Balancing agronomic and environmental outcomes using enhanced efficiency nitrogen fertilizers
Date: September 28, 2022
Term: 3 years, ending September 2022
Status: Complete
Researcher(s): Richard Farrell, Kate Congreves, Reynald Lemke, Trang Phan, University of Saskatchewan
SaskCanola Investment: $57,927
Total Project Cost: $208,994
Funding Partners: Saskatchewan Agriculture Development Fund, Saskatchewan Canola Development Commission
Grower Benefit(s)
Management options aimed at N2O emissions reductions should target enhanced synchronization of N supply with crop N demand.
In western Canada, the primary targets for emissions reductions should be the controls on emissions occurring at spring thaw.
Late season rains can trigger significant N2O emissions under conditions where crop N removal is limited.
Non-growing season N2O emissions contribute a disproportionately large fraction of total annual emissions.
Emissions of N2O occur even under drought conditions.
Project Summary
Producers are increasingly looking towards technologies that can protect their fertilizer investment while improving both their agronomic and environmental performance. Previous research has shown that substantial reductions in N2O emissions are achievable by combining enhanced efficiency N fertilizer (EENF) technologies with more advanced, 4R-based N management practices. The objective of this project was to quantify the influence of EENFs on crop nitrogen use efficiency, yield and N2O emissions in canola. Although the study results were severely impacted by significant moisture deficiencies in both years, the study provided new data on the performance of two common EENF products. Although, the results are not reflective of what producers might expect in a 'normal' year, the study results did provide strong evidence that the primary targets for emissions reductions in western Canada should be the controls on emissions occurring at spring thaw and enhanced synchronization of N supply with crop N demand.
With the cost of synthetic nitrogen fertilizer increasing and the emergence of lower cost enhanced efficiency N fertilizer (EENF) technologies, producers are increasingly looking towards technologies that can protect their fertilizer investment while improving both their agronomic and environmental performance. Previous research has shown that substantial reductions in N2O emissions are achievable by combining EENFs with more advanced, 4R-based N management practices; i.e. practices that involve applying N fertilizer using the Right source at the Right rate, Right time, and with the Right placement.
In this three-year study over two field seasons, the overall objective was to evaluate and compare the performance of two stabilized EENF products SuperU (urea treated with dual urease and nitrification inhibitors) and eNtrench (urea treated with a nitrification inhibitor) with that of conventional granular urea in both fall and spring applications. Researchers quantified and compared crop N uptake, NUE, canola yield and N2O emissions for all treatments. Yield-scaled N2O emission factors were also calculated for each fertilizer type and application timing to determine the combination that optimized the balance between agronomic and environmental outcomes.
Field trials were conducted at the University of Saskatchewan on plots that had been previously cropped to barley. The fertilizer treatments, including conventional granular urea (46-0-0), SuperU and eNtrench were applied in the fall or spring and at the soil test recommendation (STR) or at 70% of the STR. In addition to the fertilizer treatments, the study included a non-fertilized check plot that was used to quantify background emissions and calculate fertilizer-induced emissions. The EENF products and conventional granular urea were broadcast by hand in the late fall after soil temperatures had fallen below 7°C for five consecutive days, or at planting the following spring. The fertilizer was incorporated into the soil to a depth of about 10 cm immediately after surface application. The plots were seeded with hybrid canola in the spring, using standard agronomic practices.
The results of this study were significantly impacted by drought conditions in 2020 and 2021, with yields that were about 30 per cent and 90 per cent lower than target yields in 2020 and 2021, respectively. Overall, the study showed that under these conditions the EENFs had no effect on either yield or NUE. Generally, the fertilizer rate effects were not significant. The results of the daily N2O emissions showed that major emission events coincided with snowmelt/spring thaw (ST) and the spring seeding/fertilizer operations. For fall N application, the magnitude of emissions during the spring thaw was determined by environmental and soil conditions both during the overwinter period and at ST in the early spring. Cumulative ST emissions, which were much greater in 2020 than in 2021, were generally greater with fall applications than those associated with the spring N applications. This reflects the differences in both soil and environmental conditions and available N supply.
Although the study results were severely impacted by significant moisture deficiencies in both years, the study provided new data on the performance of two common EENF products. However, the results are not reflective of what producers might expect in a 'normal' year. Overall, the results provided strong evidence that the primary targets for emissions reductions in western Canada should be the controls on emissions occurring at spring thaw and enhanced synchronization of N supply with crop N demand. Future research should also target N management strategies that improve synchronization of N supply with crop N demand, which could include detailed N uptake studies performed under varying soil and environmental conditions.