Strategies for Optimizing Nitrogen Use In Corn with and without Subsurface Drainage.

Excessive soil moisture can impact planting date, plant establishment, and nitrogen availability, resulting in reduced yields and nitrogen use efficiency.  Heavy soil and frequent early rainfall can make early season field operations a challenge.  Nitrogen loss potential by means of leaching or denitrification is greater with heavy rainfall and highly saturated soils.  Nitrogen management practices such as urease and nitrification inhibitors, and split applications may be used to reduce nitrogen lost during the growing season; improving nitrogen use efficiency and crop productivity.  Improved crop production resulting from subsurface drainage is in large part due to better physical conditions for field operations, but could also be due to less nitrogen being lost due to denitrification, and a deeper unrestricted root zone area that allows for greater crop rooting.  The objective of this study was to see if nitrogen management practices could reduce nitrogen losses and improve crop productivity with and/or without subsurface drainage on heavy clay soil in eastern North Dakota.  Five field trials were conducted in 2009 and 2010 in eastern North Dakota.  Treatments consisted of a factorial combination of nitrogen management practices (urease, starter fertilizers, nitrification inhibitors, and split applications), nitrogen rates (56, 112, 168, 224 kg ha^-1), and the presence of subsurface drainage (two locations).  Due to a cool, dry growing season near Fargo, ND in 2009 there was no significant difference in yield among drainage treatments.  Differences in yield were seen with different nitrogen rates, as would be expected, but nitrogen management practices did not affect yield.  The interactions between nitrogen management practices and drainage were also not significantly different.  End of season stalk nitrate tests also showed differences in nitrogen use efficiency with different nitrogen rates, but not N management practices.  Data from 2010 will also be reviewed.