Grenfell trial shows IPF EEFs reduce nitrogen losses
Author: Dr Robert Impraim – Research & Development Agronomist
As you plan topdressing strategies for your winter crops, now is the time to consider how you can retain more nitrogen (N) in your system and reduce losses to the environment.
New field trial results from Incitec Pivot Fertilisers (IPF) confirm that enhanced efficiency fertilisers (EEFs), specifically Green Urea NV® and eNpower®, significantly reduce emissions of nitrous oxide (N₂O) and ammonia (NH₃), the two major N loss pathways from urea-based fertilisers.
This research forms part of a long-term N by phosphorus trial established in 2007 at ‘Glenelg’ near Grenfell, Central West NSW. In 2024, this site was used to evaluate the emission reduction potential of IPF’s patented inhibitor technologies under real farming conditions.
This work forms part of a broader research initiative evaluating the effectiveness of IPF’s patented inhibitor technologies, smart fertilisers, more broadly known as EEFs, in reducing fertiliser-related emissions on-farm. It reflects our ongoing commitment to helping growers optimise N use and improve productivity through smarter fertiliser management.
The trials demonstrated that using eNpower and Green Urea NV significantly reduced N₂O emissions by 64–73% compared to untreated urea, depending on the rate of N applied.
The study also evaluated Green Urea NV’s performance in reducing NH₃ volatilisation, an indirect greenhouse gas (GHG) loss pathway. Results showed NH₃ losses were reduced by 48–83% over a 16-day period, varying by N application rate.
While untreated urea lost between 20–25% of applied N as NH3, Green Urea NV consistently mitigated these losses. Although its effectiveness declined over time, it remained substantially more effective than untreated urea throughout the trial period.
Figure 1: Grenfell trial site, wheat plots with nitrous oxide and ammonia sampling chambers.
Source: Robert Impraim, 2024
How was the trial conducted?
Ammonia trial
Ammonia emissions were measured over a 16-day period following surface application (topdress) of Urea and Green Urea NV at five N rates: 0, 15, 30, 45, and 60 kg N/ha. To maintain consistent total N inputs, similar rates of urea or eNpower-coated urea were also applied at sowing. This brought the total N rates across the trial to 0, 30, 60, 90, and 120 kg N/ha.
NH3 measurement
Ammonia was captured using acid-treated foam placed in a 150 x 300 mm (diameter x height) PVC pipe inserted into the soil to about 5 cm deep to trap emitted NH3 from the soil (Figure 2). The foams were replaced every four days, with the trapped NH₃ (as NH₄⁺) extracted and analysed via flow injection analysis. The total volatilised NH₃ was calculated based on sampling area, duration, extract concentration and volume.
Nitrous oxide trial
Nitrous oxide emissions were measured over 120 days at three N application rates: 0, 60, and 120 kg N/ha. eNpower-coated urea was banded at sowing, and Green Urea NV was surface-applied as a topdress. Total N rate applied: 0, 30, 60, 90 and 120 kg N/ha. Each of these plots (except the 0 kg N/ha) received 20 kg P/ha to reflect common agronomic practice.
N2O measurement
Nitrous oxide measurement was only done on the 0, 60 and 120 kg N/ha plots. N₂O was measured using static PVC chambers consisting of a fixed base and a removable top (Figure 3). At each sampling event, gas from the chamber headspace was collected into pre-evacuated vials at half-hour intervals over one hour and analysed via gas chromatography. Emissions were calculated using chamber dimensions, sampling intervals, and N₂O concentrations.
Figure 2: NH3 measuring chambers placed in the field
Source: Robert Impraim, 2024
Figure 3: N2O measuring chamber (blue) placed in the field
Source: Robert Impraim, 2024
Table 1: Soil properties at the trial site (tested at Nutrient Advantage Laboratory).
| Analyte | Results |
| Texture | Clay loam |
| pH(H2O) | 6.7 |
| pH(CaCl2) | 6.2 |
| Total N | 0.1% |
| Total C | 0.8% |
| NO3–-N | 53 mg/kg |
| NH4+-N | 5.9 mg/kg |
| P (Colwell) | 51 mg/kg |
| CEC | 5.1 cmol(+)/kg |
Source: Robert Impraim, 2024.
Reduction in N₂O loss
At an application rate of 60 kg N/ha, split evenly between eNpower-treated urea at sowing and Green Urea NV at topdressing, N₂O emissions were reduced by 63.7% compared to using untreated urea alone. This reduction accounts for background emissions observed in control plots with no N applied. At the higher rate of 120 kg N/ha, the combined use of eNpower and Green Urea NV achieved an even greater reduction of 72.3% in N₂O emissions. Across all treatments, the N₂O emission factor (the proportion of applied N emitted as N₂O-N) ranged between 0.2% and 0.3%.
Figure 4: Total N2O emission from soil over 120 days following fertiliser application. Fertiliser (as Urea or eNpower + Green Urea) rate 0-120 kg N /ha. Bars represent standard error of means (n = 4).
Source: Robert Impraim, 2024
Reduction in NH3 loss
Out of the 15–60 kg N/ha applied as urea, between 4 and 16 kg N/ha was lost through NH₃ volatilisation. Green Urea NV significantly reduced these losses, cutting NH₃ emissions by 48–83% over the 16-day monitoring period. Although its effectiveness declined slightly towards the end of the sampling period, Green Urea NV consistently minimised NH₃ loss relative to untreated urea.
With untreated urea, 89–95% of total NH₃ emissions occurred within the first eight days after application. In contrast, Green Urea NV slowed urea hydrolysis, except at the 30 kg N/ha rate (where 70% of emissions occurred within eight days), only 23–47% of total NH₃ loss occurred in the same period. This demonstrates Green Urea NV’s ability not only to reduce overall NH₃ loss but also to extend N availability, supporting more efficient nutrient uptake by crops.
Figure 5: Total NH3 emission from soil over 16 days following fertiliser application. Fertiliser (as Urea or Green Urea) rate 0-60 kg N/ha. Bars represent standard error of means (n = 4).
Source: Robert Impraim, 2024
Why reducing N₂O and NH3 emissions matter
Nitrous oxide has 273 times the global warming potential of carbon dioxide, and is one of the three key GHGs, along with carbon dioxide and methane (CSIRO & Bureau of Meteorology, 2024), contributing to human-driven climate change. N₂O can remain in the atmosphere for more than 100 years and it is also an ozone-depleting substance (Ravishankara et al., 2009).
While Australian grain production accounts for less than 2% of Australia’s total emissions, reducing GHG emissions through improved fertiliser use efficiency is important.
It will achieve positive environmental outcomes, contribute to Australia’s emissions reduction target of 43% and net zero emissions by 2050, and potentially help protect market access. In the three years to 2023–24, Australia exported around 78% of our wheat.
Ammonia emitted to the atmosphere reduces air quality and negatively impact human health. When deposited, NH3 can lead to soil acidification and decline in water quality (Chaopu Ti et al., 2019). From an economic perspective, NH3 volatilisation leads to significant loss of N from the cropping system and lost grain yield potential.
The trial has demonstrated the importance of IPF’s eNpower and Green Urea NV in mitigating the emissions of N2O and NH3 in cropping systems.
Looking ahead, IPF will be conducting more trials this year measuring emissions from N application in winter crops at multiple locations including Bacchus Marsh, Victoria.
Summary
eNpower and Green Urea NV reduced nitrous oxide emissions by 64–73% compared to untreated urea, depending on the N application rate. Overall, 0.2–0.3% of the applied N was lost as nitrous oxide.
Green Urea NV also significantly reduced ammonia volatilisation by 48–83% over the 16-day monitoring period, again depending on the N application rate, compared to untreated urea.
What this means for you
The data highlights a strong opportunity to reduce N losses and improve fertiliser efficiency. eNpower and Green Urea NV reduced nitrous oxide emissions by up to 73%, and Green Urea NV also significantly cut ammonia losses by up to 83% over the trial period. These results suggest that smart fertilisers, IPF’s enhanced efficiency fertilisers (EEFs), can play a key role in improving N use while supporting environmental compliance.
If you’re looking to get more from your N investment and reduce losses in high-risk conditions, now’s the time to consider how these options could fit into your system. Speak with your local agronomist to assess where and how these products could deliver value on your farm.
Further information
For more information, feel free to contact Dr Robert Impraim, Research & Development Agronomist at robert.impraim@incitecpivot.com.au.
Acknowledgement
Firstly, we would like to thank our trial site co-operators for their generosity over many years – Duncan Lander 2007-2015, and David Partridge 2016-2021.
Thank you also to:
- Clint Sheather, Jim Laycock for their work managing the ‘Glenelg’ long term trial.
- Kaylx for managing the site
- Clint Sheather, Elle Scannell, Jim Laycock, Fiona McDonald, Bilal Gill and Bede O’Mara for collection of the samples.
References
A. R. Ravishankara, John S. Daniel, & Robert W. Portmann. (2009). Nitrous Oxide (N2O): The Dominant Ozone-Depleting Substance Emitted in the 21st Century. Science, 326, 123–125.
Chaopu Ti, Longlong Xia, Scott X. Chang, & Xiaoyuan Yan. (2019). Potential for mitigating global agricultural ammonia emission: A meta-analysis. Environmental Pollution, 245, 141–148.
CSIRO, & Bureau of Meteorology. (n.d.). State of The Climate 2024. Retrieved April 16, 2025, from https://www.csiro.au/en/research/environmental-impacts/climate-change/State-of-the-Climate/Greenhouse-gases.
