FOR IMMEDIATE RELEASE
Contact:Laura L. Jackson, UNI associate professor of biology, (319) 273-2705 or email <laural.jackson@uni.edu>
Vicki Grimes, Office of Public Relations, (319) 273-2761
CEDAR FALLS, Iowa — As the trend in hog production in Iowa continues to shift from smaller dispersed farms to fewer, more concentrated operations, a University of Northern Iowa biology professor and two colleagues investigated whether or not Iowa's manure management regulations for livestock are sufficient to protect water quality. The short answer is no.
“People worry about lagoon spills and accidents,” said Laura Jackson, UNI associate professor of biology, “but we were more interested in normal, everyday practices.”
Jackson, Dennis Keeney, former director of the Leopold Center for Sustainable Agriculture, and Elizabeth Gilbert, a longtime resident of the Iowa Falls area, looked at public records on the manure management practices of 10 confined animal feeding operations (CAFOs) in a 6-square-mile area in north central Iowa.
The results of the study, funded by the Iowa General Assembly through Iowa State University, and the U.S. Department of Agriculture's Fund for Rural America, have been published in the latest issue of the Journal of Soil and Water Conservation.
All 10 of the CAFOs were located in Hamilton County, which has a high density of swine facilities. Half of the operations used lagoons for manure storage and half used earthen basins.
According to state regulations, CAFOs with space for more than 1,333 market-weight hogs (up to 250 lbs.) must submit a manure management plan to secure a construction permit. The researchers used these plans, which are public records, to study the balance between hogs and land. They compared the plans to the most recent recommendations of Iowa State University agricultural engineers.
They found that too much manure from the CAFOs was being applied to too little land. Three times as much land would be needed for the nitrogen in the manure, and 10 times as much land would be needed for the phosphorus content, according to Jackson.
“Our study offers conservative estimates of what hog producers are actually doing,” said Jackson. “When readers look at our numbers, they have to remember that hog producers have a strong economic incentive to dispose of manure inexpensively.”
The CAFOs legally minimized the land area needed to apply manure in three ways. First, they underestimated the amount of nitrogen in the available manure. Over 70 percent of the nitrogen is estimated to escape into the atmosphere as ammonia, but then the ammonia returns as rainfall.
Second, they projected above-average crop yields, and finally they applied manure to the same field year after year, whether the crop was corn or soybeans. (Soybeans, which fix nitrogen naturally, are not usually given additional nitrogen fertilizer.)
In one case, a field was counted twice, the researchers noted, and the size of some fields was overestimated.
Jackson estimates that one square mile of corn/bean cropland in Hamilton County could absorb the phosphorus generated by about 1,660 hogs. According to their manure management plans, the 10 CAFOs in the study area averaged about 10,000 hogs per square mile.
The researchers conclude that even if loopholes were closed, Iowa's laws would still fail to protect its waters from pollution derived from hog manure. They recommend:
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