Wednesday, November 15, 2006

Assessment of Nitrogen Supply from Poultry Manure Applied to Corn.

D. A. Ruiz Diaz, J.E. Sawyer, D.W. Barker, and A.P. Mallarino. Iowa State University, 3311 Agronomy Hall, Ames, IA 50011

The common end use of poultry manure is application for crop production. However concerns exist regarding application at rates higher than needed for crop use, with potential for contamination of water bodies due to excess nutrients. Producers also question the proportion of the total N that should be accounted for as crop-available in the year of application. In addition, the economic and agronomic aspects of incorrect application rates also need to be addressed. The purpose of this study is to estimate under field conditions the supply of plant-available N to corn from several poultry manure sources and time of application, and to compare corn yield response between poultry manure N and commercial fertilizer. Manure was applied on producer’s field as strips using two rates. A low rate of approximately 75 lb N/acre and a high rate of 150 lb N/acre based on total N analysis in manure; there was also, a control treatment with no manure applied. Poultry manure N alone significantly increased corn yield in the year of application. Results from the first two years of this study suggest that approximately half of applied poultry manure total N was supplied to corn as available N in the year of application. Corn leaf greenness (CM values) appears to give a better reflection of poultry manure N supply to corn than late spring soil nitrate concentrations. Continued work with more poultry manure sources and field applications will help clarify estimates of first-year N supply.