Ohio Livestock Manure Management Guide

Bulletin 604-06

Chapter 6—Land Application of Manure

Manure is a valuable resource that needs to be managed effectively and efficiently. Land application of manure should not be considered simply a disposal system. Manure provides nutrients for crops and helps build and maintain soil fertility. Manure can also improve soil tilth, increase water-holding capacity, lessen wind and water erosion, improve aeration, and promote beneficial organisms. There are three principal objectives in applying animal manure to land:

• Ensure maximum utilization of the nutrients in the manure by crops.
• Minimize environmental hazards.
• Minimize neighborhood complaints and concerns.

Available land for manure application is an important consideration for all livestock operations. When planning a new operation or expanding an existing operation, adequate land area for manure application must be included in the plan. A conservative approach in determining the amount of land required is to consider the removal of the nutrient by the harvested crop. This will ensure that enough land area is available in future years to prevent nutrient buildup in the soil beyond recommended agronomic and environmental levels.

The whole farm nutrient management procedures described in Chapter 2, Whole Farm Nutrient Budget/Planning, provide guidelines for balancing nutrient inputs and outputs on the farm. In addition to balancing nutrients, best management practices (BMPs) for applying manure to crops must be used. To maximize manure nutrients while minimizing potential environmental impacts and neighbor’s concerns, manure application must consider nutrient losses during handling and storage, runoff and preferential flow, and timing and rate of application.

Nutrient Losses During Handling and Storage

Nitrogen (N) is the nutrient most likely to be lost during handling and storage of manure. Table 13 provides a comparison of N losses due to storage and handling. The systems are described in Chapter 3, Manure-Management Systems. Nitrogen lost to the atmosphere through volatilization can be reduced by applying manure when soil and air temperatures are less than 50ºF and by incorporating manure into the soil within 24 hours of application. The amount of N available from the manure also depends on the method of application. Injecting, chiseling, or knifing liquid manure into the soil minimizes odors and nutrient losses to the air or as surface runoff.

Additional issues need to be considered when applying liquid manure and wastewater. To minimize the risk of runoff or preferential flow (see following section), site inspection and preparation are important. In addition, hourly application rates must be controlled as discussed later in this chapter. Appendix E, Liquid Manure Application, provides management guidelines and information on equipment needs.

The use of manure or wastewater for “true” irrigation is seldom accomplished because of the relatively small volumes applied and annual application-rate restrictions. Those who desire to irrigate in addition to spreading manure must be certain of an adequate supply of water available for irrigating. Liquid manure from below-ground storage, earth basins, or above-ground storage should not be used to irrigate growing crops as the manure is usually high in ammonia and solids, which can coat and/or burn vegetation. However, wastewater in the second stage of a two-stage lagoon may be dilute enough for irrigation on growing crops.

Advantages of Irrigating with Liquid Manure

• Large amounts of effluent can be spread in a relatively short time.
• Waste effluent can be used to supplement irrigation water and to supply plant nutrients where regular crop irrigation is practical.
• Irrigation may cost less than other land-application methods to install, usually is cheaper to operate, and requires less labor for equivalent volumes of application.
• A high degree of automation is possible with some types of irrigation equipment.
• Manure guns (nozzles) can handle slurry directly from confinement and wash-down operations.
• Disposal can often be accomplished when moist soil conditions prohibit conventional hauling. However, do not irrigate on saturated soil, as runoff will occur. (See Appendix F, Available Water Capacity, for more information.)
• Less soil compaction occurs with irrigation than with tank wagons.

Disadvantages of Irrigating with Liquid Manure

• An adequate application area may not be within economical pumping distance of the waste source.
• Odors and spray drift (aerosols) are possible, depending on location and management.
• Additional water supply and/or large storage basins may be required for dilution, flushing the equipment, and safe efficient use of wastewater.
• Runoff is a potential pollution hazard. (See Appendix F, Available Water Capacity, for more information.)
• Without good management, annual application of nutrients may be excessive and cause nitrate pollution in ground water. Operator error or mismanagement is often a cause of liquid manure flowing through subsurface drains to surface waters of the state.
• Over-application or a too-high application rate may result in irrigated wastewaters entering the drainage tile and surface water supplies. See section on Preferential Flow in this chapter for best management practices to prevent liquid manure in subsurface drains.

Runoff and Preferential Flow

Excess nutrients in soil may impact the environment when they are dissolved or eroded and transported to surface or ground water supplies. Excess phosphorus (P) in surface waters can result in eutrophication and a decrease in oxygen levels in the water that leads to loss of animal life. Nitrogen compounds may harm human health and are toxic to fish. In addition, erosion of manure may contaminate water supplies with pathogens such as E. coli or Cryptosporidium. Minimizing these environmental risks requires using best management practices when applying manure to cropland.

While most transport of P occurs with the erosion of soil sediment, it can also leach if soil P levels are too high. Phosphorus accumulates in soils if applied in quantities greater than those removed by crops. Accumulation of P in the soil can be measured by soil-testing.

To minimize potential N runoff, manure applications should not provide more available N than what is needed by the succeeding crop. For corn, the determination of total available N should include credits for any contributions of the present or preceding crop, any N fertilizer added, and available N provided by previous manure applications. The Tri-State Fertilizer Recommendations (contact Ohio State University Extension or see ohioline.osu.edu/e2567) provide recommendations for corn, soybeans, wheat, and alfalfa for N-P-K fertilizer.

Minimizing Runoff

Runoff potential is affected by numerous factors, some of which are fixed by the nature and location of the field, while other factors can be altered through management. Runoff potential must be determined on a site-by-site basis by evaluating:

1. Location of receiving stream. Runoff to streams is more likely when the field selected for manure application is bordered by a stream or other surface water rather than separated from surface water by a field, pasture, wooded area, or other suitable buffer strip.
2. Slope steepness and complexity. Runoff is more likely from fields sloping steeply and evenly toward a stream than fields with a gentle or no slope. Priority areas for land application of manure should be on gentle slopes located as far as possible from waterways. When manure is applied on more steeply sloping land or land adjacent to waterways, other conservation practices should be installed to reduce runoff potential.
3. Soil and weather conditions. Runoff is more likely when applied on frozen, saturated, or compacted soils.
4. Soil type. Soils with low infiltration rates and/or soils with limited water-holding capacity are more likely to promote runoff than soil types that absorb and retain large quantities of water.

Management factors that can alter the potential for manure runoff into a stream include:

1. Buffer strips. Properly designed buffer strips along stream banks adjacent to sites with high-runoff potential can absorb the runoff, reducing the amount of manure entering a stream.
2. Soil surface condition. A rough or covered soil surface reduces runoff compared with soil surfaces that are smooth or have very little residue cover.
3. Manure characteristics, application rate, and application method. Liquid manure applied at rates greater than the soil infiltration rate or water-holding capacity can promote runoff. Injection or incorporation of applied manure reduces chances of runoff. (See Chapter 5, Farmstead Runoff Control.)
4. Pre-existing nutrient status of the soil. Greater quantities of nutrients are likely to move off fields when soils have a high soil test level rather than lower soil test levels.
5. Surface and subsurface drainage. Proper installation and routine maintenance of surface and subsurface drainage systems can reduce the potential for runoff or direct discharge of manure from land application.
6. Setback distances. To protect the environment and minimize neighbor complaint, manure should not be applied adjacent to sensitive areas. Table 15 specifies these minimum setback distances. Consider additional application setback distances from neighbors and environmentally sensitive areas such as sinkholes, wells, gullies, ditches, surface inlets, or rapidly permeable soil areas. Setback distances may need to be increased due to local conditions such as a pond or lake used for a water supply or recreational area or a stream that is already impaired by excess nutrients.

1. Avoid applying manure before or after a heavy rain. Monitor manure storage capacity to prevent applying when conditions are not acceptable. Applicators have a limited number of days to apply manure when environmental conditions (soil, wind, rain, moisture) are optimal, so it is advisable to contact custom applicators up to a year in advance of the anticipated manure application. Use crop rotations that will allow timely manure applications throughout the growing season.
2. Reduce liquid manure application rates. No more than 13,000 gallons or 0.5 inch of liquid manure per acre should be applied in one application. Multiple smaller applications of 7,000 gallons or 0.25 inch of liquid manure per acre allow for more effective absorption by the soil than one large single application. Reduce manure application rates if wet soil conditions exist. Do not apply a greater volume (gallons per acre) than the upper eight inches of soil can hold. See Appendix F, Available Water Capacity.
3. Maintain subsurface drainage lines and drainage outlets. Do not apply liquid manure if subsurface (tile) lines are flowing with water. In areas with springs, subsurface lines flow continually, and soil moisture conditions should determine application. (See Appendix F, Available Water Capacity.) Monitor drainage outlets before, during, and after manure applications for signs of discharge. If manure is in the tile flow, plug the outlets or capture the flow immediately. Provisions for tile plugging or the capture of tile flow must be planned and available prior to application. Follow emergency manure spill procedures if a spill occurs.
4. Minimize preferential flow by tilling the soil at least three to five inches when large macropores like cracks, earthworm burrows, or root channels exist. If manure is injected, use straight points spaced closely to reduce the volume of liquid manure coming out of each knife point. For soils with “cracks” more than six- to eight-inches deep at the time of application, till before application or do not apply until adequate moisture seals the cracks.
5. Calibrate manure application equipment before application. Over application of liquid manure is a major cause of liquid manure in surface water.
6. Maintain minimum setback distances from surface water. See Table 15, Minimum Recommended Setback Distances from Sensitive Areas. Minimum suggested setback distances vary depending on weather, soil conditions, and time of year. For winter manure application, setback distances are doubled.
7. Install in-line tile flow controls that can plug tile flow or have inflatable tile plugs available during application. Control structures allow for easy monitoring and cleanup of manure in tile lines but need to be installed properly to prevent leaching around the control structure. Allow enough time for the liquid manure and surface water to absorb into the surrounding soil before removing the plug.

Record keeping is important in preventing manure in subsurface (tile) lines. Document application rates, set-back distances, weather and soil conditions, subsurface drain lines and outlets, broken tile, sink holes, and other potential problems to help prevent environmental problems in the future. Have emergency equipment (backhoe, bales of straw, pumps, etc.) available if a liquid manure spill occurs. See Chapter 7, Safety and Manure Handling.

Rate and Timing of Application

Source: USDA-Natural Resources Conservation Service (NRCS), Ohio Field Office Technical Guide, Section IV, Standard 633. Used by permission.

Using best management practices to determine the rate and timing of manure application will optimize crop production, reduce environmental risks, and minimize neighbors’ concerns. The factors that most often limit the amount of manure that should be applied to cropland are existing soil-fertility levels, manure nutrient content and concentration, crop nutrient needs, runoff potential, slope, leaching potential, and site limitations. Hauling distances, distance to surface water, distance to neighbors, distance to water wells, the potential for manure leaching to tile lines, and other factors can also limit how and when manure is applied.

Assessing Nutrient Needs

Manure application rates must balance manure nutrients with crop nutrient requirements as discussed in Chapter 2, Whole Farm Nutrient Budget/Planning. In general, only about one-third of the organic nitrogen in animal manure is available to crops during the year it is applied, and the remaining two-thirds, residual organic nitrogen, becomes part of the soil organic matter over time (Table 16). Phosphorus and potassium from manure application are considered as available as commercial fertilizer during the first growing season. The limiting nutrient, usually nitrogen (N), phosphorus (P), or potassium (K), will determine the amount of manure applied. The limits on the amount of phosphorus that can be applied are those that most often limit any further manure applications. Since it is difficult to balance manure nutrients, additional fertilizer applications may be needed to balance the crop’s nutrient needs.

Other limitations to manure application include volume limitations relating to how much manure can physically be applied to the soil at one time. With low nutrient concentrations in liquid manure, large volumes of liquids may be applied and yet the crop nutrient needs may not be met simply because the liquid is mostly water and has low concentrations of nutrients. Application of liquid manure above the available water capacity of the soil can create a runoff risk and leaching to tile or underground water (See Appendix F, Available Water Capacity.) Manure application equipment on wet soils can cause significant soil compaction.

Application Rate Considerations for Liquid Manure and Wastewater

To prevent runoff or preferential flow, hourly application rate should be matched to the infiltration rate and permeability of the soil. The design application rate should be conservative and usually lower than the maximum allowable rate in the Ohio Irrigation Guide, because the soil intake rate may be reduced over time by the solids and salt content in some wastes. When recommended application rates vary with soil depth, use the value at eight inches of depth, which is less than that at the surface.

Limit the one-time application volume to an amount that will bring the soil to field moisture capacity. (See Appendix F, Available Water Capacity.) Limit application rates to the water-holding capacity of the top eight inches of the soil profile. The amount applied must not exceed the holding capacity of the soil at the time of application. Inspect fields for broken tiles and other possible short-circuit routes that could result in a direct discharge of manure to drainage tile and surface-drainage ditches. If rapid infiltration to subsurface drainage tile is a problem, consider light disking, shallow chisel plowing, or other tillage operations before irrigating manure and wastewater to improve the soil’s infiltration and holding capacity. Lower application rates and multiple passes with irrigation equipment may also be necessary.

Timing of Application

Source: USDA-Natural Resources Conservation Service (NRCS), Ohio Field Office Technical Guide, Section IV, Standard 633. Used by permission.

Crop rotation and seasonal variations affect when manure should be applied. In a corn-soybean rotation, the fall, after the crops are harvested, is the best time to apply manure. Generally, the fall has drier weather so compaction problems can be minimized. Fieldwork can also be accomplished in the fall to incorporate the manure. Sometimes manure can be applied in the spring if weather conditions and time permit. Usually, manure cannot be applied during the growing season, although some liquid systems may permit side-dress applications of manure to corn.

If wheat or oats are in the rotation, the manure can be applied in the late summer months. For wheat or oats, winter and spring applications of manure to the growing crop are not recommended. Forage crops (grasses and legumes) are capable of using more nutrients than row crops (corn, soybeans, and wheat).

A planned grazing system can substantially reduce the manure that must be handled and applied and can reduce costs and environmental hazards. Manure can be applied to hay or pasture land but smaller applications are need to preserve forage quality and to limit crop damage. It is preferable to apply manure on pastures and hayland soon after cutting or grazing before re-growth has occurred. Also, limit the application rate to avoid salt damage and/or coverage to the pasture and hayland. Table 18 provides general guidelines for timing manure application.

1. Application rate is limited to 10 wet tons per acre for solid manure with more than 50% moisture and five wet tons for manure with less than 50% moisture. For liquid manure, the application rate is limited to 5,000 gallons per acre.
2. Applications are to be made on land with at least 90% surface residue (e.g., good quality [grass] hay or pasture field, all corn grain residue remaining after harvest, all wheat residue cover remaining after harvest).
3. Manure should not be applied on more than 20 contiguous acres. Contiguous areas for application are to be separated by a break of at least 200 feet. Utilize areas for winter manure application that are the farthest from streams, ditches, waterways, and surface water and use areas that present the least runoff potential.
4. Increase the application setback distance to 200 feet minimum from all grassed waterways, surface drainage ditches, streams, surface inlets, and water bodies. Minimum suggested setback distances are doubled for winter application of manure to frozen or snow-covered soils. See Table 15, Minimum Recommended Setback Distances from Sensitive Areas. This distance may need to be further increased due to local conditions.
5. Additional winter application criteria for fields with significant slopes of more than 6%. Manure should be applied in alternating strips 60 to 200 feet wide generally on the contour, or in the case of contour strips on the alternating strips.

Application of Manure on Steep Slopes

Source: USDA-Natural Resources Conservation Service (NRCS), Ohio Field Office Technical Guide, Section IV, Standard 633. Used by permission.

Manure should not to be applied to cropland with slopes of more than 15% or to pastures/hayland with slopes of more than 20% unless one of the following precautions is taken:

1. Immediate incorporation or injection with operations done on the contour, UNLESS the field has 80% ground cover (residue and/or canopy).
2. Applications are timed during periods of lower runoff and/or rainfall (late May to mid-October).
3. Lower rates can be applied by using split applications (separated by rainfall events). Apply no more than 10 wet tons/acre for solid manure, or 5,000 gallons/acre for liquid manure.
4. The field is established and managed in contour strips with alternate strips in grass or legume.

Timing of manure application should also consider the potential impact on neighbors. To develop and maintain good neighbor relations, give adequate notice of the intent to land-apply manure and do not haul and spread on weekends, holidays, or important events. Good communication is key to minimizing neighbor’s complaints.

Manure Application Record Keeping

Keep good field records of soil and manure test results, yields achieved, and nutrients applied (time, form, rate, and method of application). Records should be kept for a period of five years or longer (metals analyses and associated application rates and locations should be maintained permanently):

• Quantity of manure produced and its appropriate analysis.
• The last three soil-test results.
• Dates, analysis, and amounts of manure that are land-applied.
• The dates and amounts of manure removed from the system due to feeding, energy production, or export from the operation.
• Manure application methods.
• Crops grown and yields (both yield goals and measured yield).
• Other tests, such as determining the nutrient content of the harvested product.
• Calibration of application equipment. See Appendix H.
• Soil moisture and weather conditions (temperature and wind direction) at the time of application.
• Consider annual reviews to determine if changes in the nutrient budget are desirable (or needed) for the next planned crop.