Canola Response to Enhanced Efficiency Nitrogen Fertilizer Products and Blends – Year 2

Objectives

The overall project objective was to investigate and demonstrate Argentine canola (Brassica napus) response to side-banded enhanced efficiency fertilizer (EEF) nitrogen (N) products and blends, relative to untreated urea. The focus was primarily on canola establishment, yield, and seed quality; however, with this information, we also aimed to determine whether the agronomic N use-efficiency (ANUE) of side-banded urea could be improved with EEF formulations and provide information on which products performed best for a range of Saskatchewan environments.

Project Description

Exploring potential benefits of enhanced efficiency fertilizer (EEF) nitrogen (N) products and blends with side-banding was identified as a priority by SaskOilseeds. In the spring of 2025, field trials to address this topic were initiated at Indian Head, Melfort, Prince Albert, Scott, Swift Current, and Yorkton, Saskatchewan. These locations encompass a wide range of soil/climatic conditions. In addition to a control and several rates of side-banded urea, the treatments included polymer coated urea (ESN®), a urease inhibitor (ANVOL®), a nitrification inhibitor (eNtrench®), and a dual urease/nitrification inhibitor (SUPERU®). In addition to being applied alone, ESN® and SUPER® were tested in 25%, 50%, and 75% blends with untreated urea. Evidence of stand reduction with high rates of untreated urea was occasionally detected. At Scott in 2024, polymer coated ESN® reduced this risk with clear improvements in establishment as the proportion of ESN® in the blend was increased; however, no other EEF products showed such benefits. At 5/12 sites, high residual N or other limiting factors resulted in essentially no benefit to N fertilization; however, the remaining sites were responsive. For all sites, the risks of environmental N losses (denitrification, leaching, and volatilization) were generally considered low, and we did not observe any yield benefits to any of the EEF N products evaluated. The seed oil and protein measurements did not provide any evidence of improved NUE relative to untreated urea with EEF N products. The agronomic N use-efficiency (ANUE) estimates were effective for describing the overall economic response to N fertilizer applications and the diminishing yield responses at increasingly high rates but were generally too variable to detect or describe differences amongst N formulations. While yield benefits to EEF products are more likely with less optimal application timing/placement, they could occur with side-banding in years, locations, or landscape positions where environmental N losses are higher.

Grower Benefits

With high residual soil nitrogen (N) or other environmental issues diminishing our responses to N fertilizer at multiple sites (i.e. SC-25, SW-24, SW-25, YK-24, and YK-25), this project has proven more challenging than expected. While PA-24 and PA-25 had to increase the target N rates to accommodate high background N and data from PA-25 was quite variable, these sites were still responsive to N fertilization. However, this revision creates challenges for combined data analyses and presentation of results.

In a few cases, we saw evidence of seedling toxicity with high rates of side-banded N. While the losses were not generally large enough to negatively impact yields, polymer coated urea (ESN®) reduced these negative impacts at SC-24 and, to a lesser extent, SW-24. Polymer coated ESN® is known to improve seed safety and is commonly recommended to allow higher N rates to be applied with single shoot drills; therefore, this result was not unexpected. Side-banding is generally considered safe for high rates of urea; however, minor NH4 toxicity in sensitive crops often still occurs under dry conditions or if separation between the seed and fertilizer is compromised. Injury associated with side-banded urea is typically minor and outweighed by the benefits of enhanced fertility, but such risks are still important to acknowledge and manage to the best of our ability. 

Under the conditions encountered to date, there have been no cases where enhanced efficiency fertilizer (EEF) N products improved yields over untreated urea. Significant effects on seed quality were exceedingly rare and, as such, difficult to predict. The lack of response was attributed to the risk of environmental N losses being low with side-band placement and under the conditions encountered. Although denitrification losses can be sizeable in saturated soils, this process only affects N that has already converted to nitrate. Concentrating N in bands beneath the soil surface slows and delays nitrification, even without the use of inhibitors (i.e., eNtrench® or SUPERU®) or polymer coatings (i.e. ESN®). Despite high precipitation in May and June at many sites in 2024, initial soil moisture was extremely low. As such, the plots were unlikely to be saturated for long if they were situated on reasonably well drained land. Aside from lower slope or depressional areas on coarse textured soils, leaching losses during the growing season, which polymer coatings or nitrification inhibitors can reduce, are rather unlikely. Furthermore, the risk of N loss due to NH3 volatilization was also low with the early season precipitation in 2024. Simply placing the N beneath the soil surface is enough to greatly reduce or eliminate volatilization, regardless of whether a urease inhibitor is used. While volatilization losses are possible with shallow banding at high rates in coarse soils, or if the furrow/fertilizer band is not properly sealed, timely rain can largely eliminate this risk. In 2025, several sites were extremely dry in May, but conditions improved in June and the soils were never likely saturated long enough to pose a serious risk of denitrification or leaching losses. While these initially dry conditions might increase risk of volatilization with shallow banding, the worst affected sites also had more acidic soils (pH < 6, which increases the NH4:NH3 ratio) and either had relatively fine-textured soils (i.e., ME-25) or were generally not responsive to N. With these environmental conditions in mind, the lack of advantages of EEF N formulations over urea, was not unexpected. Again, EEF N formulations will only be advantageous when the crop is responsive to N fertilization, and the risk of environmental N loss is sufficient.

The agronomic N use-efficiency (ANUE) measurements were good indicators of the overall economic response to N fertilizer and diminishing returns with increasingly high N rates but have generally been too variable to be useful for detecting differences between forms. It is also important not to misinterpret these values. As indicated earlier, ANUE is not an absolute measure of NUE. For example, an ANUE value of 30% does not mean that 70% of the N was lost to the environment. A substantial portion of this applied N could remain in the crop material (straw, chaff, roots), be immobilized, and/or remain in the soil as mineral N forms. The ANUE values in the current project only account for the estimated proportion of the applied N, as urea or EEF N (i.e., not the N from monoammonium or ammonium sulfate), that was physically removed in the harvested grain.

While we expect EEF N products to be more beneficial with less desirable timing and placement options (i.e., fall applications, surface broadcast applications), such products can still be beneficial and economically advantageous with side or mid-row banding under certain conditions. However, our results reinforce that such benefits are never guaranteed and, when timing, placement, and environmental conditions are all favorable, can be unlikely. The risk of environmental losses with in-soil banded N will vary with year, regionally, and with landscape position (i.e., greater potential for denitrification in depressional areas). Importantly, small plot trials are not typically placed in the depressional areas of fields where some of these losses will be most severe on a more localized basis. Furthermore, nitrification inhibitors consistently reduce N2O emissions, which can occur both with rapid nitrification and denitrification processes. Nitrous oxide emissions are generally too small to impact yields or economic returns but are important environmentally. Depending on commodity and fertilizer prices, relatively small yield benefits can often cover the cost of EEF N products. Government programming is sometimes available to reduce the cost of these technologies which, if utilized, can greatly improve the economics of qualifying EEF N formulations.