SOIL FERTILITY
Scientists developing strategies for upcoming phosphorus mandates

Jim Barlow, Life Sciences Editor
(217) 333-5802; b-james3@uiuc.edu

12/1/2001

CHAMPAIGN, Ill. — A reality of Illinois agriculture is phosphorus, a consequence of keeping soils fertile to produce food, feed and fiber. University of Illinois researchers say that around the state, levels of soil-test phosphorus range from a low five pounds per acre to an excessively high 1,000 pounds per acre. High levels often are associated with long-term manure or sewage sludge applications.

A day of reckoning is coming in the form of a decision by the U.S. Environmental Protection Agency to apply standards on either soluble or total phosphorus, said Robert Hoeft, a professor of soil fertility in the UI department of crop sciences. Hoeft has been leading a state-mandated research effort to understand what is happening with phosphorus and what to do about it.

Unchecked, phosphorus and its fertilizer-based-cousin nitrogen become part of the eutrophication process that leads to the oxygen-choking growth of excess algae – a problem the EPA says affects as much as half of U.S. waters. Agriculture and community sanitation systems rank as the biggest suppliers of phosphorus in Illinois.

"We have identified the factors that affect the runoff of phosphorus into the environment, and we've identified them in a way so that we can manage them to minimize that runoff into our lakes and streams," Hoeft said. "We are confident that when the EPA decides which form of phosphorus it wants us to set standards on, we will have management strategies that will help farmers, if they follow our recommendations, reduce the chances their phosphorus runs off their land."

UI researchers have been working on the issue since the Illinois Livestock Management Act took effect in January 1998. Hoeft detailed the UI effort in October at the annual meeting of the American Society of Agronomy in Charlotte, N.C. He is about to embark on a series of meetings around the state to share their data and potential remedial recommendations with fertilizer and seed dealers.

The UI expects the EPA to opt for standards on total phosphorus, Hoeft said. If so, farmers will be urged to convert more of their cropland into a no-till soil-conservation strategy to reduce erosion and runoff. The UI also would suggest the injection of liquid manure and fertilizer into the soil just below the surface. Scientists are achieving good results using a lift-and-drop method that helps maintain the protective residue of groundcover on no-till fields.

If the EPA instead targets soluble phosphorus, farmers would be advised to maintain soil phosphorus for optimum crop production, inject all phosphorus materials and reduce erosion.

"We should not be getting high phosphorus field tests," Hoeft said. "Continually applying manure is going to continue to build phosphorus levels up. We need to be putting the manure below the surface and, in many cases, moving excess manure further on down the road to get it to fields in need. Based on the data that we've collected, we've got some really good management practices ready to go."