Ames, Iowa-Poultry manure is an effective – and, if applied properly, environmentally friendly – fertilizer, according to studies going on since 1998 at Iowa State University. Evaluating both impact on crop production and surface and groundwater quality, ISU researchers compared nitrogen treatments during the spring of 150 and 300 pounds per acre poultry manure and 150 pounds per acre UAN on nine one-acre field plots. Control plots where no nitrogen was applied were included. Poultry manure applied at the 150 pound per acre rate resulted in lower nitrate and phosphate concentrations in subsurface drainage water, compared with equivalent application rates of commercial nitrogen, reported Ramesh Kanwar, chair of the ISU agricultural and biosystems engineering department and lead researcher on this project. “Nine years of data shows corn yields are the highest on the plots receiving 300 pounds of nitrogen from poultry manure,” Kanwar said. “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.
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