Northern Research and Demonstration Farm
An experiment was conducted from 2000–2003 to document yield responses to chicken manure applications made during the winter and spring at two different rates. The focus was on response to nitrogen from manure rather than from phosphorus or potassium.
Iowa State University
Holmes, John D. and Rueber, David, "Yield Responses to Winter Application of Chicken Manure" (2004). Iowa State Research Farm Progress Reports. 1396.