Where the Soil Water Flows: Working with Southern Willamette Valley Farmers in the Groundwater Management Area

By Susanna Pearlstein | July 6, 2015
One of the lysimeter study's control fields. © S. Pearlstein
One of the lysimeter study’s control fields. © S. Pearlstein

Buzzzzzz…..ping, ping….Ping!Ping!Ping! I would like to say I handled getting stung in the face repeatedly with composure. I did not. Anyone watching would have seen a grown woman suddenly clutch her face, scoot away from a cluster of hives and sprint down a soft dirt road, kicking up a wash of dust and profanities into the cloud of honeybees trailing her. Welcome back, summer!

The minor pain was a clear reminder of the hard work taking place above ground. These ladies fiercely represent the 15 billion dollar national industry* of commercial bee pollination, and were keeping the pea field I’d come to visit in booming, blooming business.

Why was I at the farm that day? It wasn’t just to look at bees. The farmer renting those hives had generously opened his doors to me and the project I work on the year before, allowing us to install water samplers, known as lysimeters, to collect soil water moving below the crop root zone on three of his commercial fields. My project, Partnership to Improve Nutrient Efficiency, is funded by the Environmental Protection Agency (EPA) coupled with support from the Oregon Department of Agriculture’s (ODA) Fertilizer Grant and the Oregon Department of Environmental Quality (ODEQ) water chemistry lab.

The kind, pea-growing, bee-hosting farmer isn’t the only one in the valley allowing us to do this. Throughout Benton, Linn, and Lane counties a total of 11 commercial farmers also let us collect soil water samples from their farms weekly. In these fields grow crops that represent the current diversity of southern Willamette Valley farming from grass seed and wheat to filberts, peppermint, vegetables, and blueberries.

Southern Willamette Valley Groundwater Management Area
Southern Willamette Valley Groundwater Management Area

All of these lysimeter fields are located in the southern Willamette Valley’s Groundwater Management Area (GWMA, pronounced “gwah-mah”) where the groundwater contains high amounts of nitrate-N in some areas. Nitrate is a contaminant which can interfere with blood oxygen supply after drinking the water, especially in babies younger than six months. If you’ve ever heard of blue baby syndrome, that’s from nitrate contamination, and it’s the reason we have a human health drinking water standard for nitrate of 10 milligrams of nitrate-N per liter. Nitrate in groundwater is a concern in the GWMA because many people use private groundwater wells for their drinking water. Boiling does not remove nitrate, it can only be removed by special filters.

A GWMA is established by ODEQ to identify an area in the state where there is large scale non-point source groundwater contamination. “Non-point source” describes areas where the contamination doesn’t come from one identifiable place. Rather, it can originate from several places, like water draining from a farm field or a septic tank. Before the southern Willamette Valley GWMA was started, researchers at OSU worked with farmers in Lane County in the 1990s doing similar measurements with lysimeters. This pioneering work established relationships with many farmers who work with us today and helped us begin to understand how agricultural practices influence nitrate-N leaching. We use the 1990s data to see how agricultural practices in the GWMA have changed over time. The lab results from our current study are compared with the 1990s data and new data gathered from farmer interviews to see how the nitrate-N leaching amounts relate to the timing of fertilizer applications, local weather patterns, site soil type, and the life stage of the crop. Once nitrate is in the groundwater, it stays there for years to decades, so the goal is to keep the nitrate in the crop and rooting zone.

Teresa Matteson conducting a very fresh post-harvest soil sample. © S. Pearlstein
Teresa Matteson conducting a very fresh post-harvest soil sample. © S. Pearlstein

The soil water we take from the fields is tested for nitrate. We are also lucky to have Benton SWCD’s very own Teresa Matteson conducting soil analysis at all of the fields in the spring and fall. All the data from this study is made available to the farmers, but kept anonymous to others. The farmers use the data to see how much of the nitrogen fertilizer they apply is leaking below the rooting zone rather than going into the crop and to inform their cropping practices.

This project is like a colony of bees. Each collaborator has a different, well-defined job, essential to keep the project humming along. The most important collaborators are the farmers – without them the project would not happen. I am always humbled by their generosity as they take time out of their busy day to talk me through their practices, plans for the future, lessons from the past, and insights into the farming world.

Each day I’m looking less like the Elephant Man as my bee sting welts heal. The blossoms in the pea field are past their peak but the bees are still there, foraging within two miles of the hives and helping the farm lands around them use nitrogen and turn water, other soil nutrients, air, and sunlight into the very food we eat. I like bees so much because they are easily overlooked – a tiny workforce you barely notice carrying on with single-minded focus. Even smaller than the bees, a molecule of nitrogen is added, cycled and used by plants in a very quiet but important way, one that is also easy to overlook. We are trying to capture this essential process at the local scale and identify any practices that are more efficient, meaning they could reduce nitrate leaching to groundwater. It is our hope we will be able to provide useful, locally-derived data that can be turned into a tool that farmers, managers, and conservation groups can use to quantify the water quality benefits of their farm practices and use that information to continue to grow the diverse set of crops found in our valley while protecting our drinking water.

Learn More about Nitrate and GWMAs

Project Partners


Sagili, R.R., Burgett, D.M., 2011. Evaluating Honey Bee Colonies for Pollination: A guide for Commercial Growers and Beekeepers. Pacific Northwest Extension Publication.

About the Author

Susanna Pearlstein

Susanna works as a Post-Doctoral researcher with the US Environmental Protection Agency and a water quality specialist with Benton Soil & Water Conservation District where she is partially funded by the Oregon Department of Agriculture Fertilizer Grant. Susanna is a small scale bee keeper and hasn’t (yet) been stung by her own bees. When she is, she sincerely hopes it’s not in the face.

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