Some farm fields in northwest Ohio’s Maumee River watershed have more phosphorus than their crops can use. Called “elevated phosphorus fields,” such fields may be at higher risk of contributing to Lake Erie’s harmful algal blooms, according to an announcement from The Ohio State University.

That’s the premise of a new five-year, $5 million study that hopes to learn about those fields and lower that risk by creating new public/private partnerships.

Led by Jay Martin, an ecological engineering professor with The Ohio State University’s College of Food, Agricultural & Environmental Sciences (CFAES), the study plans to monitor and manage more than a dozen elevated phosphorus fields, all in the Maumee River watershed.

To do the work, the study is partnering with nutrient service providers — consultants who advise farmers on crop and soil matters, such as the types and rates of fertilizer to apply — and some of the farmers they work with. The nutrient service providers are working to find farmers to help with the study, while the farmers, in turn, allow their fields to be used as sites for the study.

“I’m excited,” said Martin, a faculty member in the CFAES department of food, agricultural and biological engineering and a faculty researcher with the university’s Ohio Sea Grant program and the Stone Laboratory. “This is a way that the agricultural community, Ohio State and U.S. Department of Agriculture researchers and non-governmental organizations can work together to address an important unknown. By doing so, this will improve water quality while supporting agricultural production.”

Maumee River watershed

Phosphorus runoff from farm fields is a significant driver of the harmful algal blooms plaguing Lake Erie, the announcement said. The blooms are sometimes toxic, are often many miles wide and threaten recreation, tourism, drinking water safety and people’s health. The Maumee watershed, which empties into the lake at Toledo, Ohio, is the lake’s largest source of phosphorus loading.

Martin said the study has four main parts: (1) recruit partner farmers, (2) measure phosphorus runoff on the farmers’ fields, (3) use and evaluate best management practices on the fields — practices aimed at reducing the fields’ phosphorus runoff while also maintaining their yields — and (4) then, by helping form further public/private partnerships, expand the adoption of the practices throughout the watershed.

The study includes partners and supporters from CFAES, the Nature Conservancy, USDA’s Agricultural Research Service (ARS), Ohio State’s Center on Education & Training for Employment and 12 Ohio agricultural businesses and organizations.

USDA’s National Institute of Food & Agriculture is funding the study, which started in September and will run through summer 2023.

Lake Erie algal blooms

Crops need the nutrient phosphorus to grow. It’s an important part of the fertilizers and manures farmers apply to their fields. However, rain can wash phosphorus out of the soil and then into drainage ditches, rivers and eventually Lake Erie.

In 2016, Ohio, Michigan and the Canadian province of Ontario agreed to reduce the phosphorus entering Lake Erie 40% by 2025. Experts think such a reduction will keep the lake’s blooms at safe levels. Ongoing efforts to meet that goal involve farmers, scientists and agencies, among others, the announcement said.

The new study, for its part, is specifically targeting elevated phosphorus fields, which bear that name because, after years of fertilizer or manure applications, they’ve accumulated more phosphorus in their soil than their crops need. The excess doesn’t hurt the crops; the crops just don’t take it up. However, sometimes, the phosphorus is released from the soil and ends up in Lake Erie, where it contributes to harmful algal blooms.

“The hypothesis is that these elevated phosphorus fields contribute disproportionately to nutrient runoff,” Martin said.

Until now, however, testing that hypothesis has been difficult. Locating an elevated phosphorus field requires soil test results, and those aren’t public information; they’re often kept only between a farmer and his or her nutrient service provider. The new study is solving that limitation by enlisting those individuals as partners.

New ways needed

In the Maumee watershed and other places, some farmers are reducing their phosphorus runoff by using the “4R” practices: the right source, right rate, right time and right place when it comes to applying fertilizer and manure, Ohio State said. However, the 4Rs don’t help on an elevated phosphorus field, because the farmer has probably already stopped applying additional phosphorus fertilizer.

Instead, other best management practices are needed — ones that keep nutrients in the field or that trap them at the edge of the field before they get into waterways.

Martin said the study will implement a variety of best management practices at the study sites and then will evaluate the practices using edge-of-field water sampling. The practices may include building wetlands, growing cover crops and installing phosphorus filters, among others. Based on the findings, the study will offer recommendations for farmers and nutrient service providers.

Other CFAES researchers involved in the study are Margaret Kalcic, Ryan Winston, Mike Brooker and Nathan Stoltzfus of the department of food, agricultural and biological engineering; Robyn Wilson of the School of Environment & Natural Resources; Greg LaBarge of Ohio State University Extension, and Brian Roe of the department of agricultural, environmental and development economics.

Key partners on the study also include Jessica D’Ambrosio of the Nature Conservancy, Kevin King of the ARS Soil Drainage Research Unit, the Nutrient Stewardship Council and the Ohio AgriBusiness Assn.

Collaborating on the study are four northwest Ohio nutrient service providers — Nester Ag, Legacy Farmers Cooperative, Nutrien Ag Solutions and the Farmers Elevator Grain & Supply Assn. — as well as the following organizations: Ohio Corn & Wheat Growers Assn., Ohio Soybean Council, Ohio Pork Council, Ohio Dairy Producers Assn., Mercer County Community & Economic Development and Ohio Farm Bureau Federation.