Aromatic Gold: How to Take a Sample to Determine the Value of Manure

One of the least sought-after tasks on the farm, manure sampling, is also one of the most profitable!

Manure supplies nutrients for crop growth, organic matter for soil conditioning, and decreases the need to purchase off-farm nutrients. Manure analysis will give a tangible depiction of the amount of nutrients available.

The nutrient content of each type of manure will vary, depending on livestock genetics, feed ingredients, type of bedding, and the amount of washwater or other liquids. These factors affect the amount of N, P and K in the manure.

Samples, especially of liquid manure being applied to a corn crop, can be separated by storage or by field. The nutrient concentration can vary from top to bottom, depending upon the uniformity of agitation. Phosphorus is generally higher in the solids portion of manure, while potassium is generally higher in the liquid portion. Ammonium-nitrogen is highest in the liquid portion.

A manure storage should be sampled each time the storage is emptied for several years, until the results are consistent. This will also help create a database of the nutrient content generated in your farm operation.

Analysis should include total nitrogen, ammonium-nitrogen, phosphorus, potassium and dry matter content. Copper and zinc analysis are also useful for operations supplementing these micronutrients in the ration.

Solid manure is more difficult to sample because there is no agitation process, resulting in variations within solid storages. For this reason it is recommended that samples be separated by field rather than storage.

How to Sample Liquid Manure

Agitate manure storage thoroughly.

Collect random sub-samples of manure from various depths in the storage.

The sampling should take place while the storage is being emptied (i.e., every 10 loads or every 30-60 minutes from a drag hose pump.

Use a clean plastic pail to collect samples.

Mix 10-20 sub-samples thoroughly in a larger pail and transfer a small sample to a plastic jar (supplied by laboratory). Fill jar only half full to allow room for gas buildup. Store in a cool place until sending the sample to the lab.

Consider taking another sample when applying to a different field to document the analysis for each field.

When results from the manure analysis are received, keep records and adjust any additional nutrient applications to the field.

How to Sample Solid Manure

1. Samples of solid manure can be taken from the spreaders during application or from the top, middle and bottom of the storage.
2. On clean concrete or a plywood surface, take sub-samples (a forkful) of manure from several different loads throughout the application or from the different areas of storage.
3. Chop and mix the sub-samples together using a fork or shovel.
4. Divide the larger sample into four equal parts and discard three.
5. Continue to mix and subdivide until you have a sample that will fit into a plastic bag or sample jar.
6. Place sample jar into a plastic bag and ship to lab as per liquid sample.
7. Repeat sampling procedure if a portion of the manure will be applied to a different field or if the dry matter content is significantly different (dry vs "soupy").
8. Each storage system (or areas within the same storage with different dry matter contents) should have its own sample taken to reflect dry matter and specific nutrient content.

Manure samples should be stored in a cool place until they are shipped to a laboratory. Shipping a sample so that it arrives at the laboratory on a week day is recommended to ensure immediate processing. Sending samples through the post office is not recommended.

By Christine Brown,Nutrient Management Lead/OMAFRA
Pork News & Views newsletter (December 2008)
Government of Ontario Ministry of Agriculture, Food and Rural Affairs