STEP 1   Manure Sampling

Manure samples can vary greatly in their nutrient content, due to factors such as the type and age of the animal, the nutrient content of the feed, bedding material, feedwater, wastewater, storage and handling. The nutrients in manure are not distributed evenly between the urine and feces. Average nutrient values are available for various manure types, but sampling of manure based on different pens, animal age and bedding content is important to understand the nutrient content of the resource. Nutrient levels in 25 samples taken from one feedlot pen ranged over an order of magnitude (Gillund et. al. 1999). Therefore, obtaining a representative sample is critical to a good analysis.   When sampling manure for nutrient content, submit the sample for analysis as close to the time of field application as possible. The best time for collecting a sample is during loading and/or land application.

Why Sample Manure?
1. To determine the nutrient content.
2. To determine the rate of application.
3. To determine additional nutrients required for crop production.
4. Manure is variable in nutrient content and sampling helps to identify the differences.

Sampling Liquid Manure:

1. Samples should be taken each time the storage is emptied, because nutrient status varies with the time of year.

2. Agitate the storage completely before taking samples.

3. Nutrient status varies with the depth of storage, so collect the sample in a container from various depths as it is being emptied. Thoroughly mix 10 to 20 of the samples from each depth and transfer a portion to a plastic jar. The jar should only be half full to avoid gas buildup and potential explosion.

4. Seal the sample tightly and store it in a cool place. It should be submitted to the testing lab within 24 hours.

Sampling Solid Manure:

1. Sample manure each time the storage is emptied, until a trend is evident in the results. Then samples can be done every few years or when a change in management occurs (bedding, storage etc.)

2. Remove the crust to sample into the pile.

3. Take a sample (using a pitchfork for example) from various parts of the pile. Try to take into account visible variations in bedding and moisture content.

4. Place the sample on a clean cement pad or plywood. Chop the manure with a shovel or fork and mix the samples as thoroughly as possible.

5. Divide the manure into four portions and discard three.

6. Continue dividing and mixing sample until you can fill a half-litre shipping container. Store the sample in a tightly fitting container in a cool place, and submit to the testing lab within 24 hours.

Analyzing Manure

A number of qualified laboratories exist for manure analysis. Manure samples should be analyzed for moisture content (solid manure), total nitrogen (N), ammonium (NH4-N), total phosphorus (P), and total potassium (K). Nitrate N also can be analyzed but is usually very low in manure. Additional manure analyses could also include: E.C., SAR, C/N ratio, pH, and sodium. Individual operators can develop a manure nutrient-content database by analyzing manure samples over a number of years. Generalized values are based on an average from a variety of sources, but actual farm values may vary greatly.

The total amount of nutrients in manure is not as important as the availability of these nutrients. Nitrogen and phosphorus can be in the organic portions of the manure and are not available until they are transformed (mineralized) into inorganic nutrients. The two main forms of N in manure are organic N, which is unavailable, and ammonium N, which is the predominate component of available N. Nitrate N is a small fraction of the inorganic N in manure. The process of nitrification will eventually convert all the ammonium N to nitrate N, which is available for plants to use.