion and bordered a ravine or a stream. In other cases, a stream ran through the feedlot and a portion of the land was too flat for good drainage. In these situations, stream pollution was a common occurrence and runoff-control structures were not feasible without compromising the size of the lot.
Feedlots experience problems with both water runoff and air quality. Preliminary site evaluation considers topography, neighbors, present and future livestock numbers and accessibility. Any livestock waste management system, regardless of size, should be designed and operated in a manner that will not pollute surface or ground water.
A land slope of 2 to 6 percent is recommended for good drainage of dirt lots. Steeper slopes can cause excessive erosion. Grade the site to establish the proper slope, if necessary. Lot space is affected by lot slope. Minimum requirements are 150 to 250 square feet per head with 4 percent or greater slopes, 250 to 400 square feet with 2 to 4 percent lot slopes and 400 to 800 square feet with slopes below 2 percent. Another rule of thumb is a minimum area of about one acre of land per 100 animal units for pen space, alleys and feed roads. Soil with 25 percent or more clay is preferred to sand or fractured rock surfaces. Clay soils can develop a manure pack that will shed surface water. When scraping manure off the lot, do not disturb the manure-soil interface that has developed a seal.
With a sloping site, take advantage of the natural slope to plan drainage and equipment placement. Terrain and drainage determines bunk location. Preferred bunk orientation is in a north-south direction with east-west sloping lots. On a flat site, the topography must be shaped. Move earth from the parts designed for solids settling and runoff control, and build up along fence lines and feed bunks. Additional soil may be needed to achieve the desired slopes and drainage. Plan drainage away from feed bunks, waterers and fence lines. Concrete areas along the feed bunks and around the waterers. A 10- to 20-foot-wide slab connecting the waterer slab to the feed bunk slab is recommended.
Maintenance of dirt lots
Dirt lots should be maintained to eliminate depressions where water will collect. The goal is to maintain a 1- to 2-inch layer of compacted manure to form a seal above the mineral soil and keep the lot as hard, smooth and dry as possible. Lots that shed water rapidly and completely have less potential to create odors. Pay special attention to holes and wallows near water troughs and feed aprons where spilled and excreted water may collect even during dry weather. Fill these areas with compacted soil as soon as possible. Remove manure ridges that may cause water to collect in fence lines and near feed bunks and waterers. Cleaning these areas may require small equipment or manual labor.
Box scrapers and wheeled front-end loaders are commonly used to remove manure and fill depressions. The best equipment for removing manure is either a self-propelled elevating (paddle) scraper or a tractor-towed box scraper. The paddle scraper and road grader are precision excavation machines, which produce a smooth surface in the hands of a good operator, even with deep or well-compacted manure. Box scrapers are best in relatively loose manure, whether moist or dry, and often have an adjustable blade depth. Both box and paddle scrapers are commonly used in western feedlots, where manure is collected relatively frequently for dust management in the summer and for shaping pens to improve drainage before winter. Frequent "harvesting" of loose, dry manure improves manure quality for land application and reduces dust emissions in dry weather and slush in wet times.
Pushed equipment, such as dozers and front-end loaders tend to gouge. It is more difficult to ensure that a pushed scraper blade (e.g., front-end loader) leaves an even, smooth surface than a pulled blade (e.g., box scraper). Blades that gouge and scar the surface of a lot reduce its water-shedding efficiency. A combination of a front-end loader for major manure removal and a scraper for final cleaning and grading would be an effective compromise.
Manure harvesting equipment should permit skilled operators to leave a firm, smooth and evenly graded lot surface with 1 to 2 inches of compacted manure on top of the mineral soil. It is hard to prevent some mixing of wet manure with the underlying soil, especially during prolonged wet weather in winter and spring, even with excellent manure harvesting practices the rest of year. But it's worth the effort.
Typical mound construction. Mounds should allow space for all the animals in a pen to lie on the warmest side slope.
Mounds keep animals out of the mud
Mounds improve drainage and provide areas that dry quickly; a dry resting area improves cattle comfort, health and feed utilization. Animals should be able to step off of the mound and onto the concrete feeding apron without having to move through mud. Proper mound construction requires 20 to 40 square feet of mound space per animal unit on each side of the mound. The entire pen of animals should be able to lie on each side of the mound without lying on each other (Figure 2). The mounds should be constructed to allow the animals to lie on the sides of the mound rather than on top. Resting on the top often creates areas where rainwater or urine can accumulate rather than draining off. The top of the mound should be less than 5 feet wide and the side slopes should be at a 5:1 or 4:1 ratio. Mounds oriented east-west allow the animals to use the mound as a windbreak by lying on the south side. Mounds should not impede natural pen drainage and should be constructed so that pen shaping and leveling equipment can travel over and maintain the shape of the mound.
Runoff control methods
Pens should be separated from the nearest flowing water channel by at least 200 feet to allow space for runoff control structures or conservation practices. Water channels include road ditches, streams, waterways and pasture draws. All extraneous runoff needs to be diverted away from the feedlots and roads (keep clean water clean). For new sites, this is most easily accomplished by siting the feedlot on a ridge or elevating the feed road to construct a diversion channel. Runoff control systems usually include diversion channels below the dirt lots to convey the runoff to a solids-separation device, most often a solids settling basin (either earthen or concrete) or a settling terrace.
If a mechanical separation device is used, pumping may be required to elevate the runoff to the separator inlet. The liquid outflow from the solids separation device is usually routed to a holding pond or a lagoon for later land application.
A holding pond should be designed to hold the runoff for the desired storage period; 180 days minimum storage in Missouri (365 days storage recommended).
The design of a holding pond should include a safety volume adequate to store the runoff expected from the feedlot for a 25-year, 24-hour storm plus storage capacity for at least 180 days of manure production, the expected 10-year return rainfall minus evaporation during the storage time, and any influent from other sources. The manure production (solids volume) includes the manure not settled out in the settling basin plus silt from any dirt lots. At lease 2 feet of liquid must be left in the bottom of an earthen basin to keep the clay seal from drying and cracking.
If the open lot surface area contributing to the holding pond is greater than 70 percent of the pond area (as is likely for dirt cattle lots), the safety volume depth is computed using the following formula:
Safety volume depth = 0.67 + square foot lot surface x 0.5 foot per square foot pit liquid surface area
For earthen lot areas, the value of 2,800 cubic feet peracre peryear should be used to calculate the amount of manure and silt solids that would come off the lot area. For concrete lot areas, the amount of manure generated, the percent solids not retained in the settling basin (typically 50 percent) and the desired storage period should be used to size the holding pond. Beef feeders produce about 7.7 pounds (about 0.15 cubic feet) of manure solids per day per 1,000 pounds of body weight, and lactating dairy cows produce about 10.4 pounds (about 0.21 cubic feet) of manure solids per day per 1,000 pounds of body weight.
The expected 25-year, 24-hour rainfall in inches.
The 25-year, 24-hour rainfall varies from about 5.5 inches in northeast Missouri to 7 inches in southwest Missouri (Figure 3). The runoff for 180 days of storage is 60 percent (not 50 percent) of the expected 365-day runoff.
Runoff and rainfall minus evaporation: 1-in-10-year return.
||Feet per year for 1-in-10-year return
||Rainfall minus evaporation
|Mean annual rainfall
||From earth lot areas
||From concrete lots and roofs
||From basin water surface
Table 3 lists the runoff and rainfall minus evaporation values for a 1-in-10-year return. Table 4 lists the runoff and rainfall evaporation factors for a 1-in-10-year return, depending on storage time.
Runoff and rainfall evaporation factors: 1-in-10-year return.
- 365 days storage
- Runoff for all areas = 1.00
- Rainfall minus evaporation for average annual rainfall areas 34 inches to 42 inches = 1.00
- Rainfall minus evaporation for average annual rainfall areas 43 inches to 52 inches = 1.00
- 180 days storage
- Runoff for all areas = 0.60
- Rainfall minus evaporation for average annual rainfall areas 34 inches to 42 inches = 0.70
- Rainfall minus evaporation for average annual rainfall areas 43 inches to 52 inches = 0.90
- 120 days storage
- Runoff for all areas = 0.50
- Rainfall minus evaporation for average annual rainfall areas 34 inches to 42 inches = 0.60
- Rainfall minus evaporation for average annual rainfall areas 43 inches to 52 inches = 0.75
- 90 days storage
- Runoff for all areas = 0.40
- Rainfall minus evaporation for average annual rainfall areas 34 inches to 42 inches = 0.55
- Rainfall minus evaporation for average annual rainfall areas 43 inches to 52 inches = 0.65
- 60 days storage
- Runoff for all areas = 0.30
- Rainfall minus evaporation for average annual rainfall areas 34 inches to 42 inches = 0.50
- Rainfall minus evaporation for average annual rainfall areas 43 inches to 52 inches = 0.50
Example calculation using the runoff factor: Calculate the runoff to be expected from a 3-acre earth lot for the 1-year-in-10 return period and 180 days of storage in an area with a 46-inch average rainfall as follows:
3 acres x 43,560 square feet peracre x 2.8 feet per year runoff x 0.60 runoff factor = 219,542 cubic feet of runoff in 180 days
Note: 219,542 cubic feet x 7.5 gallons per cubic foot = 1,646,568 gallons (This would fill a 100-foot-diameter tank 52.4 feet tall.)
The storage periods recommended by the Missouri DNR for anaerobic lagoons, runoff ponds and pits are listed in Table 5.
Recommended minimum storage periods for design
- Lagoons/Runoff ponds
- Liquid manure basin
Calculate the required holding pond volume for 120 head of 1,000-pound beef feeders spending 100 percent of the time on a 220 feet x 220 feet dirt lot with 1.2 acres draining into the holding pond (based on a rule of thumb for feedlots of 1 acre per 100 head total area) with about 400 square feet per head inside the lot). The lot is in Cole County, Missouri, where the mean annual precipitation is 39 inches and the 25-year, 24-hour rainfall is about 6 inches. The pond must contain the liquid runoff for the wettest year in 10, the solids not settled out in the settling basin, the 25-year, 24-hour rainfall, the rainfall minus evaporation from the pond water surface, and have at least 1 foot of freeboard to allow time to apply the pond contents to the land if the weather is inclement when the pond is to be emptied (1 foot from full). Assume the holding pond is designed as an earthen basin to store 180 days of runoff (the Agricultural Engineering Extension computer program AG0003 can be used for the lagoon and holding pond design).
Schematic of an open-lot runoff control/distribution system that uses a pump to convey liquid from the settling basin to the gated-pipe distribution system at the vegetative filter area.
For further information
- USDA-Natural Resources Conservation Service. 1992. Agricultural Waste Management Field Handbook, Part 651. USDA-NRCS, Washington, D.C.
- LPES Lesson 42: Controlling Dust and Odor from Open Lot Livestock Facilities.
- NRAES31 Proceedings from the Dairy Waste Management Symposium, Syracuse, New York, Feb. 22-24, 1989.