Manure Characteristics Manure Management Systems Series MWPS-18 Section 1 SECOND EDITION Manure Characteristics Jeff Lorimor, Associate Professor, Extension Agricultural Engineer, and Wendy Powers, Assistant Professor, Animal Science, Iowa State University, Ames, Iowa, Al Sutton, Professor, Animal Science Purdue University, West Lafayette, Indiana Manure is a valuable source of nutrients for crops and can improve soil productivity. Manure properties depend on several factors: animal species; diet, digestibility, protein and fiber content; and animal age, housing, environment, and stage of production. Manure is characterized in several ways. Important properties for manure collection, storage, handling and utilization include the solids content (the percent of solids per unit of liquid) and the size and makeup of manure solids (fixed and volatile solids, suspended solids, and dissolved solids). Nutrient content, primarily nitrogen, phosphorus, and potassium, is important as it affects land application rates and treatment techniques. CONTENTS Manure components can be characterized as organic and inorganic. To help Handling Characteristics 2 control disease and parasites, human wastes should not be mixed with animal Liquid 3 manures. Slurry 3 Semi-solid 3 Handling Characteristics Solid 4 The quantity, composition, and consistency of manure greatly influence Sampling and Testing livestock manure facility design. The handling characteristics of manure Manure 4 vary, depending primarily on the amount and type of solids present, Figure 1. Selecting a Testing Laboratory 4 The boundary between handling classifications is not fixed, but varies with Obtaining a Sample 4 specific composition. Manure can be classified, in general, based on how Laboratory Tests 9 manure must be handled. On-Farm Tests 10 Manure handling characteristics vary as consistency changes from liquid Using Test Results 10 to solid. On one end of the spectrum is lagoon liquid with a very low solids Manure Composition 11 content (less than 1%) that can be handled using conventional centrifugal Common Manure pumps. Lagoon liquid can be irrigated using either big guns or center pivot Composition 12 irrigation systems with small nozzles. On the other end of the spectrum is Nutritional Factors Influencing Manure solid manure that must be handled with front-end loaders and/or pitchforks. Composition 19 Solid manure normally has more than 20% solids. In between are the more difficult to handle manures, the ones containing from 5 to 20% solids. The Summary 20 moisture content of the manure is the main determining characteristic, Conversions 20 although solids size, and the presence of bedding also can influence the Worksheet 21 equipment needed for handling, treating, and transporting. Solids generally 22 Manure Management Systems Series tend to settle, but very thick manures (more than Properly designed and managed anaerobic (or 10% solids) hinder settling, and may result in a more aerobic) lagoon treatment systems should have less uniform manure than a settled, thinner one. Sand is than 1% solids, typically from 0.1 to 0.5%. How- another challenging solid that’s sometimes used as ever, it’s not uncommon for overloaded lagoons to dairy bedding. Sand requires special settling and reach as high as 2% solids. handling procedures due to its high density and abrasiveness. Slurry Nutrient values are related to solids concentra- Manure with 4 to 10% solids content can be tions. In general the higher the solids concentration, handled as a slurry, but may require special pumps. the higher the nutrient concentration. Estimates are Swine pit manure typically contains between 2 and available for most manure types, but to really know 6% solids. Deep pit manure will be toward the up- what manure contains, representative samples must per end of the range, while manure in outside pits be analyzed. Estimates and tabular values must be will be more liquid. Outside pits may be either con- used with caution. They are useful for planning pur- crete, steel, or earthen. When wet-dry feeders or swing- poses, but once a facility is established, the best way ing waterers are used, the animals waste less water so to determine nutrient and handling characteristics solids content may increase to 8 to 12%, resulting in is to obtain good representative samples and have a thicker slurry. Dairy manure with milking parlor them analyzed. washwater added typically is handled as slurry. Liquid Semi-solid Manure with up to 4% solids content can be In the 10 to 20% solids content range, handling handled as a liquid with irrigation equipment. Liq- characteristics vary by the type of solids present. In uids that have had the larger solids removed, or ma- this range, the percent solids content does not have as nure with dilution water added may contain 4% or much effect on handling characteristics as does the less solids. type of manure and the amount of bedding present. As excreted Swine As excreted Poultry As excreted Beef (feeders) As excreted Dairy cows 0 5 10 15 20 25 30 Percent total solids (wet basis) Liquid Slurry Semi-solid Solid Figure 1. Relative handling characteristics of different types of manure for various species. NOTE: “As excreted” lines represent the common solids content of manure excreted from a healthy animal. Manure Characteristics 3 This range of solids can be very difficult to choose a laboratory with at least two years of handle and is typical of many dairy operations. The experience in manure testing. manure is too thick to pump, and too thin to scoop. • After the lab receives samples how does it Producers with this thick slurry type of manure may handle those samples? Samples should be have to add water to handle the manure as a liquid, tested immediately or should be refrigerated and will need special pumps to agitate and move the or treated for later testing. manure. Usually, handling the manure with a front- • Is the lab certified by any quality control end loader doesn’t work well because the liquid runs organizations? Having tests done by a lab around the bucket during forward movement. Trans- that meets quality control standards can fer equipment, such as augers and flight elevators, is help validate results. sometimes used. Mechanical scrapers or skid loaders • How long does a customer typically wait with tires attached to the bucket also can be used for before results are returned? Be sure you will manure collection. be able to receive your test results when you need them. Solid Manure, not using sand bedding, with 20% When testing manure for the first time, con- solids content (80% moisture content) or more can sider sending samples to multiple (at least three) be handled as a solid. It can be stacked, and it can laboratories and compare results. Samples must be be picked up with a fork or bucket loader. To handle identical to adequately compare laboratory test re- manure with a solids content of less than 15 to 20% sults. If results are comparable, then select the least as a solid, liquids need to be drained, and the manure expensive laboratory that can return results in the must be dried, or bedding must be added. most timely manner. If results vary, eliminate the At 20% solids or slightly less, liquid may seep from lab or labs that provided the results that varied most. the manure stack, so a tall stack is not feasible. Once From the labs that provided results that are closest solids content exceeds 25%, seepage should not be a together, select the laboratory that can return re- problem, and tall stacks will retain their shape. Poultry sults in the most timely manner. layer manure and poultry litter typically will have 40% solids or more. Bedded swine or bovine manure may Obtaining a Sample have a wide range of solids, but likely will be solid Obtaining a representative sample from each enough to stack easily if adequate bedding is used. manure storage is critical to getting accurate test re- sults. Knowing when to sample, how to collect the Sampling and Testing Manure sample, and how to ship the sample to the testing Many states require producers to have a manure laboratory are all important components of getting nutrient management plan for their operation. Hav- the best representative sample. ing an accurate manure analysis in addition to hav- When to Sample. Manure sampling and testing ing soil analysis and knowing crop yields will help is needed annually to develop a historical track record. increase the accuracy of the plan and the likelihood Research has found that at the same given site with of plan approval by the state. the same given genetics, diet, housing, management, etc., the moisture and nutrient characteristics of the Selecting a Testing Laboratory manure do not change from year-to-year. Preferably, Most laboratories that do soil testing and/or feed a manure analysis should be completed just before analysis also will analyze manure samples. The local the manure will be applied to the land. Extension or NRCS office should be able to assist in In warmer climates of the United States, the time locating laboratories that analyze manure. Contact of year when sampling occurs is critical to obtaining the laboratories before sending samples. To deter- the proper information on lagoon operation. For ex- mine which laboratory best meets your needs, get ample, samples taken during the summer will nor- answers to questions such as the following: mally have lower analysis values than samples taken • For how many years has the laboratory been during the winter. In this case, surface sample dur- performing manure analysis? If possible, ing colder months (e.g. February) then sample the 4 Manure Management Systems Series entire structure in the summer (e.g. July). The other agitation is needed, even during pump out, to ensure option would be to sample annually before manure that the phosphorus and solids stay suspended.