Date of this Version
NebGuide G1780, University of Nebraska-Lincoln Extension, Institute of Agriculture and Natural Resources, November 2007.
Manure testing is necessary to make optimum use of manure while protecting water resources. This publication is a guide to providing information on a Manure Sample Submission Form for reliable interpretation of results.
The tests most frequently needed to optimize nutrient management are total and ammonium nitrogen (NH4-N), phosphorus (P2O5), potassium (K2O), pH, soluble salts, sodium, and dry matter content.
Nitrogen. Manure contains both organic and inorganic forms of nitrogen. Ammonium-N is the primary inorganic form in manure and is readily available to crops. Nitrate-N concentration is usually too small to affect management decisions, unless the manure is composted.
Organic nitrogen is the difference between total nitrogen and inorganic nitrogen. Organic nitrogen becomes available to plants as manure decomposes, with 20 percent to 50 percent of organic nitrogen available to the first crop after application. Much of the remaining organic nitrogen becomes available in subsequent years.