Nitrogen addition is a cornerstone of modern agriculture, but fertilization has impacted inland and coastal waters by increasing nitrogen concentrations, supporting excessive growth of aquatic plants, reducing oxygen concentrations, and triggering harmful algal blooms. Because of extreme drought in 2012, Midwestern soils have accumulated nitrogen that is expected to be driven into river networks by late summer or fall precipitation. This anticipated landscape-wide nitrogen pulse offers an immediate and unparalleled opportunity to record how nitrogen enters streams, and to quantify the transport, attenuation, and fate of nitrogen as it moves through stream networks. An existing stream monitoring network will be expanded and used to collect water samples during and after major precipitation events in fall 2012, taking advantage of a short-term opportunity to characterize nitrogen movement and processing in an agricultural landscape. Unintended consequences of fertilization are an increasingly important issue for resource managers. This project will add to our understanding of how nitrogen moves from agricultural lands into and through stream networks, and it will do so under climate conditions that are expected to be more common in the coming decades. Additionally, this project will support five early career scientists and a collaboration between the University of Nebraska-Lincoln, the University of Iowa, and Coe College. Inclusion of Coe College will provide opportunities for undergraduate research and mentoring of undergraduate students by faculty and graduate students.
Agricultural fertilizers impair water quality by increasing river nitrogen (N). We determined that the amount of N entering rivers in agricultural areas is controlled by drought-to-flood transitions, termed weather whiplash. Weather whiplash includes increased summer droughts and heavy subsequent spring rains, similar to the 2012-2013 record Midwestern U.S. drought-floods. Weather whiplash events are predicted to increase with a changing climate; thus, climate change will likely cause further deterioration of water quality in agricultural regions. Unchecked, this interaction between climate change and agricultural management may create a positive feedback loop that motivates farmers to apply more fertilizer to offset leaching losses. This award contributed to building scientific capacity by training a female post-doctoral associate, two female Master's students, and providing research experiences to over a dozen undergraduate students, many of whom are first generation college students. Both Master's students and many of the undergraduates presented their findings in numerous poster and oral presentations. We also developed our findings into four manuscripts either published or nearing publication, with an estimated 2-4 additional manuscripts to come from the rich dataset collected herein. Finally, we engaged the public in our findings by transmitting them via mass media, including the Iowa Public Radio show, River to River, and a feature article on our project printed in the Cedar Rapids Gazette.
