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.
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.)
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.