Setting Nitrogen Surplus Benchmarks to Control Nitrate Pollution of Groundwater in Northeast Nebraska

By Gabrielle Boucher, NWC student intern

Every year, the Nebraska Water Center (NWC) awards United States Geological Survey (USGS) 104b funding for projects intended to address water challenges in Nebraska. The competitive selection process includes reviews by a panel of fellow colleagues. This year, four projects were chosen and each focuses on contaminated water in Nebraska. To provide an overview of each project and the researchers behind them, the NWC will publish a series of articles on 104b awardees.

With the high volume of farming in Nebraska, nitrate levels in groundwater have been an issue for quite some time as agriculture has contributed high concentrations of this contaminant. Even with efforts to control concentrations from various organizations such as Natural Resource Districts (NRDs) and Nebraska’s Department of Environment and Energy (NDEE), nitrate levels are still on the rise. This is perplexing because multiple policies and technologies to reduce contamination have so far been unsuccessful. Dr. Mesfin Mekonnen believes it is vital to conduct research on sources of contamination in order to create improvements concerning the control of nitrate concentrations in Nebraska.

Mekonnen is a research assistant professor with the Daugherty Water for Food Global Institute. He is originally from Ethiopia and has been in Nebraska for four years. He is excited to be leading a project titled “Setting Nitrogen Surplus Benchmarks to Control Nitrate Pollution of Groundwater in Northeast Nebraska” with the grant he has received. The focus of this project is to evaluate sources of nitrogen besides that from fertilizer. Mekonnen noticed a gap between the amount of research on fertilizer- based nitrogen and non-fertilizer sources, so he is seeking to answer whether significant nitrogen contamination comes from sources other than fertilizer. The research completed for this project will estimate nitrogen input and output from various sources in four northeast Nebraska NRDs.

So how does he propose to measure this surplus? For context, nitrogen surplus is defined by Mekonnen as the difference between the amount of nitrogen coming in and going out. In some places the surplus could be negative, but here in Nebraska, it is typically positive. For this research, nitrogen surplus will be evaluated in rural areas by determining the input of nitrogen from fertilizers, manures, deposition, fixation, and irrigation water as well as outputs from harvested crops and grass, crop residues, and gases. This contrasts with other research that focuses only on fertilizers. The novelty of this study will hopefully give a broader idea of where nitrogen contamination comes from in Nebraska. 

Mekonnen expects results to show “nitrogen fertilizer application will be the major problem, but he can also see an input from manure plus what we don’t consider in most cases – rural places that use septic tanks.” This will hopefully extend beyond meeting research objectives and deliver information that can be used to conserve resources and protect Nebraska. Ultimately, this project can be something that inspires other researchers to look into these ideas.

This project will begin on March 1, 2020 and results are expected within one year. Mekonnen will be working alongside Dr. Daniel Snow, director of the University of Nebraska-Lincoln’s Water Sciences Laboratory and Dr. Dan Miller, USDA-ARS research microbiologist.