Enhanced efficiency nitrogen fertilizer: what does the newest prairie research say?

This article is adapted from Fast et al. (2023) Integrating enhanced efficiency fertilizers and nitrogen rates to improve Canada Western Red Spring wheat.

Nitrogen (N) loss and Enhanced Efficiency Fertilizers (EEFs) are becoming increasingly popular topics among farmers and agronomists. EEFs are products with different mechanisms that seek to prevent N loss. There are multiple products available to farmers that are available for purchase. This brings the questions: do the EEFs bring benefits to my farm? Which product is the best option for my farm? And what is the best practice for the EEFs?

New research conducted in Alberta and Saskatchewan, between 2019 and 2022, comes to aid in the decision-making. The research asks the questions of:

1) Does an EEF provide benefits to yield compared to urea?

2) What is the N requirement of a modern high-yielding CWRS variety to optimize both grain yield and protein?

How was the trial conducted?

Variety used in the research:

AAC Viewfield seeded at 400 seeds/m² (37 seeds/ft²)

N Treatments:

Each N source is tested with the four N rates. All N fertillizers were applied at planting, mid or side-row banded.

Note: the ESN treatment is a 75:25 blend of ESN : urea

Trial Locations:

Dark brown soil zone: Scott, SK; Lethbridge, AB.

Black and Dark Grey soil zones: Indian Head, SK; Vermillion, Edmonton, Barrhead and Beaverlodge, AB.

What did they find?

Are there yield benefits to using EEFs?

In Dark Brown soil zone, using an EEF resulted in equal or higher yield compared to urea. The dual inhibitor (SuperU) achieved a higher yield of 74.5 bu/ac, while other EEFs and urea had similar yields, ranging from 71.7 to 73.8 bu/ac.

Polymer-coated urea (ESN) had the lowest yield compared to all EEFs. This is likely due to ESN release being more impacted by soil moisture and temperature. A lack of either can overly slow N release, consequently impeding nitrogen availability during the early stages.

The benefit of ESN is seed safety. When applying seed-placed nitrogen or if adequate seed-fertilizer separation cannot be achieved, ESN provides a safe option to apply all or close to all N fertilizer requirements at planting (~100lbs N/ac) without causing toxicity effects to seeds leading to seed desiccation.

In Black and Grey soil zones, all the EEFs had similar yields to urea, ranging from 77.5 to 78.5 bu/ac. Black and Dark Grey soil generally has increased mineralization rates due to higher soil organic matter and, in some cases, residual soil nitrogen. This is likely the reason that different N sources provided similar yields in Black and Dark Grey soil.

Overall, in all soil types, EEF use resulted in similar or slightly higher yield compared to urea alone.

Note: the differences in response between Dark Brown and Black/Grey soil zones are not clear cut. Soil moisture is the driver behind the N cycle. Under drought conditions, Black/Grey soil might release less N through mineralization and behave differently.

How about grain protein?

In all soil types tested in this study, the EEFs had similar grain proteins to urea. In Dark Brown soil, grain protein ranged from 14.1% to 14.3% for all EEFs; in Black/Grey soils, it averaged around 13.8%. Notably, all N sources produced grains that met the CWRS protein requirement of 13.5%.

Are there economic benefits from using EEFs?

Despite typically being priced higher than urea, EEFs had comparable or higher net returns (see the figure below). Please note that the net returns calculated in this study only consider revenue (grain yield x grain price) and N cost (N rate x N price). Other fixed costs are not included.

Net return = (yield x grain price) - (N rate x N price)

More specifically, in Dark Brown soil zone, the dual inhibitor (SuperU) provided a higher net return ($62/ha or $25/ac) than urea. The other EEFs, namely Agrotain, eNtrench and ESN, achieved net returns similar to that of urea.

In Black/Grey soils, all the N sources had comparable net returns statistically.

Please note that fertilizer costs are based on quotes from December 2022. Grain price was based on CWRS price at the time. The net returns are subject to change when N and grain prices fluctuate.

Growers are encouraged to do their own calculations and/or on-farm trials to make farm-specific economic calculations.

Figure: Net return response to EEFs and urea. Note: the net returns in this table only consider revenue (yield x grain price) and fertilizer cost. Other fixed costs were not included.

Source: A., Strydhorst, S., Wang, Z., Hernandez-Ramirez, G., Hao, X., Semach, G., Thompson, L., Holzapfel, C., Enns, J., Spaner, D. and Beres, B.L. (2023). Integrating enhanced efficiency fertilizers and nitrogen rates to improve Canada Western Red Spring wheat. Canadian Journal of Plant Science.

Do EEFs provide better nitrogen use efficiency?

In Dark Brown soil, the dual inhibitor (SuperU) had the highest plant N uptake. In other words, when N rate was the same, plants were able to use the highest amount of N from SuperU. This makes the dual inhibitor the most agronomically efficient. It produces 14.3 kg of grain yield per kg of N applied, compared to 12.6 kg/kg N from urea. Other sources of EEFs, including Agrotain, eNtrench and ESN had similar nitrogen use efficiencies to urea.

In Black/Grey soil zones, all nitrogen sources had comparable nitrogen use efficiency. Overall, EEFs provide at least equal, and potentially higher N use efficiency.

How did N rate impact yield and protein?

Grain yield trended upward linearly as N rate increased, up to 120 kg N/ha (107 lbs N/ac). Compared to 60 kg N/ha (54 lbs N/ac), the higher rate of 120 kg N/ha (107 lbs N/ac) increased yield by 6.4 bu/ac (or 9%) in Dark Brown soil, and 8 bu/ac (11%) in Black/Grey soils.

Increasing N rate from 120 to 240 kg N/ha (107 to 214 lbs N/ac) only provided small yield increases. Grain yield exhibited the law of diminishing returns in this N rate range.

Grain protein increased linearly when N rate increase. For example, in Dark Brown soil, when the N rates were 60, 120 and 180 kg N/ha (54, 107 and 161 lbs N/ac), grain protein increased from 12.4% to 14.0% and 15.0%, respectively. The highest rate of 240 kg N/ha (214 lbs N/ac) did not bring additional grain protein. It means that growers can pursue higher protein premiums with higher N rates, but only if it is economically beneficial.

Take home message

• Compared to urea, EEFs provide equal and potentially higher yield and nitrogen use efficiency. In other words, EEFs provide an “insurance” for more stable and potentially higher grain yield.

• EEFs did not impact grain protein, regardless of soil type.

• Despite being priced slightly higher than urea, EEFs showed comparable or improved net returns.

• The highest net returns are achieved using N rate of 120 kg N/ha (107 lbs N/ac), banded at seeding time. Higher N rates can be used to obtain protein premiums, but it is suggested to compare the additional cost of N with the protein premium and only implement when beneficial.

• The use of an EEF in conjunction with proper N rates helps optimize modern CWRS production.

Next step questions

• Do varieties respond differently to EEFs?

• How do timing and placement impact nitrogen use efficiency (NUE) of the EEFs?

• How to use Genetic x Environment x Management approach to optimize CWRS production?

Dr. Brian Beres’ team conducted research to answer these questions. Stay tuned for the next article!