Southeast Research and Demonstration Farm
Swine manure is readily available in Iowa and is an excellent source of fertilizer for crops. Application rates are often based on the nitrogen (N) needs of the coming year’s crop. Producers often ask how much N is available the first year, and if any N carries over to subsequent years.
Iowa State University
Brenneman, Greg and Van Dee, Kevin, "Swine Manure Nitrogen Availability and Carryover" (2005). Iowa State Research Farm Progress Reports. 1298.