Management of Nitrogen in Irrigated Canola for Agronomic Efficiency and Greenhouse Gas Reduction.

Canola is the most extensively grown crop under irrigation in the Canadian Prairie region.  Yields (and N recommendations) are high and increasing due to improved varieties and management practices.  Advances in fertilizer products and application options under irrigation, and concerns about greenhouse gas (GHG) emissions, have created a need to re-assess management of N for irrigated canola.

One field trial was conducted each year since 2012 to determine responses of irrigated canola to N rate (0-100-200kg N/ha), and placement/timing (broadcast/incorporated, side-banded, and split [50% top-dressed]), in terms of yield, quality and GHG emissions.

For 2012-2015, no significant yield responses to the treatments occurred in two of the years.  In one year hail reduced yields by about two-thirds.  In the other year soil residual N was high and yield was reduced by fall frost after late re-seeding of the trial.

Seed yields with optimum N in the two N-responsive years exceeded 3000 kg/ha; yields in the 0-N check treatment were reduced by about 50 and 30%.  Agronomic optimum N rates appeared to be somewhat lower than would usually be recommended for high-yield irrigated canola at the low soil nitrate levels that existed.  Yields did not differ significantly among the N placement/timing treatments.

Seasonal cumulative nitrous oxide emissions varied greatly between years (5+ times higher in the two years with wet early-season conditions).  Emissions were always lowest in the 0-N check treatment, and increased with applied N rate in the other treatments.  Effects of timing/placement also varied among years, with the sideband treatment showing higher emissions than the other treatments in two of the years; the split treatment always had among the lowest emissions.  Applying only the agronomic optimum N rate, and delaying application of a portion of it, may minimize GHG emissions based on results to-date.

The presentation will also include 2016 trial results.