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Agronomy Update
Agronomy update: EEF liquid N strategies for winter wheat

September 8, 2023  By Bruce Barker


With the development of enhanced efficiency fertilizers (EEF), winter wheat growers have the opportunity to improve nitrogen use efficiency (NUE) and reduce greenhouse gas emissions with liquid nitrogen (N) fertilizers. Research was conducted to see how N source influences grain yield, protein content and other agronomic performance under dryland and irrigated conditions, and to determine if N sources and placement impact greenhouse gas emissions.

Research scientist Brian Beres with Agriculture and Agri-Food Canada led five years of trials from 2013 through 2018. Irrigated sites were at Agriculture and Agri-Food Canada and Farming Smarter, Lethbridge, Alta. Dryland sites included Lethbridge, Falher, Edmonton, and St. Albert, Alta., and Brandon, Man.

AC Flourish, a Canada western red winter milling quality variety, was grown at each site with regular agronomic practices.

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Soil testing was completed prior to seeding. Nitrogen fertilizer application rates were based on 80 per cent of the recommended soil test rates. These rates ranged from 65 pounds N per acre to 175 lbs n/ac (73 kg N/ha to 196 kg N/ha) for the irrigated sites, and 55 to 162 lbs N/ac (62 kg N/ha to 182 kg N/ha) for rain-fed sites.

Six different N sources were tested, and the study included a 0N control:

  1. untreated granular urea (46-0-0 ), 
  2. untreated liquid urea ammonium nitrate (UAN; 28-0-0), 
  3. urease inhibitor N-(n-butyl) thiophosphoric triamide (NBPT) treated UAN (Agrotain Ultra), 
  4. nitrification inhibitor dicyandiamide (DCD) treated UAN (Nitrapyrin; eNtrench), 
  5. urease inhibitor + nitrification inhibitor dicyandiamide (DCD) treated UAN (NBPT+DCD; (Agrotain Plus), and, 
  6. Polymer Coated Urea (PCU; Environmentally Smart N, ESN). 

UAN placement used a split-applied approach with 50 per cent of N side- or midrow-banded at seeding and 50 per cent applied in-crop in early-spring (Feekes 4). The exceptions were PCU all side-banded at planting, and full rate of untreated urea broadcast early-spring. Broadcast liquid N used SJ3 Teejet liquid or John Deere stream nozzles.

Nitrous oxide (N2O) and methane (CH4) emissions were measured at the ‘Lethbridge Dry’ site from 2014 to 2017. These measurements took place from seeding in September to harvest in July for each treatment, and were expressed as net CO2-equivalent emissions (CO2-eq).

Under irrigated conditions, UAN treated with a urease inhibitor (Agrotain Ultra) had the highest yield at 76 bu/ac (5.12 tonne/kg), but was statistically similar to untreated UAN at 75 bu/ac (5.06 t/ha) and the urease + nitrification inhibitor (Agrotain Plus) at 74 bu/ac (4.96 t/ha). Agrotain Ultra treated UAN was statistically higher than untreated urea by 6.4 per cent, than the nitrification inhibitor (eNtrench) by eight per cent and PCU (ESN) by 14 per cent.   

Protein content under irrigated conditions were similar among all treatments ranging from 10.7 for untreated urea to 11.1 for the urease + nitrification inhibitor Agrotain Plus. Industry accepted standard is 11 per cent grain protein content or higher.

Dryland yields were similar across many treatments with untreated UAN, untreated urea, urease inhibitor-treated UAN and dual treated urease-plus nitrification inhibitor statistically similar at around 65 bu/ac (4.36 t/ha). Statistically, the lowest yielding were the nitrification inhibitor-treated UAN at 63 bu/ac (4.25 t/ha), and PCU at 63.8 bu/ac (4.28 t/ha) – which, agronomically, are very similar to the highest yielding treatments.

Protein content was lowest in the nitrification-inhibitor UAN (11.2 per cent) and urease plus nitrification (11.4 per cent) treatments. The other treatments were similar at 11.4 per cent to 11.6 per cent.

The researchers suggest that the combined results from irrigated and rain-fed sites in this study show that urease inhibitor-treated UAN has more potential to enhance winter wheat grain yield and agronomic performance than treating UAN with a nitrification inhibitor. This was attributed to the urease inhibitor slowing urea hydrolysis and resulting NH3 volatilization loss. Stability analysis also found that a split-application of liquid UAN with an urease inhibitor not only improves grain yield and optimizes protein content, but also provides improved yield stability compared to the other treatments.

The short story on greenhouse gas emissions is they were unaffected by N source at the three dryland site-years, and EEF-treated UAN was similar to untreated UAN or untreated broadcast urea.

The researchers felt that the growth habit of winter wheat made it less responsive to EEFs effects on greenhouse gas emissions, and the 80 per cent N application rate may also have helped reduce emissions.

Overall, the results show that using liquid UAN treated with an urease inhibitor in a 50-50 split application provides adequate protein and high, stable winter wheat yield. Greenhouse gas emissions were not reduced in this study with the application of EEF treatments. 


Bruce Barker divides his time between CanadianAgronomist.ca and as Western Field Editor for Top Crop Manager. CanadianAgronomist.ca translates research into agronomic knowledge that agronomists and farmers can use to grow better crops. Read the full Research Insight at CanadianAgronomist.ca.

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