Tillage and N Source Effects On Nitrous Oxide Emissions From Soils.

A three-year study was conducted to determine the effectiveness of varying the application times and N fertilizer source on corn grain yields and N₂O losses from soil under conventional tillage (CT), zone tillage (ZT) or no-tillage (NT) in Southwestern Ontario.  On average, there was 2.80 kg N ha^-1 lost from the CT treatments and these losses were reduced by 10.7% with NT and by 36.4% with ZT.  Applying N as a sidedress application reduced N₂O losses by 37.9% compared to applying all of the fertilizer N as a pre-plant application.  In 2004, there were significant effects of urea source on N₂O emissions with regular urea having 1.8 to 4.2 times more N₂O evolved than coated urea when applied to CT treatments.  However, urea source did not significantly affect N₂O emissions in either 2005 or 2006.  The 3-yr corn grain yields were on average, 12% greater with CT (9.38 t ha^-1) than NT (8.35 t ha^-1). Although the yield was slightly lower with ZT (9.01 t ha^-1) compared to CT, the yield differences were not significant. The influence of tillage on crop yields and N₂O emissions most likely reflects the changes which occurred in soil physical (soil moisture, temperature) and biological properties (residue inputs and decomposition rates) resulting from the tillage operations.