By Dusty Sonnenberg, CCA, Ohio Field Leader, a project of the Ohio Soybean Council and soybean checkoff
Since 2011, the algal bloom on Lake Erie has garnered much attention. The general public that uses the lake for recreational purposes, and the tourism industry and the media are quick to point the finger at agriculture as the primary contributor to the problem. The Western Lake Erie Basin is fed by rivers that drain nearly 7 million acres of farmland. The Maumee River Watershed (which contains the Blanchard River) flows into the Western Basin of Lake Erie. Phosphorus and Nitrogen in the river water are considered a contributor to the growth of the algal bloom each year.
“The harmful algal bloom (HAB) on Lake Erie has been a problem because the lake serves as the primary drinking water source for the City of Toledo. The HAB can produce toxins that can cause liver damage if the concentration is high enough,” said Greg LaBarge, OSU Extension Field Specialist, Agronomic Systems. “The relatively shallow depth of the lake, which going out to the islands is about 24 feet on average, warms quickly and allows the bloom to grow when conditions are right. The bloom floats on top of the water and depending on the wind direction the bloom can blow into where the city’s water intake is located. This is what happened in 2014.”
Phosphorus (P) and Nitrogen (N) in the river water are the primary focus of concern. P and N come from many sources. When water quality is measured and reported, the three primary sources of N and P considered include: home sewage treatment systems, National Pollutant Discharge Elimination System (NPDES) which are EPA permitted facilities, and then non-point source pollution. Non-point source pollution may be considered by many to be strictly agricultural, but in reality, non-point source pollution is anything not included in home sewage treatment and NPDES. Non-point source is anything that can not be tied directly back to a pipe or specific point-source.
“Non-point source could be a stream bank that is eroding, it could be a construction site that has rain run-off, it could even be a pipe that is not on a map,” LaBarge said.
The reason the agriculture industry has invested so much money and is studying this issue is because it has been considered the catch-all for everything non-point source. The United States Department of Agriculture (USDA) Agricultural Research Service (ARS) in conjunction with many universities is conducting water quality research through edge of field studies.
“Dr Kevin King is the lead here in Ohio conducting the research,” LaBarge said. “There are 20 sites (40 fields) across the state being monitored similar to what is being done at the Blanchard River Demonstration Farms Network sites. The fields are being monitored separately for the surface water runoff and subsurface drainage water. Samples are collected during and after any rain events. The amount of water and concentration of what is in that water is being measured and recorded all year long.”
Total phosphorus loss is being monitored in this edge of field study. There are two categories of P loss that are recorded. The first is DRP.
“DRP is dissolved reactive phosphorus, which is the soluble P that is the portion that is available to the plant roots and used by plants. It is also the P the leaks out and goes down the tile drainage system,” LaBarge said. “The second category is the surface run-off water containing phosphorus on the soil particles that erode.”
The Great Lakes Water Quality Agreement is an international agreement that was signed in 1972 between the United States and Canada to restore and protect the waters of the Great Lakes. It provides a framework for identifying priorities and implementing action to improve water quality. It determines a certain quality level target to be reached.
“The research is showing that only tenths of a pound of P per acre are being lost on most fields monitored,” LaBarge said. “The average loss of .27 pound P per acre is the target. Many of the sites monitored are below that target. A few fields are above the target. The average loss of DRP across all sites is .4 pounds per acre. (DRP is a portion of Total P.) The average total P loss across all sites monitored is 1.3 pounds per acre.”
The next step in the research is to identify conservation practices that are realistic to implement and will be “directionally correct.”