Yesterday the State Environmental Protection Commission opted not to ban the practice of spreading manure on soybeans. It was another sign that Governor Terry Branstad’s mission to reorient that commission toward agricultural interests has succeeded.
Most famers do not apply nitrogen-based fertilizers to soybean fields, because the plant takes nitrogen from the air. The corn/bean rotation became standard practice in Iowa precisely because soybeans fix nitrogen in the soil. In contrast, growing corn year after year would rapidly deplete the soil.
The Sierra Club’s Iowa chapter provided background on the issue in this action alert (emphasis in original):
In consideration of the potential for nitrogen from manure applied to soybeans to contaminate water resources, the Environmental Protection Commission (EPC) in November 2006 initiated rulemaking to limit liquid manure applications to soybeans to 100 pounds of nitrogen per acre and to impose a total ban on applying liquid manure to soybeans five years later, unless further scientific research supports alternative action.
As part of the rulemaking, the EPC stipulated that it must review available scientific evidence and affirm or rescind the ban of applying manure to soybeans. The EPC will vote to affirm or rescind the ban at its October 16, 2012, meeting.
Soybeans are a legume crop and they can biologically absorb the nitrogen they need from the atmosphere. Therefore, nitrogen fertilizer is traditionally not applied to soybeans. However, with the increasing numbers of Concentrated Animal Feeding Operations (CAFOs) in Iowa, liquid CAFO manure – containing high levels of nitrogen – is now sometimes applied to soybeans.
Published scientific research – as well as common sense – indicates that applying manure to soybeans increases the potential for nitrogen to leach into tile drains and contaminate our water resources.
Five years later, two peer-reviewed studies and one unpublished report indicate that applying liquid manure to soybeans significantly increases the amount of nitrates in our water. The three studies appear to be the only studies that have measured nitrate leaching when manure was applied to soybeans. All of these studies found increased leaching of nitrogen to groundwater, and all were published since the 2006 EPC rulemaking, which stipulated that in five years “the commission shall review the available scientific evidence and determine whether any further or alternative action is necessary.”
Given that recent studies have documented increased nitrogen leaching to water resources when manure is applied to soybeans and that the agronomic advantages of applying manure to soybeans are negligible, the Sierra Club strongly urges the Environmental Protection Commission to affirm the ban on applying manure to soybeans. The convenience of disposing of manure on soybean ground is not worth the water quality degradation it can cause.
See more information about the rule and the studies as they were presented to the Environmental Protection Commission in September 2012, and read an analysis of the studies by Francis Thicke, Ph.D.
Tell the EPC to ban liquid swine manure on soybean fields.
The published research articles are here (pdf). Thicke’s two-page analysis is less technical and more accessible to people outside the field of agronomy. Iowa Citizens for Community Improvement boiled down the case against manure on soybeans to a few paragraphs.
Members of the state Environmental Protection Commission were persuaded by the major agricultural groups that testified against banning manure application on soybeans. I can’t say I’m surprised. The commissioners tend to defer to CAFO interests, and one of them builds factory farm facilities for a living.
It’s unfortunate that the headline for the Des Moines Register’s blog post on the commission meeting was “Environmental panel calls cops on CCI, adjourns meeting without acting.” I appreciate the work Iowa CCI does to call attention to water pollution problems, but something is wrong when your disruptive protests become the news lead for a good environmental reporter like Perry Beeman. The story should be about how runoff from soybean fields affects groundwater and why soybeans don’t need hog manure to grow. Shouting down members of a state commission drew the media focus away from that issue, as happened when Iowa CCI members heckled Paul Ryan at the Iowa State Fair.
UPDATE: Thicke commented on Facebook,
The first [Iowa State University] presentation by Dr. Matt Helmers clearly showed how applying manure to soybeans — even at the lower rate of 100 lb of N/acre — significantly increased nitrate leaching to groundwater. The second ISU presentation by Dr. John Sawyer muddied the waters by using irrelevant data, extrapolation and speculation to conclude that theoretically 100 lb of manure N/acre shouldn’t cause nitrogen leaching — even though Dr. Helmers had just showed real, multiyear, replicated data to the contrary. The second presentation no doubt confused the EPC [Environmental Protection Commission] and the reporter, leading them to believe the flawed theory over the actual data. ISU couldn’t have orchestrated that better if it had intentionally intended to carry water for the pork industry.
Speaking of CAFOs and Iowa water quality, the U.S. Environmental Protection Agency has extended the public comment period on regulation of CAFO pollution until October 31. Click through for the contact information of the relevant EPA staff. This comment period relates to the EPA’s preliminary report criticizing the Iowa Department of Natural Resources for not enforcing the federal Clean Water Act on CAFOs. The DNR responded to the EPA’s findings a few weeks ago.