Science of Water Monitoring

Anthony Seeman and Corey McKinney draw samples of water from a tributary of the Middle Cedar River to test for nutrients, dissolved oxygen and suspended solids.

Science of Water Monitoring: ISA Lab Trusted Source of Data

BY CHRIS HAY AND ANTHONY SEEMAN

The Iowa Soybean Association (ISA) has been monitoring water quality for over a decade. The monitoring program has evolved over time and includes rivers, streams, individual tile outlets and edge of field practices located throughout Iowa.

Water samples are analyzed in ISA’s certified water laboratory. The lab serves as a trusted source of water quality data for soybean farmers. Data is provided to participating farmers to help inform their management decisions. When aggregated with data from other farmers, it’s used to gain insight into impacts of management on water quality to make recommendations for improvement for all farmers.

ISA and its partners also use this data to target areas for planning and implementing water quality projects and to evaluate the effectiveness of installed practices.

Monitoring with Agriculture’s Clean Water Alliance, a consortium of ag retailers and support companies in the Des Moines and Raccoon river basins and ISA partner, showed that nitrate-nitrogen concentrations in the Boone and Raccoon Rivers in 2019 were some of the lowest since monitoring began. While low concentrations are good, they often occur with higher river flows, and the overall loss of nitrogen, measured as load (concentration multiplied by flow) is still high from the greater volume of water transporting nitrogen. In 2019, however, nitrate concentrations were low enough that nitrogen loads remained moderate despite higher than average river flows.

The interactions among soil, weather and management that influence nitrogen loss are complex. However, the 2019 results suggest that the cooler and wetter spring that delayed planting also delayed nitrogen mineralization into water-soluble nitrate that was available for loss early in the spring when nitrate concentrations are usually highest.

The Miller Creek Water Quality Initiative (WQI) project is one of several WQI projects funded by the Iowa Department of Agriculture and Land Stewardship within the Middle Cedar River watershed in eastern Iowa. It provides an example of the impact of ongoing conservation practice implementation on water quality in a smaller watershed.

The project focuses on reducing nutrients leaving farm fields through voluntary adoption of practices outlined in the Iowa Nutrient Reduction Strategy (INRS). Water quality monitoring has been conducted with the project since April 2014. Sampling is focused on both streams and individual field tile outlets to monitor overall conditions in the watershed and give producers a look at the impact their management is having on water quality.

The Iowa Soybean Association has been monitoring water for over a decade.

Nitrate concentrations in Miller Creek have generally been declining since monitoring began in 2014, and the average nitrate concentration in 2019 was the lowest yet. Nitrogen yield (pounds of nitrogen lost per acre), however, has been more variable because of the impact of weather on nitrogen load and yield. Another positive sign is that the average nitrate concentrations of the individual tile outlets monitored over the life of the project have consistently declined. These results illustrate the interaction between nitrogen loss and weather. Nitrate concentration reductions are good, but they will sometimes be counteracted by greater flow in wetter years when it comes to overall nitrogen loss. The short time period for the project makes it difficult to draw strong conclusions. However, the results suggest that things are at least moving in the right direction.

Denitrifying woodchip bioreactors are one example of the water quality practices in the INRS for reducing nitrogen loss. Bioreactors work by diverting water from a tile drainage system through a trench filled with woodchips before it outlets to a stream, ditch, or tile main. Microbes in the woodchips convert nitrate in the drainage water into nitrogen gas that is released back to the atmosphere, reducing the amount of nitrate in the drainage water.

Blake Hollis of Lanehaven Farms installed a bioreactor in 2014 as part of the Miller Creek WQI project. Water quality monitoring of flow into and out of the bioreactor has been used to monitor the performance of the bioreactor over time. Average nitrate concentration reductions from the bioreactor have been 40% since it was installed. In 2019, nitrate concentrations were reduced by 51% on average.

“Participating in the Miller Creek watershed project and ISA water monitoring project have certainly helped me gain a greater understanding of my footprint and need to engage in water quality improvement,” says Hollis.

Results for the Hollis bioreactor show the impact that adoption of water quality practices can have at the scale of an individual field.

“Any time you change practices, there's a learning curve involved,” says Hollis. “Every operation is different, with various goals and constraints, so when it comes to conservation there is usually not a ‘one-size-fits-all’ solution.”

Although it’s too early to know the long-term impacts of watershed projects like the Miller Creek WQI, the early results are encouraging and show some improvement in water quality. It will take much greater adoption of individual water quality practices and sustained efforts at the small watershed scale with projects like the WQIs to begin to reverse the long-term increase in nitrogen loads at a scale like the Raccoon River to meet the goals of the INRS. Data from the ISA water lab will continue to be important to target efforts and measure progress.

For more details on the 2019 monitoring results, see the three-part “2019 Water Quality Summary” series in the ISA Newsroom.