Enhanced Efficiency Nitrogen Fertilizer: Potential Impacts on Crop Yield and Groundwater in Tall Fescue Fields of the Southern Willamette Groundwater Management Area, Oregon, USA
Citation:
Williams, T., J. Derksen, J. Compton, AND J. Morse. Enhanced Efficiency Nitrogen Fertilizer: Potential Impacts on Crop Yield and Groundwater in Tall Fescue Fields of the Southern Willamette Groundwater Management Area, Oregon, USA. AGU, San Francisco, CA, December 09 - 13, 2019.
Impact/Purpose:
Portland State University scientists Dr. Jen Morse and Trevor Williams, along with OSU graduate student Jake Derksen, are conducting a study examining the broad benefits of enhanced efficiency fertilizers for decreasing nitrate leaching and greenhouse gas emissions while maintaining agronomic yields. EPA scientist Jana Compton is advising on the nitrate leaching component of the study. This study is working collaboratively with fertilizer industry staff and local farmers to test their products in tall fescue grass seed fields. The results indicate there were no consistent effect of the slow release fertilizer product on leaching or seed yield. Continued analysis of the data at a systems level will provide more insights into the best practices for application of N fertilizers in order to mitigate their environmental and human health impacts.
Description:
Synthetic nitrogen (N) fertilizers have greatly increased global agricultural productivity since the mid-19th century, but their inefficient use potentially diminishes water quality and negatively impacts human health. When high application rate is combined with environmental factors like low temperature or excessive precipitation, plants do not completely assimilate N, which can lead to leaching and runoff, contributing to excessive nitrate in drinking water. Parts of the Southern Willamette Valley, Oregon, have been designated a Groundwater Management Area for this reason. Here, high rates of nitrate leaching have been associated with multiple crops, including grass seed grown for turf and animal grazing, an important agricultural product in this region. Fertilizer products with physical or chemical inhibitors that slow the release of plant available N into the soil (enhanced efficiency fertilizers) have been offered as a solution to optimize uptake and decrease runoff and leaching. To further inform efforts to increase efficiency and sustainability in nutrient management practices, our study compared grass seed yield, soil solution N concentrations, and residual soil N after harvest in four tall fescue (Lolium arundinaceum (Schreb.) Darbysh.) grass seed fields under one acre plots with conventional or enhanced efficiency N fertilizer (NutriSphere-N® coated urea pellets) treatments. Soil water solutions were collected from 4 lysimeters, 1 meter under each treatment plot, biweekly for two growing seasons (2018-2019), and analyzed using colorimetry for ammonium and nitrate concentrations. Soils (0-15 cm) were collected and analyzed to characterize soil physical and chemical properties, soil N content, and potential microbial N cycling rates. Soil temperature, moisture, and precipitation data were also collected daily for the duration of the study. We found that enhanced efficiency N fertilizer had mixed effects across the four fields that varied in soil type and N application rates and timing. Enhanced efficiency N fertilizer did not consistently decrease N leaching or increase seed yield. Water and soil analyses, along with crop and environmental data, together can aid in establishing best practices for application of N fertilizers in order to mitigate their environmental and health impacts.