Nitrogen from animal manures

Domestic animals in the USA produce over 1, 032, 000, 000 Mg of manure each year, resulting in 7, 570, 000 Mg of excreted nitrogen (N). If manure is to be used in a way to maximize its agronomic benefits as a nutrient source and at the same time minimize the potential environmental impact of the nutrients, an accurate estimate of the nutrient content must be determined. Historically, manure applications to cropland have been made based on the ability of the manure to supply N. They have major economic effects for the livestock and crop producer. Undisturbed cores provide a more reliable assessment of N availability, but the number of cores needed makes it impractical for field-scale predictions. A producer’s decisions regarding manure application management are the ultimate integrator of all the science and nonscience factors involved with manure N.