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Is it working? A look at the changing nutrient practices in the Southern Willamette Valley’s Groundwater Management Area
Citation:
Pearlstein, S., J. Compton, A. Eldridge, A. Henning, J. Selker, Reneej Brooks, AND D. Schmitz. Is it working? A look at the changing nutrient practices in the Southern Willamette Valley’s Groundwater Management Area. Southern Willamette Valley Groundwater Management Area Website, Corvallis, OR, May 01, 2015.
Impact/Purpose:
In 2013, a partnership between federal, state and county agencies and local famers was established through an EPA Regional Applied Research Effort, to inform water quality and nitrogen management in the southern Willamette Valley Groundwater Management Area (SWV GWMA). The SWV GWMA was established in 2004 to address the occurrence of high groundwater nitrate concentrations exceeding the human health standard of 10 mg nitrate-N per liter. The RARE partnership project was developed to examine the current levels of nitrogen and phosphorus leaching associated with different crops and nutrient management practices in the GWMA. The team is studying common crops, using new and existing soil solution samplers called lysimeters. This information will be used to validate and calibrate the USDA APEX model development for the SWV. The information about nutrient losses and nutrient use efficiency associated with different crops and practices will also be shared with farmers, extension agents and crop advisers, in order to improve nutrient management in the area.
Description:
Groundwater nitrate contamination affects thousands of households in the southern Willamette Valley and many more across the Pacific Northwest. The southern Willamette Valley Groundwater Management Area (SWV GWMA) was established in 2004 to address the occurrence of high groundwater nitrate concentrations exceeding the human health standard of 10 mg nitrate-N L-1. Much of the nitrogen (N) inputs to the GWMA comes from agricultural sources and thus efforts to reduce N inputs to groundwater are focused upon improving N management. Previous work in the 1990s in the Willamette Valley by researchers at Oregon State University (OSU) determined the importance of cover crops and irrigation practices and made recommendations to the local farm community for reducing nitrate leaching from fields. We are sampling many of these original fields studied in the 1990s using existing soil sampling equipment, in order to examine the influence of current practices on nitrate leaching below the rooting zone. This study represents important crops currently grown in the GWMA and includes four grass fields, three vegetable fields, two each of peppermint and wheat fields, and one each of hazelnuts and blueberries. New nutrient management practices include slow release fertilizers and precision agriculture in some of the fields. Results from the first year of sampling in 2014 show that nitrate leaching is lower in row crops grown for seed and higher in others like perennial rye grass seed when compared to the 1990s data. We will use field-level N input-output balances in order to determine the N use efficiency and compare this across crops and over time. The goal of this project is to provide information and tools that will help farmers, managers, and conservation groups quantify the water quality benefits of nutrient management practices.