Nitrous Oxide Emissions across a Nitrogen Fertilizer Gradient in Production Scale Corn Fields

While the relationship between nitrous oxide (N₂O) flux and crop management is complex, the amount of N applied can greatly influence the resulting N₂O emissions.  Previous research demonstrated the potential to significantly reduce N₂O emissions from agricultural soils by reducing N fertilizer inputs.  Further, environmentally significant reductions in N₂O emissions may be possible with relatively little impact on crop grain yield or economic return.  To test this hypothesis, experiments were conducted in Michigan at three farms and one experiment station in 2007 and 2008.  With the exception of N management, the farms sites were managed primarily by the growers.  All sites were in a corn-soybean rotation where corn was the studied crop.  Six rates of urea fertilizer (0-225 kg N ha^-1) were broadcast and incorporated prior to planting into four replicate plots (RCBD) at each of the sites.  Field measurements included N₂O emission via static chambers, soil temperature, soil moisture, soil inorganic nitrogen (0-10 cm), and corn grain yield.  Measurements were taken immediately prior to fertilization, then on a 7-10 day frequency throughout the growing season.  Additional measurements were collected immediately following fertilization and rain events at the frequency of every 2-3 days.  Results from 2007 indicated that N₂O flux tended to increase with increasing N rate.  Further data analysis will indicate the impact that reductions of recommended N rates may have on N₂O flux.