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Iowa State Studies Long-Term Use of Poultry Manure
January 25th, 2007
AMES, Iowa -- Nine years of research data at Iowa State University shows poultry manure is an effective fertilizer that, when applied properly, also is environmentally friendly.
The study began in 1998 to evaluate the impact of poultry manure applications on crop production 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. Control plots where no nitrogen is applied also are a part of the project.
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 and phosphates, and yields are determined.
The key finding is that poultry manure applied at the 150 pound per acre rate resulted in lower nitrate and phosphate concentrations in subsurface drainage water when compared with equivalent application rates of commercial nitrogen fertilizer.
"Nine years of data shows corn yields are the highest on the plots receiving 300 pounds of nitrogen from poultry manure," said Ramesh Kanwar, chair of the ISU agricultural and biosystems engineering department and lead researcher on this project. "Yet the 150 pound nitrogen rate of poultry manure produces the second highest yields, and compares favorably to yields on plots that received commercial fertilizer."
Kanwar said the research also shows that when poultry manure is applied at a higher rate than needed to meet a corn crop's nitrogen needs, such as the application of poultry manure at the 300 pound rate, the impact on water quality is greater.
"This study shows that using poultry manure at lower rates reduces the nutrient losses to groundwater and gives some of the best crop yields under a corn-soybean system," Kanwar said.
This research project, funded by the Iowa Egg Council, will continue for two more years.