River monitoring programs by Heidelberg College’s National Center for Water Quality Research have documented a fourfold increase in the movement of a particular kind of phosphorus from cropland into Lake Erie over the past 10 years.
“This form of phosphorus, which is dissolved in runoff water, is very effective in stimulating the growth of harmful algae in Lake Erie,” said David Baker, director emeritus of the lab. “The impacts of this runoff are especially evident in the bays and nearshore areas of Lake Erie where excessive growths of blue-green algae have become a major concern.”
The Great Lakes Protection Fund has awarded the lab a $940,000 grant to lead an effort to reduce dissolved phosphorus runoff from the Sandusky River Watershed into Sandusky Bay and Lake Erie. “One goal of the project is to achieve at least a 30 percent reduction in dissolved phosphorus runoff during the next five years,” said Baker, who authored the grant proposal. “Another goal will be to ‘export’ the lessons learned in the Sandusky Watershed to other agricultural areas in the Lake Erie Basin, as well as other Great Lakes states.”
The increase in dissolved phosphorus runoff from cropland comes at the same time farmers have made major progress in reducing particulate phosphorus runoff from their fields. Particulate phosphorus is attached to eroded soil particles. Its runoff has been reduced through farmer adoption of various erosion control techniques, such as reduced-till and no-till crop production.
“It’s interesting. One of the causes of increased dissolved phosphorus runoff is apparently the same no-till and reduced-till cropping practices that reduce particulate phosphorus runoff,” Baker said, adding that with no-till and reduced-till, phosphorus accumulates at the soil’s surface. Part of the accumulation is associated with surface applications of phosphorus fertilizers and manures.
In addition, crop roots take up phosphorus from deeper in the soil. When the stems and leaves are left on the soil surface to protect the soil from erosion, they eventually decay, depositing their phosphorus deeper into the soil. With no-till and reduced-till, the soil is no longer inverted so that phosphorus continues to accumulate on the soil surface. “It’s the phosphorus concentration at the soil surface that determines dissolved phosphorus concentrations in surface runoff,” Baker said.
Much of the grant funding will subsidize stratified soil testing in the Sandusky Watershed. “In normal soil testing, a sample is taken that looks at the entire upper 8 inches of soil,” said John Crumrine, the lab’s agricultural project coordinator. “In stratified soil testing, we will be dividing the soil column into three portions – 0-2 inches, 2-4 inches and 4-8 inches – with separate testing for each portion.” With a grant from the Lake Erie Protection Fund, Crumrine has led a pilot project of stratified soil testing in the Rock Creek Watershed. Preliminary results from that project confirm the build-up of phosphorus in the upper 2 inches of the soil.
The Heidelberg researchers have assembled a 34-member project team to help address the problem. The team is comprised of local farmers, certified crop advisers, fertilizer dealers and representatives of local soil and water conservation districts, soil testing labs, extension offices and state and federal agencies, as well as faculty from The Ohio State University.
“We believe that with the stratified soil testing data, fertilizer application data and the use of current fertility guidelines, the project team will be able to identify several opportunities where we can link economic savings for farmers with reduced soluble phosphorus export to Lake Erie,” Baker said.
The project team also includes members from the University of Wisconsin, Michigan State University and the Ontario Ministry of Environment. “These participants will bring their experience with soil testing and phosphorus runoff to our program and convey the lessons learned in the Sandusky Watershed to their own locations,” Baker said.
This latest grant will be completed in conjunction with the Honey Creek Targeted Watershed Program, a $900,000 grant the lab recently received from the U.S. EPA. Results from both grants will support the programs of the Ohio EPA’s recently formed Ohio-Lake Erie Phosphorus Task Force, which has been meeting for several months to address the issue of increasing dissolved phosphorus runoff to Lake Erie.