Charles D. Fulhage and Donald L. Pfost
Agricultural Engineering Extension

Donald L. Schuster
Natural Resources Conservation Service

Many livestock and poultry producers fall into one of three categories:

  • They are willing to make high capital and labor outlays to maximize the use of their manure for crop production;
  • They are willing to minimize the amount of nutrients returned to the land for crop production in exchange for a relatively low-cost and low-labor method of manure handling;
  • They have insufficient acreage to make use of the nutrients in their manure and depend on neighbors to accept or buy all or a portion of their manure.

Producers in the first category usually use slurry systems with tanks for manure storage, and tank wagons with injectors (or drag-hose systems) to transport and apply the manure. Producers in the second category use lagoons for storage/treatment, and irrigation equipment to transport and apply the manure to their fields. Producers in the third category may use their equipment to apply manure on neighbors' land or they may sell their manure through a broker.

To have value, manure nutrients must be used in a manner that results in a salable product. This publication describes methods of recovering a portion of the plant nutrient value of animal manure.

To keep the addition of nutrients from manure and fertilizer in balance with the nutrient removal by crops requires a record-keeping system that includes soil tests, laboratory analysis of the manure nutrient content, manure application rates, and crop yields. To obtain reliable nutrient data, it is necessary that the manure be well mixed before and during the loading, sampling, transport and land application processes.

Fresh manure nutrient production

Typical nutrient production values for various species and weights of animals are listed in Table 1 PDF for fresh manure that has not been treated or altered.

Example calculation of manure volume produced
Find the volume of manure that must be hauled annually from 100 head of 1,400-pounds lactating dairy cows (not including any wash water, rainwater or evaporation) using the manure production value from Table 1 PDF.

2.4 (cubic feet per day) per head x 100 head x 365 days = 87,600 cubic feet= 655,000 gallons = 131 loads at 5,000 gallons per load

Table 2 PDF lists the daily production of the major nutrients in pounds per day for swine manure in deep-pit buildings and the volume of manure produced daily.

Example calculation of manure volume produced
Find the required deep-pit volume to contain the manure produced in six months by 1,000 head of grow-finish swine with an average weight of 150 pounds using dry feeders as follows (refer to Table 2 PDF):

0.16 (cubic feet per day) per head x 1,000 head x 183 days = 29,280 cubic feet = 218,865 gallons

In calculating pit depth required, make allowance for clearance under the floor for any pit ventilation and for gas accumulation.

Table 3 PDF lists the annual production of the major nutrients in pounds per year for liquid pit manure from various animals and the weight of manure produced annually. The concentration of nutrients per 1,000 gallons is also listed.

Example calculation of manure volume produced
Find the value of the P2O5 in a 5,000 gallon load of liquid pit manure produced by mature dairy cows (refer to Table 3 PDF and assume $0.26 per pound for P2O5 applied in the liquid manure):

15 pounds P2O5 per K-gallons x 5 K-gallons x $0.26 per pound = $19.50 (K-gallons = 1,000 gallons)

This calculation assumes that a soil test indicates phosphate is needed. If phosphate level in the soil is already high, the P2O5 applied in the liquid manure may have a negative value, which should be deducted from the value of the N and K2O in the manure. Missouri policy recommends that intense phosphorus nutrient management be considered when soil test phosphorus levels are rated high or greater.

Table 4 PDF shows estimated lagoon nutrient accumulations for various animals. Nutrient concentrations in all properly operating lagoons are very low because of the high volume of dilution water, nutrient settling and ammonia volatilization. Lagoon effluent nutrient characteristics for different animal species (e.g., swine, beef, dairy and sheep) are similar. Using an estimated nutrient concentration of 4-2-3 pounds (N-P2O5-K2O) per 1,000 gallons will be representative of many lagoons. About 80 to 90 percent of nitrogen in well-seasoned, steady-state anaerobic lagoons is in the ammonia form and is subject to high losses from volatilization when land applied without incorporation.

Example calculation of manure volume produced
Find the value of the K2O in the lagoon effluent produced annually from a 1,000-head grow-finish unit (refer to Table 4 PDF and assume $0.16 per pound for K2O applied in the lagoon effluent):

3 pounds K2O per pig space-year x 1,000 pig spaces x $0.16 per pound = $480.00

This calculation assumes that a soil test indicates potash is needed.

Example calculation of the annual volume of effluent from a 100-cow milking parlor and milkhouse plus the manure and flush water from the holding area assuming the average cow weight is 1,400 pounds each (reference Table 5 PDF)

1.6 cubic feet per day x 100 cows x 1400 pounds per 1000 pounds x 365 days per year = 81,760 cubic feet = 611,565 gallons

Table 6 PDF lists the percent of original nutrient content of manure retained by various manure management systems.

Example calculation of manure volume produced
Find the average gross value of the K2O retained in the manure from 200 head of 1,100 pounds beef feeders fed a high-energy ration in an open lot (in a cool, humid region) for 180 days (refer to Table 1 PDF for the daily K2O production and to Table 6 PDF for the average percent of original manure nutrient content retained and assume $0.16 per pound for K2O in the manure to be land applied):

0.32 pound K2O per animal-day x 200 animals @1100 pounds x 180 days x 0.625 retained x $0.16 per pound = $1152.00

This calculation assumes that a soil test indicates potash is needed.

Table 7 PDF lists some of the important characteristics of beef manure from open feedlots in an arid region.

Example calculation of the weight of manure produced
Find the weight of manure to be hauled per year from 200 head of 1,000 pounds beef feeders fed in an unsurfaced lot in a dry climate:

9.60 pounds per animal-day x 200 animals @1000 pounds x 365 days per 2,000 pounds per ton = 350.4 tons = 70 five-ton loads

Table 8 PDF lists some of the important characteristics of beef feedlot runoff stored in a pond.

Example calculation of the value of the ammonia nitrogen (NH3-N) per acre-inch of effluent from a beef feedlot runoff pond
(Assume that 25 percent of the ammonia nitrogen (NH3-N) will be lost (volatilized) during land application by sprinkler irrigation (from Table 13 PDF), one acre-inch = 27,153 gallons, and a value of $0.26 per pound of N).

1.50 pounds per K-gallon x 27.153 K-gallons x 0.75 retained x $0.26 per pound of N = $7.94 per acre-inch

Table 9 PDF lists typical ranges of nutrient contents of anaerobic lagoon systems. Climatic effects such as rainfall and runoff from open lots can significantly affect the concentration of nutrients in lagoons. Additionally, some nutrients are concentrated in the sludge layer and may not be available if the lagoon is not agitated.

Example calculation of the average value of the ammonia nitrogen (NH3-N) per acre-inch of effluent from an anaerobic beef lagoon
(Use the ammonia N content from Table 9a PDF, assume that 25 percent of the ammonia nitrogen (NH3-N) will be lost (volatilized) during land application by sprinkler irrigation (from Table 13 PDF), and a value of $0.26 per pound of N.)

50 pounds of (NH3-N) per acre-inch x 0.75 retained x $0.26 per pound of N = $9.75 per acre-inch

Table 10 PDF lists typical nutrient concentrations in various types of solid manure. Solid manure usually contains the manure as it is excreted by the animal and may be mixed with considerable bedding. Most of the phosphorous and potassium excreted by the animal is usually contained in the manure hauled to the field.

Example calculation of the average value of the total Kjeldahl N per wet ton of poultry litter
(Use the total Kjeldahl nitrogen content from Table 10 PDF, assume that 22.5 percent of the nitrogen will be lost (volatilized) from land application on fescue pasture without incorporation (from Table 13 PDF), and a value of $0.26 per pound of N.

60 pounds of N per ton x 0.775 retained x $0.26 per pound of N = $12.09 per ton

Table 11 PDF lists typical ranges of nutrient concentrations in slurry manure. Slurry manure is relatively concentrated, especially if the manure is from a covered pit and contains no rainwater. Slurry manure usually contains 5 to 10 percent solids and can be handled as a liquid with manure pumps and tank wagons.

Example calculation of the gallons of swine slurry manure required to knife-in (inject) 200 pounds (net after application loss) of total Kjeldahl N per acre for corn production
(Use the average total Kjeldahl nitrogen content at 52.5 pounds per K-gallon from Table 11 PDF and assume a 5 percent nitrogen loss (from Table 13 PDF)).

200 pounds N per K-gallon/(52.5 pounds of N per K-gallon x 0.95) = 4.01 K-gallons = 4,010 gallons

Nutrient losses and availability

Losses in nutrient value are inherent in any system of manure management, both during the collection and storage phase and the land application phase, especially nitrogen losses due to volatilization and denitrification. In the collection and storage phase, nitrogen can be lost to the air as ammonia and from manure stored in open lots by leaching and runoff, additionally. Table 14 PDF lists typical nutrient losses incurred with some common systems of manure handling and storage. About 20 to 40 percent of the phosphorous and 30 to 50 percent of the potassium can be lost by leaching and runoff from open lots. Thus, to minimize nutrient losses as well as to reduce pollution problems from rainfall runoff, all operations (feeding, loafing, manure storage, etc.) should be kept under roofs — not in open lots. Phosphorous in lagoons tends to settle out of the liquid and concentrate in the sludge layer. Research at MU suggests that as little as 5 to 10 percent of the excreted phosphorous may be pumped from unagitated lagoons using normal pumpdown procedures. Most of the remaining phosphorous will remain in the sludge layer. Potassium is soluble and evenly distributed in the liquid portion of the lagoon. Lagoons normally only have 20 to 30 percent of their volume pumped, depending on the ratio of treatment volume to total volume. A large amount of the potassium may remain in the treatment volume. Research at MU suggests that as little as 15 to 30 percent of the excreted potassium may be pumped from unagitated lagoons.

Frequently, total nitrogen (N) in lagoon effluent is composed of 80 to 90 percent ammonium nitrogen and 10 to 20 percent organic nitrogen. The ammonium nitrogen is equivalent to nitrogen fertilizer and, except for losses to the air, is available to plants in the year of application. The amount of ammonia nitrogen lost to the atmosphere as a gas is difficult to predict because the process depends on many factors such as soil and atmospheric temperature, wind and humidity conditions at the time of spreading, application method and timing of application relative to the nitrogen uptake period (growing season). To minimize volatilization losses of the ammonia nitrogen, manure should be incorporated as soon as possible after surface application. Manure applied to cool, wet soil does not dry readily and thus does not volatilize for several days. Manure applied to hot, dry soil dries quickly and loses most of the ammonia fraction within 24 hours, particularly if there is a hot, dry wind. Dried manure, such as that from a feedlot in an arid or semiarid climate, has already lost much of its ammonia nitrogen and there is little additional loss with time until incorporation. Lagoon effluent applied by irrigation is assumes to be incorporated as soon as it enters the soil. Published values for plant-available ammonia nitrogen from surface-applied manure range from 20 to 80 percent. If manure is a significant part of a crop fertility program, the farmer must consider the possible need for supplemental application of commercial fertilizer nitrogen in the event that plant-available nitrogen is in the lower end of the range noted above. The Missouri Department of Natural Resources (Missouri DNR) requires that a value of 60 percent (40 percent loss) be used in estimating plant-available (surface-applied, no incorporation) ammonia nitrogen unless supporting data or procedures suggest otherwise.

Organic nitrogen must be mineralized (converted to the ammonium form by soil bacteria) before it is available to plants. The rate at which this conversion takes place depends on several factors such as manure type, soil moisture, temperature and pH. Published values suggest that 20 to 90 percent of the organic nitrogen in manure may be converted to plant-available forms during the year in which it is applied. After several years of uniform application (usually about 3 years or more), the nitrogen available from the organic portion of applied manure will tend to stabilize. The Missouri DNR requires that a value of 45 to 62 percent (depending on manure type) be used in estimating cumulative availability of organic nitrogen unless supporting data or procedures suggest otherwise.

Most volatilization (ammonia) losses occur within the first 24 hours after land application, if the waste is not incorporated. Manure spread on the surface and not worked into the soil may lose most of the volatile nitrogen compounds such as ammonia gas to the atmosphere. This lost nitrogen is not available for plant growth. The rate of loss increases with increasing temperature and is greater during dry, warm, windy days than during humid or cold days. Thus, ammonia loss is generally greater during late spring, summer and early fall.

Table 13 PDF shows the decrease in plant-available nitrogen as incorporation is delayed.

Example calculation of the average gross value of the annual nitrogen production from 10,000 laying hens averaging 4 pounds per bird if the deep pit manure is incorporated 4 days after land application
(Use the N value from Table 1 PDF, the deep pit handling and storage loss from Table 12 PDF, the land application loss for wet and warm conditions from Table 13 PDF, and a value of $0.26 per pound of N.)

0.0035 pound of N per bird-day x 10,000 birds x 365 days per year x 0.625 after handling and storage x 0.80 after land application loss x $0.26 per pound of N = $1660.75 per year

Nitrogen applied in excess of crop needs can leach through the soil after conversion to the nitrate form and cause groundwater contamination. Manure should not be applied on snow or frozen soil due to the potential for nutrient removal by runoff and resulting surface water pollution. Once incorporated into the soil, phosphorous and potassium are bound to soil particles such that the principal mode of loss is by soil erosion.

Solid and liquid manure should be plowed down or otherwise incorporated into the soil as soon as possible after land application to minimize odors and volatilization of nitrogen. Lagoon effluent applied by irrigation to soil dry enough to "take water" is assumed to be immediately incorporated, but some volatilization losses do occur with sprinkler irrigation. Although incorporating manure is an effective manure management tool, the vulnerability of the soil to increased erosion risks and other environmental considerations should be evaluated. Additionally, when soil test phosphorus is very high to excessively high, any phosphorus applied may increase leaching and surface runoff.

Table 14 PDF compares typical nitrogen losses for solid, liquid (slurry), and lagoon systems during handling and storage. Losses are highly variable because of seasonal temperature, moisture, climatic and other factors.

Solid manure systems

In the future, it is likely that only poultry operations, smaller livestock operations and open-lot beef feeding operations will be handling manure as a solid. To handle dairy manure as a solid, one practice is to add about 4 pounds of dry straw per cow per day to reduce the moisture content of fresh manure and allow it to be handled as a solid. When this manure is applied to the land, all available nitrogen may be "tied up" by soil microorganisms during the process of decaying the straw. If the decaying process takes place during crop production time, a nitrogen allowance should be made for the decay process, in addition to the nitrogen required for crop production. A second and common practice employed to allow manure to be handled as a solid is to store semisolid manure and allow the liquids to drain off to a holding pond. The liquid is frequently drained through a "picket fence" dam.

Table 15 PDF lists the minimum recommended bedding requirements for various housing systems.

Liquid manure systems

Liquid systems (also called slurry systems) offer greater use of nutrients, if maximizing nutrient use is the goal. Therefore, liquid systems require the maximum soil-plant filter acreage for land application. Storage losses with a manure slurry are lower than with solids or lagoons, especially if stored in aboveground tanks (Table 14 PDF). Knifing liquid into the soil minimizes application losses (Table 13 PDF). The addition of nitrification inhibitors to the manure can slow the conversion of ammonium nitrogen to nitrate nitrogen by certain soil bacteria, thus reducing nitrogen losses by leaching and denitrification. This is the system of choice for operators wishing to make the greatest use of the plant nutrients in their manure.

Lagoon systems

This is the system of choice for producers wanting to minimize one or more of the following:

  • Rrequired soil-plant filter acreage
  • Labor costs
  • Capital investment.

Manure management systems employing lagoons for long-term storage are the least efficient in respect to nutrient use (Table 14 PDF). Losses of up to 90 percent of the nitrogen during storage may occur. Up to 80 percent of the phosphate may remain in the lagoon bottom sludge if the lagoon is not properly agitated when pumped. Land application from lagoons by means of pipes, pumps and sprinkler irrigation is efficient in time and cost; however, without further mechanical incorporation, volatilization losses can be substantial (Table 13 PDF).

Publication No. EQ351