Nitrogen stabilizers to enhance nitrogen use efficiency and reduce greenhouse gas emissions

Canadian annual use of N fertilizer is 1.8 M t, however due to natural soil and plant interactions with applied N fertilizers, efficiency of plant uptake and utilization, is often around 50% of applied N, in the year of application. Much of the applied N that is not taken up by the crop remains in the soil. However, there are some losses of applied N that can result in lower yields and grain quality, and are an environmental concern if N is leached into surface or ground water, or lost to the atmosphere as ammonia or nitrous oxide. Nitrogen stabilizers, including nitrification inhibitors (NI) and urease inhibitors (UI), and polymer coated – controlled release urea, may decrease greenhouse gas (GHG) emissions and increase N use efficiency (NUE).

In 2014, trials were conducted in spring at Lethbridge, and fall and spring at Edmonton and Devon, and with three N sources (eNtrench^(R) treated urea, ESN^(R) – polymer coated controlled release urea, SuperU^(R) and urea), with five N rates (0, 50, 75, 100 and 125% of soil test recommendations). Spring wheat was the crop grown at all sites. In this year, the data gathered included GHG emission using a steady state Photoacoustic gas monitor at the Edmonton site only. Soils samples were collected prior to application, two and four weeks after emergence, and post harvest to assess the nitrogen balance. NDVI was quantified at stem elongation and mid-anthesis, crop vigor ratings were taken. In addition to wheat yield, wheat stubble and grain nitrogen analysis, test weights and grain quality, were measured.

During the 2014 crop year, September 2013 through to September 2014, the weather was slightly cooler and drier compared to 30-year average weather. For example at the Devon, AB site the average temperature was 0.3 C compared to the 1.9 C of the 30-year average, and for precipitation 353.8 mm of moisture compared to the 30-year average of 404.9 mm. All enhanced N fertilizer forms, whether fall or spring applied, resulted in greater levels of ammonium N (NH₄⁺), and lower levels of nitrate N (NO₃^-) at two and four weeks after crop emergence, compared to using regular urea. Relative to urea, eNtrench had a N₂O emission reduction of 18% in the fall, but SuperU and ESN emissions were not reduced. In the spring eNtrench reduced N₂O emission by 24%, and SuperU by 30% compared to urea. ESN N₂O emissions were not reduced compared to urea. Another year of field experiments and data measurements will be collected during the 2015 growing season.