Through experiments conducted on 20 fields across Ohio, researchers tested the benefits of side-dressing manure. They also evaluated the role of soil health in reducing corn crops’ demand for nitrogen. Over two years, the team analyzed more than 400 soil samples, 800 plant tissue samples, 16 manure samples, and 120 water samples. Aerial photography from drones provided additional insights into plant health and growth.

Findings indicate that manure applied as a side-dress, compared to conventional nutrient application using fertilizers, increased or maintained similar levels of nutrient concentration in corn tissue. Side-dressing manure into growing corn resulted in a significant increase in corn yield by 13% across 12 trials. Other experiments showed that fields with regular manure applications can reduce total nitrogen application requirements.

Additionally, comprehensive analysis of water quality data confirmed similar nitrogen and phosphorus losses between manure and conventional fertilizers, reinforcing the benefits of manure applications. Soil health indicators were found to be reliable predictors of nitrogen inputs, and economic evaluations demonstrated the cost-effectiveness of these practices.

As a whole, the project provided strong evidence supporting the use of side-dressed manure as a sustainable and efficient method for improving corn growth, soil health, and farm profitability all while mitigating nutrient losses. Notably, through the team’s collaborative efforts, participating farmers were able to implement sustainable agricultural practices that significantly improved soil health on their land.

Here, researchers investigated how water moves through soils in wetlands, developing innovative ways to trace the movement of water within the subsurface. Rather than using traditional soil sampling and analysis, the team deployed geophysical methods — including electromagnetic imaging, electrical resistivity tomography, and ground penetrating radar — to map large areas of wetland like an X-ray. Researchers tested a new method of tracing how water flows through wetland soils by releasing rainwater, slightly heated water, and water with increased electrical conductivity. They also developed a numerical framework that can simulate water flow within wetland soils.

The team has begun implementing these methods at Oakwood Nature Preserve in Findlay, OH installing 30 soil sensors and seven groundwater monitoring wells to track water movements. Initial results characterized the clay, silt, and sand content of the soil. Notably, researchers found that these sediments change dramatically with soil depth and can hold and allow subsurface water flow in some areas. This suggests that site managers should pay more attention to soil types and properties, as well as how they vary spatially and with depth, when constructing and restoring wetlands.

Broadly, results will help ensure wetlands retain and prevent nutrients from leaching into open water bodies, particularly Lake Erie. The use of geophysical data will make wetland monitoring less expensive and more efficient. Tracing subsurface flow will improve the selection of sites for restoration and also inform decisions on managing restored wetlands to ensure they are continually serving as nutrient sinks. In addition, the numerical simulation is key to being able to assess nutrient retention within wetlands.

To remedy this, researchers worked with a startup water sensor company to help develop and test a new technology that could analyze these important nutrients and revolutionize water quality analysis. Using polymer technology licensed from The Ohio State University and water quality data from the National Center for Water Quality Research, the company produced ionic sensors that are selective to conditions in Ohio watersheds. Then, researchers assessed water samples from various tributaries using both standard laboratory methods and the new sensors.

The team validated that the ionically selective sensors can detect pH and low levels of NH₄, with results comparable to laboratory analysis. Development of a sensor to detect orthophosphate, a DRP equivalent, is almost complete. While the product is not yet field-deployable, the team made significant progress toward reaching that goal.

The sensors offer a number of benefits: they aren’t affected by other particles in the water, are made of relatively inexpensive materials, and can manufactured for multiple uses by being built in different shapes and sizes. Once development is completed, the sensors could be deployed on-site at crucial points at field edges, throughout rivers, and ultimately in Lake Erie. Hopefully, this technology will help decision-makers, both elected officials and agencies, address HABs in a highly robust and accurate manner.

To identify major contributors to algal blooms, researchers can analyze manure from livestock operations and look for patterns. However, existing analytical methods, such as genomic sequencing, are cost prohibitive and generally unreliable when it comes to identifying specific livestock species. Recently, a team of researchers found stable isotype analysis to be a promising new method of tracing nutrient sources. With their latest study, they aimed to determine whether this emerging technology can differentiate among manure sources and locate nutrient “hotspots.”

Researchers put this method to the test by first collecting manure samples from livestock operations within the Grand Lake St. Marys watershed. Then, they examined the ratios of oxygen isotypes in inorganic phosphate molecules in the manure, making comparisons among them as well as with data in established literature. The team also collected stream samples from Chickasaw Creek and other waterways that empty into Grand Lake.

An assessment of different types of agricultural manure from across the watershed indicates statistically significant differences among their isotopic signatures, researchers found. This finding encourages further development of isotopic methods as a way to trace nutrient sources. Researchers also plan to evaluate which of the previously analyzed manures may be contributing to each of the stream locations sampled. Results from the project have contributed to the growing database of isotopic ratios related to nutrient sources in bodies of water. The findings will hopefully lead to more “focused” management and mitigation efforts across the region.

The project was a collaboration among teams of researchers at The Ohio State University, The University of Toledo, and the U.S. Department of Agriculture (USDA) Agricultural Research Service, each respectively focusing on watershed modeling with the Soil and Watershed Assessment Tool (SWAT), mapping crop management data through remote sensing, and monitoring conservation effectiveness. Researchers improved watershed modeling by updating a variety of regional data: high-resolution remote sensing crop management data, animal facility locations and numbers, soil phosphorus values, and flow and water quality data from field edges and river gage sites. The teams then used this improved model to validate top management practices in the region and evaluate their water quality benefits.

Researchers successfully mapped conservation practices, improved the SWAT model, and assessed the effectiveness of conservation practices to inform future statewide efforts. The project also addressed the potential of these practices to achieve a 40% reduction in phosphorus inputs to Lake Erie from 2008 levels. Importantly, the work identified conservation practices with the greatest potential to reduce nutrient runoff to improve water quality in agricultural watersheds.

The team established five monitoring stations to compare the removal efficiencies of three distinct treatment zones — a wintering pool, an attenuation wetland, and a meandering treatment wetland — as well as the wetland as a whole. The monitoring locations contain flow meters and automatic samplers that quantify the amount of nitrogen, phosphorus, and sediment removed. Researchers took measurements during wet weather events at each location and analyzed for nutrients. The team also worked to model wetland flow, estimate the cost effectiveness of the wetland, and sample soil and vegetation.

The researchers’ monitoring setup has enabled flow-based water quality sampling, which has already proven to be useful in measuring the wetland’s ability to treat nutrient runoff. After drought conditions persisted during the first year of monitoring in 2023, the team was able to collect hydrology and water data for eight storm events in early 2024. Results showed significant removal of sediment, sediment-bound phosphorus, dissolved phosphate, total nitrogen, and various forms of nitrogen.

Data collected from this wetland will help inform how nutrients are abated in riverine floodplain wetlands, optimize wetland hydrologic conditions, and inform wetland function during flooding events so that the system could be mimicked along other major rivers across Ohio. The project has shown an ability to improve the water quality of the EFLMR and the downstream William H. Harsha Lake. The wetland has and will continue to provide stakeholders with operation, maintenance, and performance data to help select the best water quality treatment methods for floodplain environments.

To quantify this, the team worked to conduct a formal analysis of self-forming ditches, compared to prior “twostage” designs, at nine sites around Ohio. Self-forming ditches were constructed in past years by widening the area around the channel to create a floodplain, allowing water to interact with vegetation and sediment to create its own stream system. Researchers measured repeated cross sections of the channels, of both types, to see how fast sediments were building up and what nutrients were being stored.

Analysis showed that across all the sites, the ditches accumulated a little less than an inch per year of sediment, and self-forming sites trapped significant amounts of nutrients in particular. Based on researchers’ predictions, the systems should trap material for multiple decades in most cases. Notably, the team found that retention rates of nutrients in the ditches were comparable to that of natural and constructed wetlands. Researchers also found that rates of nitrogen and phosphorus mineralization — a long-term process where nutrients are converted to their inorganic forms and can eventually release into the environment — were relatively low.

These findings can help farmers understand the benefits of using conservation ditch designs, including self-forming and “two-stage” designs, over conventional ditches to benefit ecosystems and society as a whole. In the future, the team hopes to expand the research to include more sites with agricultural drainage ditches. Future research could also study the possibility of using trapped materials from ditches as a fertilizer alternative or soil amendment.