Dr. Jennifer Blesh, Assistant Professor, University of Michigan, Department of Ecology and Evolutionary Biology.
Agroecosystem management and nitrogen balance on grain farms in the Midwest
ABSTRACT: Human alteration of the global nitrogen (N) cycle, particularly through agricultural production, has led to persistent environmental consequences. For example, soluble N forms leach to surface waters and are transported to coastal marine ecosystems causing eutrophication and hypoxia. This seminar will explore how applying ecological theory to N management can tighten agroecosystem N cycling, using research on farms in the upper Mississippi River Basin (MRB) as a case study. Nitrate losses from grain farms in this region are a primary contributor to the annual hypoxic zone in the Gulf of Mexico. Nitrogen mass balances were constructed for a range of farm management types—from corn-soybean rotations to diversified farms that rely on legume nitrogen fixation as a primary N source—in four states in the upper MRB: Iowa, Minnesota, Ohio and Wisconsin. The N balance approach combined data from farmer interviews with analysis of grain and legume samples, and measurements of legume N fixation. Practices that increase carbon sinks for inorganic N, and support the rhizosphere processes that supply N through the soil N cycle, can reduce surplus N additions. This research also addressed how a subset of farmers had transitioned to practices that the N balance study indicated have the greatest potential for reducing N loading to the Gulf of Mexico, focusing on the resources and strategies that farmers mobilized to develop opportunities for innovation.
11:30 AM - 12:15 PM
244 Kottman Hall (Columbus)
121 Fisher Auditorium (Wooster)