Manure Testing
Manure Testing
Definition
Livestock manure testing is the process of evaluating manure nutrient content in a laboratory to provide specific agronomic and environmental recommendations for manure use.
Purpose
Managing manure for economically optimum crop production with minimum environmental impact requires knowledge of manure nutrient content. While “book” values listing average nutrient contents of manures are available, they are of limited value since manure properties vary widely with animal feeding programs and manure management systems. Testing representative manure samples is needed for the accurate determination and appropriate management of manure nutrients.
How Often to Sample?
Manure sampling and testing should occur annually for four to five years to develop a historical track record. If the site has covered manure storage and the same animal genetics, diet, housing, and manure management practices are utilized, then manure characteristics should not change drastically from year to year. Testing could be reduced to every three for four years in these covered systems after adequate data has been accumulated. If manure is stored uncovered and is influenced by the weather, or if management practices change (i.e., manure management system upgrades or dietary changes), then sampling and testing annually is recommended. Additionally, for regulated facilities, manure testing more frequently may be required. Therefore, it is important to know your state’s regulatory requirements for manure testing prior to application.
Obtaining a Representative Manure Sample
Samples submitted for testing should be representative of manure as it is used/spread. Multiple samples are generally necessary to better represent variability in manure characteristics. Composite sampling is the recommended method of addressing variability in manure properties without the added cost of submitting multiple samples for analysis. Composite sampling involves collecting multiple samples from a single source, thoroughly mixing this material, and submitting a sub-sample for analysis.
Representative sampling must take into consideration the form of manure as well as the particulars of storage and handling. For solid manures, it is generally recommended that samples be obtained from loaded spreaders. Due to segregation of liquid and solid fractions during storage in earthen basins, pits, or tanks, slurries and liquids should be thoroughly agitated for a minimum of 2-4 hours. If only the surface liquid of the lagoon will be land applied, there is no need to agitate prior to sampling.
Solid manure sampling
Sampling while loading (stack and bedded pack)
- Collect at least five samples from several spreader loads.
- Mix and collect a 1-pound subsample.
Sampling during spreading
- Drive spreader over tarp and collect several samples from tarp.
- Mix and collect a 1-pound subsample.
Sampling daily haul
- Place a bucket under barn cleaner while loading spreader. Repeat sampling 4-5 times.
- Mix and collect a 1-pound subsample.
Sampling broiler houses
- Collect 8-10 litter samples collected at random from across the house to the depth that will be removed during cleanout.
- Areas near feeders and waterers should be sampled in proportion to their spatial distribution in the house.
- Mix and collect a 1-pound subsample.
Sampling stockpiled manure
- Collect 10 samples from various locations within the pile at least 18 inches below the surface.
- Mix and collect a 1-pound subsample.
Sampling slurries and liquid manures
Sampling from storage tanks or pits
- Agitate manure thoroughly (2-4 hours minimum) and obtain at least five samples while loading. Combine them in a five-gallon pail.
- Mix and collect a 1-quart subsample.
Sampling from liquid lagoons
- Use a container attached to a pole to collect at least 10 sub-samples from around the lagoon.
- Collect sub-samples at least 6 feet from the lagoon edge and from a depth of around 1 foot.
- Avoid collecting at the very surface and avoid debris and scum.
- Mix subsamples and collect a 1-quart sub-sample.
Sampling during application
- Place five pails around field to catch manure from spreader or irrigation equipment.
- Mix and collect a 1-quart subsample.
Subsamples should be placed in plastic containers (liquids or slurries) or sealable plastic bags (solids), and then double-bagged to prevent spills. Never use glass containers, as pressure buildup can cause the container to break creating a hazard for laboratory staff and risking loss of the sample. Cool or freeze the samples immediately and send to a laboratory that is proficient in manure nutrient testing as soon as possible.
Manure Phosphorus Tests
Agronomic Tests
A variety of methods have been developed to evaluate the phosphorus content of manures for agronomic interpretation. These tests generally determine total phosphorus concentrations in manure through chemical digestion, though some laboratories still use an ashing technique.
Manure testing reports should present this concentration as phosphate (pounds P2O5 per ton, or pounds P2O5 per 1000 gallons). However, in some instances, results may be presented as elemental phosphorus (pounds P per ton or pounds P per 1000 gallons). It is important to note how results are reported so that appropriate land application rates can be calculated.
Environmental Tests
A number of states have developed phosphorus indices for field management that employ water-extractable phosphorus in manure as an indicator of the relative availability of manure phosphorus to loss pathways, such as overland flow and leaching. Water-extractable phosphorus in manure varies between livestock species, with different storage/handling methods, and as a result of the addition of “phosphorus-sorbing materials,” such as alum (aluminum-sulfate).
References
Brimmer, R., Floren, J., Gunderson, L., Hicks, K., Hoerner, T., Lessl, J., Meinen, R. J., Miller, R. O., Mowrer, J., Porter, J., Spargo, J. T., Thayer, B., Vocasek, F., & Wilson, M. L. (2022). Recommended Methods of Manure Analysis (M. L. Wilson & S. Cortus, Eds.; 2nd ed.). University of Minnesota Libraries Publishing. https://doi.org/10.24926/9781946135858
For Further Information
Contact your local agricultural analytical laboratory, conservation district, USDA-NRCS or Cooperative Extension office. To find your local USDA Service Center, visit https://www.nrcs.usda.gov/contact/find-a-service-center. For a current list of laboratories that participate in the national Manure Analysis Proficiency (MAP) program, contact the Minnesota Department of Agriculture.
Current Authors
| Melissa Wilson University of Minnesota mlw@umn.edu Peter Kleinman |
Stephanie Kulesza North Carolina State University sbkulesz@ncsu.edu |
Previous Authors
| Anne Wolf Penn State University |
John Peters University of Wisconsin |
Editing and Design
| Deanna Osmond NC State University |
Forbes Walker University of Tennessee |
Citation:
Wilson, M., S. Kulesza, and P. Kleinman. 2023. Manure Testing. SERA17 Phosphorus Conservation Practices Fact Sheets. https://sera17.wordpress.ncsu.edu/manure-testing/