ISU Reseachers Find Poultry Manure Boosts Yields, Protects Water

September 27th, 2004

Research at Iowa State University shows the manure generated by an increasing number of Iowa poultry operations is an effective, environmentally friendly fertilizer.

A six-year study was initiated to determine the impact of poultry manure applications on nutrient uptake by crops, and on surface and groundwater quality. Three nitrogen treatments are being investigated - both 150 and 300 pounds per acre of nitrogen from poultry manure, and 150 pounds per acre from a commercial fertilizer of urea-ammonium nitrate.

The research involves nine, one-acre field plots at an ISU research farm west of Ames. All nitrogen applications are made in the spring. Both subsurface and surface water samples are collected and tested for nitrates, phosphates and bacteria.

After five years of data collection, researchers say they have some important answers. "The key finding is that poultry manure applied at the 150 pound per acre rate resulted in lower nitrate, phosphate and bacteria concentrations in subsurface drainage water when compared with equivalent application rates of commercial nitrogen fertilizer," said Ramesh Kanwar, chair of the ISU agricultural and biosystems engineering department and lead researcher on this project. "In addition, we've found relatively higher crop yields with poultry manure when compared with the commercial fertilizer at the same rates."

Kanwar said the research also shows that when poultry manure is applied at a much higher rate than is needed to meet the nitrogen-uptake needs of a crop, such as the application of poultry manure at the 300 pound rate, the impact on water quality is greater and crop yields don't increase significantly. "This demonstrates that responsible application of poultry manure is just as important as it is with commercial fertilizer," Kanwar said.

This project, funded by the Iowa Egg Council and the Leopold Center for Sustainable Agriculture, will continue for one more year.


Ramesh Kanwar, Agricultural and Biosystems Engineering, (515) 294-1434,
Susan Thompson, Communications Service, (515) 294-0705,