One of the most critical and often most difficult parts of manure testing is collecting a representative sample for analysis. The most important thing to remember in sampling manure is that the sample must represent the actual manure being spread. If sampling is not done correctly, the results of the analysis can be worse than not having an analysis at all--your nutrient management plan will not be accurate.
General Manure Sampling Guidelines
- Sample at or near the time of field application.
- Take multiple sub-samples and mix these thoroughly and then take a composite subsample of this mixed manure for analysis.
- Collect a single composite sample from uniform sources of manure achieved by agitation or mixing. Collect several separate composite samples from areas where manure is obviously different.
- Long term average manure analysis, if management is consistent, is often better than any one individual analysis.
- Sample on a regular basis and keep records of analysis to evaluate trends and react to changes.
Sampling procedures vary depending on whether the manure is a solid or a liquid. Also, for each manure type there are several possible ways to collect a representative sample. Sampling Livestock Waste for Analysis in the publication “Recommended Methods of Manure Analysis” provides concise and practical guidelines for sampling different types of manure. The suggested sample procedures below are taken from that reference.
Solid Manure (left) and Liquid Manure (right) Require Different Sampling Techniques.
Tips for Making Sure Your Manure Sample Reaches the Lab In Good Condition
- Carefully follow all instructions from your manure testing lab for handling and delivering the samples to the lab. Most labs recommend freezing samples until they can be delivered to the lab.
- Try to send samples early in the week and avoid sending samples so that they arrive at the lab on weekends and holidays so that the samples do not sit around for any longer than necessary.
- Improper handling can result in inaccurate results. Be sure to completely fill out the lab information sheet that goes with the sample.
Related Web Pages
Page Authors: Douglas Beegle, Pennsylvania State University and John Peters, University of Wisconsin