The short answer to this question is “definitely not.” Nutrient content in manure is affected by pre- and post-excretion factors. Animal species and category as well as nutritional status (feeding level, feed types, and nutrient profiles) will influence quantity and quality of nutrients excreted in manure. A number of management and environmental factors can also influence manure composition after excretion (post-excretion). Manure handling practices, manure temperature, and wind speed are some of the factors that can affect nitrogen and sulfur volatilization. Length of storage and storage type will both affect amount and form of volatilized compounds. During the heat of summer, most urinary nitrogen can be lost from the dairy barn floor before reaching the manure storage. On the other hand, it has been shown that as much as 40% of the nitrogen lost from a swine operation may be lost from the manure storage facility as dinitrogen (N2), a harmless gas.
Tables containing typical figures and equations to estimate manure nutrient contents are available for most economically important species from numerous sources such as the National Feed Management for Livestock and Poultry, the MidWest Plan Service, and the American Society of Agricultural and Biological Engineers. Nonetheless, given the number of aspects influencing composition, it is advisable that a tightly sealed sample of manure (composited from a number of subsamples collected at different depths and sites) be quickly sent for nutrient analysis in a qualified laboratory.
Vinicius R. Moreira, Louisiana State University AgCenter Southeast Research Station
