Ohio Livestock Manure Management Guide

Bulletin 604-06

Chapter 1—Manure Characteristics

The quantity, composition, and consistency of manure influence the selection and the design of manure-handling facilities. In its strictest definition, animal manure refers only to feces and urine. However, bedding, feed wastage, rain, soil, milk-house wastes or wash, and more are mixed with the feces and urine on many farms. This results in a manure that has properties considerably different from fresh manure. To minimize confusion in this chapter, the term fresh will be added to manure when talking only about feces and urine mixtures.

Fresh Manure

Table 1 lists fresh manure (feces and urine) production and its characteristics by livestock types, weights, and production levels. Values in the table are averages for individual animals being fed according to National Research Council Guidelines (2001). Variations of ±20% can occur and are highly dependent on feed digestibility and nutrient feeding levels of the animal. Recent studies have shown nitrogen (N), phosphorus (P), and potassium (K) can be reduced in many feeding programs without reducing animal productivity. The result is manure with N, P, and K levels lower those given in Table 1. Laboratory analysis of fresh manure is the most reliable way to determine its chemical content. Procedures for sampling manure are discussed at the end of this chapter.

The first part of Table 1 gives the ratio of fresh manure weight generated daily per animal body weight, along with moisture and dry solids level. Also included are ash, N, P, and K concentrations as a percentage of dry solids (all water removed). Results show that manure production per unit of body weight varies with production level (dry vs. lactating), diet (high energy vs. high roughage), sex, age, and stage of production, as well as with species. Also, N, P, and K concentrations vary with these same factors. Thus, the quantity and properties of manure depend on:

• Animal—species, age, productivity.
• Levels of nutrients fed and ration digestibility.

Two properties of fresh manure are relatively constant, namely water content and density. For fresh manure, water content is consistent at 88 to 92% for non-poultry species and 73 to 75% for poultry. Thus, unless an animal is sick or is being fed excessive levels of salt (in which case, moisture increases), these moisture ranges can be expected. Manure in the 88 to 92% range should be handled as a liquid, while manure in the 73 to 75% range should be handled as a solid. Figure 1 shows graphically how manure moisture affects its handling characteristics. Chapter 3 on Manure-Management Systems describes manure-handling systems and the range of manure water contents they will handle.

Figure 1. Physical manure characteristics and handling requirements. (Source: Ohio State University Extension Bulletin 604, 1992 Edition.)

Density of fresh manure is similar for all species at 62 to 65 lb/ft³ (water has a density of 62.4 lb/ft³). At these densities, a gallon of manure would weigh approximately 8.3 lb. Therefore, to convert fresh manure weights to gallons, divide weights by 8.3.

The second part of Table 1 gives the weight and volume of fresh manure, solids, and quantities of N, P₂O₅, and K₂O produced daily per animal type. N, P₂O₅, and K₂O concentrations were calculated by multiplying:

This information can be used to estimate the quantity of total nutrients generated daily per animal on a farm. For example, a dairy cow producing 90 lb milk per day generates daily 153 lbs (18.4 gal.) of fresh manure containing 1.00 lb N, 0.30 lb P₂O₅, and 0.56 lb K₂O.

Table 2 shows the dollar value of nutrients in 1 ton (or 241 gallons) of fresh manure and 1 ton of dry manure at 15% moisture for each animal type. The results show how moisture impacts the value of a ton of manure. For example, a semitruck-load (25 tons) of fresh turkey manure might be worth $481. However, if the manure were dry (15% moisture), it could be worth $1,635 for the same NPK analysis on a dry basis.

Bedding should be considered in many manure-handling systems. An estimate of the amount of bedding used can be obtained by measuring the amount used for a small number of animals and expanding it to the whole herd. Table 3 provides characteristics of common bedding materials as related to water absorption and fertilizer nutrients. This information can be used in calculating nutrient value of fresh manure and the bedding when laboratory analysis is unavailable.

Bedding, water additions, handling and storage losses alter manure’s characteristics; therefore, the data given in Table 1 and Table 2 are only the place to begin for analyzing nutrient loading rates on farms and calculating the value of manure.

Volume of Manure

Estimating the total volume of manure produced is accomplished by adding the volume of fresh manure from the animal, plus half the volume of the dry bedding used, plus the volume of water additions. Only half the volume of bedding is used to allow for void spaces in the bedding which are filled with the fresh manure during mixing.

Moisture and Composition

Figure 2 shows the ratio of bedding to fresh manure needed to achieve a specific moisture ratio of manure. For example, free-stall fresh manure (88% moisture, liquid) would require about 0.05 lb of dry bedding at 10% moisture to be added per 1.0 lb of fresh manure to produce a semi-solid manure with a moisture of 84%. For a dairy cow producing 90 lb of milk per day, this would be about 7.7 lb per day of bedding (153 lb manure per day x 0.05). If the bedding was wheat straw, this would have added 0.038 N, 0.014 P₂O₅, and 0.069 K₂O lbs per day of nutrients or a 3.8%, 4.7%, and 12% increase above fresh manure values, respectively. When bedding with straw or corn stalks, nutrient values should be considered for nutrient management planning (NMP) on a farmstead. However, for sawdust or sand bedding, nutrient additions will generally be less than 3% for N, P₂O₅, and K₂O.

Figure 2. Expected manure moisture based on ratio of bedding added to fresh manure.

Sand Bedding

Sand-bedded dairy free-stall barns have become increasingly popular because of cow comfort and hygienic improvements over organic bedding and mats. Sand usage averaged about 53 lb per stall per day in Michigan State University studies (Michigan State University Extension Bulletin E-2561). The sand significantly increases the solids content of the manure and its volume. However, since sand does not readily absorb water, the manure will continue to behave as a slurry or semi-solid. For details on the amount of bedding required to thicken manure, refer to MidWest Plan Service (MWPS), MWPS-18-S1, Manure Characteristics, available from your local county office of Ohio State University Extension or online at the MidWest Plan Service, www.mwpshq.org/default.htm.

Other materials often get added to fresh manure. Feed wastage and soil can add considerable nutrients, while water additions from washing equipment and buildings, leaking waterers inside buildings, rain from building roofs and outside lots, and rainfall into open storage structures can add considerable volume and weight. Conversely, manure in open lots or well-ventilated buildings will often lose water. Thus, the quantity and the properties of manure depend on:

• Quantity of added bedding, feed wastage, soil, surface water, washwater, etc.
• Environment—wet or dry climate, housing ventilation, handling and storage losses.

Handling and Storage Losses

Nutrient losses occur in the handling, storage, and spreading of manure. The major nutrient lost is nitrogen through volatilization of ammonia and can range as high as 80% or more of the total nitrogen. Also, phosphorus can be lost due to its accumulation in the unrecovered sludge in the storage sys-­tem. Because nutrient losses are highly variable, theinformation on fresh manures and bedding given in Tables 1, 2, and 3 should not be relied upon once manure is available for sampling and analysis. Sampling is also recommended because of uncontrolled water additions or losses (drying) that can occur. Thus, to accurately predict manure properties, sampling and testing manure from storage is critical.

Sampling, Testing, and Evaluating Manure Nutrients

Sampling

To make the most appropriate and environmentally responsible use of manure, it is necessary to test the manure to accurately determine its nutrient concentrations. Furthermore, for the test results to be meaningful, it is important to obtain an adequate number of samples that are representative of the bulk manure. The number of samples needed will depend on the variability of the manure. The more variable the manure, the more samples are required. Variability of liquid manures is usually less than for solid manures, especially if the liquid manure can be mixed prior to sampling.

Manure from different storage systems should be sampled differently. For solid manures, the sample can be taken while loading or during spreading. For poultry, the sample can come from within the house or from a stockpile of litter. Liquid manure can be sampled from storage or during the time of application. Liquid manure in storage should be agitated two to four hours before taking the sample. More details on recommended sampling procedures are given in Appendix A.

Testing: Select a reputable testing laboratory. In selecting a laboratory, determine if the laboratory is knowledgeable in testing manure and belongs to a manure proficiency testing program. Obtain the laboratory’s appropriate sampling kit and read the corresponding instructions thoroughly. Manure samples should be identified regarding the farm, animal species, and date of sampling. The samples should be kept frozen until shipped to a laboratory. It is best to ship early in the week.

The laboratory analyses required on manure are moisture, total nitrogen (N), ammonia-N (NH₃-N), phosphorus (generally reported as phosphate [P₂O₅]), and potassium (generally reported as potash [K₂O]). Other useful analyses include pH, electrical conductivity, calcium (Ca), magnesium (Mg), and sulfur (S). The nutrients manganese (Mn), copper (Cu), and zinc (Zn) may also be important, especially if these nutrients are included in the animal diet.

Evaluation of Test

Most laboratories design their test reports to meet the needs of their customers. However, there may be differences from laboratory to laboratory in the reporting format, reporting units of the test values, conversion factors, and the estimate of the nutrient availability. The test report usually involves three types of information. The first type is the descriptive information about the sample and the customer, including sample identification, sample description, and date of analysis.

The second type of information is the actual analytical results. Careful attention should be paid to the units associated with the test values. Typically, the laboratory will report the test values in parts per million (ppm) or percentage (%), and then convert them to the units needed by the customer to calculate application rates. Examples are lb per 1,000 gal for liquid manure and lb per ton for solid manure. Laboratories may also report the analysis on an as-is basis and a dry-matter basis. The as-is basis is used to calculate the application rates. Most laboratories report the results only on an as-is basis. However, the dry-matter basis, if it is needed, can be calculated from the moisture determination. The dry-matter basis is used to compare the nutrient concentrations of one manure with those of another manure.

The third type of information is interpretive and includes estimates of nutrient availability and fertilizer value. Since the laboratory may be using estimates of nutrient availability from other sources, it is important to verify that the lab’s nutrient availability factors are the same as reported in this bulletin for Ohio conditions. The fertilizer value is often assigned to the manure by taking into account the current local fertilizer prices for the nutrients in the manure. However, the fertilizer value may be less when not all nutrients are needed due to already high soil-test levels. Manure application costs vary between fields and can be more than the fertilizer value of the nutrients. Therefore, the value of manure may be different, depending on the field to which it is applied. More details for reporting manure test results can be found in Appendix B.

Record Keeping

The frequency of testing should be such that a good record of the nutrient concentrations in the manure can be established. It is important to get a feel for the variation in these concentrations over time. With good frequency of testing and record keeping, substantial changes in nutrient concentrations in manure, such as those due to changes in manure storage or animal feed, can be recognized.

Summary

The quantity and properties of manure depend on:

• Animal—species, age, productivity.
• Levels of nutrients fed and ration digestibility.
• Quantity of added bedding, feed wastage, soil, surface water, washwater, etc.
• Environment—wet or dry climate, housing ventilation, handling and storage losses.

Once a manure system is in place, sampling manure from storage is critical to estimate nutrient loading rates on farms and calculate the value of manure accurately.

References

Lawrence, L., J. R. Bicudo, and E. Wheeler. 2003. Horse Manure Characteristics Literature and Database Review. Pp. 277-284. Ninth International Animal, Agricultural, and Food Processing Waste Proceedings. ASAE Publication No. 701P1203, October 12, 2003.

MidWest Plan Service–18, 3rd Edition. Livestock Waste Facilities Handbook, 1993.