Monday, November 13, 2006

Tracking N Use Efficiency with 15N Labeling of Corn.

Sharon Lachnicht Weyers1, Jane M.-F. Johnson1, Alan Olness1, C. Clapp2, Alan Wilts2, Jana Rinke2, and Nancy Barbour2. (1) USDA-ARS North Central Soil Consv., 803 Iowa Avenue, Morris, MN 56267, (2) 439 Borlaug Hall, USDA-ARS 1991 Upper Buford Cir, St. Paul, MN 55108

Nitrogen management is an important issue for economic and environmental sustainability. We designed an experiment in two phases 1) the growth phase to determine the impact of herbivore pressure on N uptake, and 2) the decomposition phase to determine recovery in a second crop from separately decomposing above and below ground residue. Canopy enclosures and insecticides were used to exclude herbivorous insects. We used 15N labeled ammonium sulfate as the initial fertilizer source of N for the first corn crop. 15N uptake and %N of plant tissue were greater under canopy exclosures than under open conditions; however, yields were still substantially higher under open conditions. During the decomposition phase greater %N in the decomposing tissue had an impact on final yield and net N mineralized during the growing season.