Ohio Livestock Manure Management Guide

Bulletin 604-06

Appendix B - Reporting Manure Analysis Results

Guidelines for Reporting Manure Analysis Results

Manure analysis reports should provide information that is easy to use and interpret and should help fulfill the record-keeping needs of the customer. Ideally, livestock producers should be able to look at analysis reports from several different laboratories and be able to come to similar conclusions regarding application rates and nutrient credits for their manure. This may not be realistic, due to different approaches to estimating nutrient availability. The guidelines presented here are suggested in order to encourage dialogue within the testing industry that will result in some level of standardization of reporting, with simplicity and ease of interpretation being the primary goals. Two example laboratory reports are given to illustrate the guidelines suggested. Any number of formats can work equally as well, as long as the information presented and the purpose for presenting it is clear to the customer.

Descriptive Information

Descriptive information should include the following:

• Laboratory name, mailing address, telephone number, e-mail address.
• Customer name, mailing address, telephone number, e-mail address (farmer name also, if different than customer).
• Sample identification (laboratory number and customer-provided identification).
• Sample description (at a minimum, include livestock species, liquid or solid, manure application method; may also include storage and handling system, application timing, days until incorporation).
• Date of analysis and date of reporting.

Sample submission sheets should have spaces for customers to record the needed information. The more information the customer can supply about the sample, the more assistance the laboratory can provide for interpreting the results. Having this information on the analysis report also simplifies record keeping for the customer.

Analysis Results

Units and Reporting Basis

Report dry matter as percent solids, to at least the nearest 0.1%. Samples should always be analyzed for total solids content, and the results reported (rather than moisture content), even if the customer does not request it specifically. Dry matter determination is often necessary to convert the results of analyses performed on dried samples to an as-is basis. Also, most laboratories include solids in the fee charged for routine manure analysis. Reporting of dry matter or solids content also makes it easier to compare results between different samples.

Report total nitrogen (N), ammonium-nitrogen (NH₄+-N), calculated organic N, total phosphorus as phosphate (P₂O₅), total potassium as potash (K₂O), and other minerals in units of lbs/1,000 gal for manures applied as liquids, and lbs/T for manures applied as solids. A strong effort should be made to obtain the desired reporting units from the client. The type of spreader being used will dictate how the results should be reported, not the dry-matter content. If a particular dry-matter level is used to generate reporting units, there should be an option in the computer program to over-ride this default if the sample dry matter falls outside the normal dry-matter ranges for liquid and solid manures.

Report N, NH₄+-N, P₂O₅, and K₂O to at least the nearest 0.1 lb/1,000 gal or lb/T to provide consistency for samples with low concentrations of particular nutrients. Do not report beyond the number of significant digits that are appropriate for the analysis methods and calculations you are using. Report phosphorus and potassium as P₂O₅and K₂O. This is necessary to be consistent with standardized reporting of soil fertility recommendations and nutrient content of fertilizers.

Results may also be reported in units of percent or ppm, but these should be reported separately from the results reported as lbs/T or lbs/1,000 gal and should be clearly labeled in order to prevent confusion. It should then be indicated on the report which values should be used to calculate application rates and nutrient credits.

Results reported in units of percent or ppm should be reported on an as-is basis. Results reported on a dry-matter basis can be useful for comparing results between different manures, or for generating more accurate table values for different regions. Most producers, however, will have little use for dry-matter basis results. If they are reported, they should be clearly labeled, and the relationship between different units should be indicated. Dry-matter content should always be reported, to allow conversion of results to dry-matter basis results, if desired.

Conversion Factors

Most conversion factors are simply mathematical standards used by all laboratories. These include multiplying percentage by 20 to get lbs/T, multiplying ppm by 10-4 to get percent, multiplying P by 2.29 to get P₂O₅, multiplying K by 1.2 to get K₂O, and multiplying dry-matter basis results by the dry-matter fraction to get as-is basis results.

For liquid manures, the factor used to convert percentage to lbs/1,000 gal is based on the density of the sample, and different laboratories use different factors. Some laboratories use the density of water (8.33 lbs/gal) and others use measured or estimated density values. This is done to account for the presence of solids in liquid manures and thereby improve the accuracy of the reported value. This practice is probably not justified, however.

In order to assess the affects of solids content and manure density on conversion factors and reported analysis values, 262 liquid dairy and swine manures from a variety of storage and handling systems were analyzed for density, solids content, specific gravity and total nitrogen (N) content (Jarman, 1999). The samples ranged in solids content from 0.3 to 16%. Nitrogen content in lbs/1,000 gal was calculated using the density of water, measured sample density, or measured specific gravity, or an estimated density of 9 lbs/gal.

Calculated N content in lbs/1,000 gal was similar when based on specific gravity, measured density or the density of water. Significantly larger N content values were obtained when a density value of 9.0 lbs/gal was used. Therefore, in order to standardize results between laboratories, it is recommended that the density of water (8.33 lbs/gal) be used, and percentage (as-is basis) would then be multiplied by 83.3 to obtain lbs/1,000 gal.

If standardized conversion factors are used, it is not necessary to report these factors. If they are reported, caution should be used in their placement on the report. In order to streamline the report and avoid confusion, conversion factors and calculations could be placed on the back of pre-printed reporting forms.

Accuracy of Reported Results

All results should be examined for transcription and other errors. The results should fall within the expected range of values for that manure type, unless unusual conditions are present. Computerized calculations should be checked for accuracy, and assumptions used in computer generation of numbers should be updated periodically. Every number on every report should be checked and verified before it leaves the laboratory.

Interpretive Information

Nutrient Availability Estimates

Differences in factors that affect manure nutrient availability do exist between regions and states and even within states. The use of consistent values across large regions would be inappropriate.

The simplest solution for dealing with differences in nutrient availability is to report only the actual analysis values and refer customers to their State Extension Service for assistance in determining nutrient availability, application rates, and nutrient credits. However, many laboratories want to provide these services to their customers. Information about nutrient availability and how to calculate nutrient credits and application rates does help producers interpret their results, as long as the information is correct for that producer. Providing availability factors (percentage of total nutrients available) rather than calculating the amounts of nutrients available, solves the problem of incorrect calculations in situations where insufficient information is provided by the customer to accurately determine the correct availability factors to use. However, providing amounts of available nutrients instead of availability factors can make it easier for the producer to interpret the results.

Regardless of the availability values provided, the actual analysis results should always be reported first, and the source of the availability values should always be stated prominently on the report, especially for the benefit of out-of-state customers. Availability values should not be considered as transferable between states. Laboratories should also check each report to ensure that the values provided (and the factors on which they are based) apply to that customer’s particular sample. Due to development of new storage, handling, and application methods and the availability of their own large databases of manure nutrient content, laboratories could also help gather information to assist Extension in developing or modifying availability factors for their region.

Manure Nutrient Value

The economic value of manure nutrients is only equal to the cost of the fertilizer that is being saved on the particular fields to which the manure is applied and must account for application costs. Unless a laboratory has access to information about fertility levels, crops being grown, manure and fertilizer rates applied, and application costs for each of a customer’s fields, then estimates of manure nutrient value are usually inaccurate and misleading. These estimates may provide some value to a producer as long as he or she understands what is being estimated.

References

Jarman, J. K. 1999. Fact sheet on use of liquid manure density values in reporting manure nutrient analysis results. Laboratory Certification Programs, Minnesota Department of Agriculture, St. Paul, Minn.

Peters, J., S. Combs, B. Hoskins, J. Jarman, J. Kovar, M. Watson, A. Wolf, N. Wolf. 2003. Recommended methods of manure analysis. [Online]. Available at uwlab.soils.wisc.edu/pubs/A3769.pdf (Posted March 4, 2003; verified March 6, 2003).

Example Laboratory Report 1 (analysis results only, no interpretive information)

Laboratory Name

Laboratory Address

Tel. No. Fax No.

E-mail Address

Example Laboratory Report 2 (analysis results plus interpretive information)

Laboratory Name

Laboratory Address

Tel. No. Fax No.

E-mail Address