Elevated phosphorus study progressing in Maumee Watershed

By Matt Reese

Farmers do not enjoy spending money on nutrients to have them float down the creek. They also do not enjoy being the subject of the blame for water quality issues in Lake Erie. For years, Ohio agriculture has seen trends of decreasing phosphorus (P) application and increased conservation tillage, yet the water quality problems persist and in some cases seem to be getting worse. Why?

There are hundreds of potential factors from the watershed scale down to the specific zones of a single field that influence the answer to this question. One of those factors is the high P levels in portions of some fields from years of over application of nutrients. These elevated P zones are the subject of an ongoing study led by Jay Martin, an ecological engineering professor with The Ohio State University’s College of Food, Agricultural, and Environmental Sciences.

Martin said the study has four main parts: recruit the partner farmers; measure phosphorus runoff on the farmers’ fields; use and evaluate best management practices on the fields to reduce the fields’ phosphorus runoff while maintaining yields; and then form further public-private partnerships to expand the adoption of the practices throughout the watershed.

“The rationale for the project is that there is the assumption out there that fields with higher soil test P values disproportionally contribute to P runoff. One of the things this project is going to do is test this hypothesis and see if this holds true. A lot of the research would point to that fact, but to test that hypothesis there are a few barriers that have limited the ability to get practices to these types of fields. It is proprietary information about the soil test P levels and not many producers want to be identified as having one of these fields. One of our objectives here is to protect farmer anonymity,” Martin said. “The other unique feature of this project is working through crop consultants and nutrient service providers to find producers who want to be a part of this project. We have reached out to four nutrient service providers that operate in the Maumee Watershed. They have shared with us some P soil test levels and we can identify the best fields for us to monitor. Then they can reach out to those clients without us knowing who they are and they can see if they are interested in being proactive and doing this. That opens the door for us to start talking to those producers, share the expectations and see if their field makes sense for some of our monitoring and best management practices we want to install.”

If the farmer isn’t interested, “things end there, and no one finds out anything about their field that they didn’t know before we started,” Martin said. The participating farmers and nutrient service providers will be compensated. The study will pay for implementing and maintaining the management practices on the fields and will keep the farmer’s name and location confidential.

The study effort is seeking zones within fields with P soil test levels exceeding 100 parts per million, about 2.5 times the agronomic level.

“Beyond that we are looking for fields where we can put the best management practices either adjacent to that or on that field. We also have to have fields that are monitorable. Hopefully we have one drainage tile outlet from those high P zones. We have to collect water quality data to see how much P is coming off the field and how effective our practices are. We want to know about the tillage practices, application rate, crop rotation — anything that could impact the nutrients and water quality coming off the field,” Martin said. “One of the initial insights from this is that it is really not elevated P fields, it is elevated P zones within those fields. Less than 25% of the zones in these fields have elevated levels. That is a good insight. As we try to target management practices, we are trying to target those specific zones within the fields.”

One challenge in addressing high P zones is that the 4Rs of nutrient management — right source, right rate, right time and right place — do not really apply. In an elevated phosphorus situation, the farmer has probably already stopped applying additional phosphorus fertilizer.

“The 4Rs don’t really apply if we are not applying any P there. We need to find ways to manage that P leaking from those high P fields in a more effective way,” Martin said. “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 then offer recommendations for farmers and nutrient service providers.

They will be looking at both surface runoff and drainage water nutrient loss.

“It makes sense that if more P is in the soil, more will leach out through a drain tile than come off the surface,” Martin said. “But, with tillage you can stir up the soil and have surface runoff too. That is something we will test in this.”

This spring the researchers have visited about 25 to 30 potential fields and have some likely sites emerging.

“In the end, we need to have 12 new field sites, and we have a good chance of reaching this goal. We hope to have all sites in hand, and conservation practices installed before it gets too cold,” Martin said. “Presently, we are completing some initial designs to present to the farmers that we hope to work with. We will then meet with them to make sure they like what they see, and our future plans, before completing a final design. Likely practices include phosphorus filters, drainage water management, and constructed wetlands.”

The five-year, $5 million study includes partners and supporters from CFAES, the Nature Conservancy, the U.S. Department of Agriculture’s Agricultural Research Service (USDA-ARS), Ohio State’s Center on Education and Training for Employment, and 12 Ohio agricultural businesses and organizations. USDA’s National Institute of Food and Agriculture is funding the study, which started last fall and will run through summer 2023.

“I’m excited,” Martin said. “This is a way that the agricultural community, Ohio State and U.S. Department of Agriculture researchers, and nongovernmental organizations can work together to address an important unknown. By doing so, this will improve water quality while supporting agricultural production.”

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 and 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 USDA-ARS’s Soil Drainage Research Unit, the Nutrient Stewardship Council and the Ohio AgriBusiness Association.

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






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