Author: Courtney Bills, IPF Technical Agronomist – QLD/NT 

As rolling summer storms build across the region, it’s a familiar sight to see tractors towing fertiliser spreaders across paddocks, racing to beat the first drops of rain. With ongoing labour shortages placing pressure on the agricultural industry, the ability to spread large areas quickly has become a major advantage for many growers. 

Surface application of fertiliser in the summer months is now common practice across numerous growing regions, and it’s often assumed that spreading on the surface results in only minimal nitrogen (N) loss. However, maximising N retention, improving fertiliser use efficiency and ultimately boosting crop profitability remain essential goals for every farming business. 

To help quantify these impacts, Incitec Pivot Fertilisers’ (IPF) Queensland team conducted a comprehensive trial program assessing volatilisation losses from both standard urea and Green Urea NV® – across fallow conditions and skip-row dryland cotton. The results clearly highlight the significant benefits of adopting Green Urea NV. 

Figure 1: Photo taken of the “Colonsay” trial site: In dryland cotton showing ammonia chambers. Image credit: Jan Edwards, Incitec Pivot Fertilisers. 

Understanding nitrogen losses when spreading fertiliser 

Published Australian research shows volatilisation losses can range from 0–34% of applied N 1 when fertiliser remains on the soil surface. Volatilisation is the loss of N as ammonia gas (NH₃), which occurs when urea is left exposed for long periods before being incorporated by rainfall or irrigation. 

Standard urea converts rapidly to ammonia gas under these conditions, with losses increasing significantly if rainfall does not occur within 36–48 hours of application2 

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[1] Barton L, Hoyle FC, Grace PR, Schwenke GD, Scanlan CA, Armstrong RD, Bell MJ (2022) Chapter One – Soil nitrogen supply and N fertilizer losses from Australian dryland grain cropping systems. In ‘Advances in Agronomy. Vol. 174.’ Ed. DL Sparks) pp. 1-52. (Academic Press)

[2] Schwenke G (2021) “Nitrogen loss pathways. How much is lost when urea is not mechanically incorporated after application?”. GRDC, Canberra. https://bityl.co/F1KY

A range of soil and environmental factors increase volatilisation risk,3 including: 

  • High soil pH (alkaline soils) 
  • Low cation exchange capacity (CEC) 
  • High organic matter or heavy stubble loads 
  • High temperatures and windy conditions 
  • Delayed or light rainfall after application 
  • Wet soil profiles that dry after fertiliser application 
  • Open canopies or bare soils. 

How Green Urea NV helps 

Green Urea NV contains 46% N and is coated with the patented urease inhibitor Lockdown NBPT (N-(n-Butyl)-thiophosphoric triamide + a comprehensive solvent package) which suppresses urease activity for up to 14 days. This slows the breakdown of urea, extending the window for rainfall or incorporation and helping protect more N for crop uptake. 

Figure 2: Activity of EEFs on the nitrogen cycle. Source: Incitec Pivot Fertilisers. 

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[3] Schwenke GD, Manning W, Haigh BM. (2014) Ammonia volatilisation from nitrogen fertilisers surface-applied to bare fallows, wheat crops and perennial-grass-based pastures on Vertosols. Soil Research 52, 805–821. https://doi.org/10.1071/SR14107

Trial overview 

Trials were conducted during the 2024/25 summer season at IPF’s long-term nitrogen/phosphorus site at “Colonsay”, Norwin, on Queensland’s Darling Downs. This site has supported continuous research since 1985 following 44 years of prior cropping. 

Figure 3: IPF’s long-term trial site at “Colonsay”, Queensland. 

Replicated plots received a single application of urea or Green Urea NV at rates of 0, 23, 46 and 92 kg N/ha. The application was made in February 2025 to both fallow and dryland cotton during mid flowering. 

Ammonia volatilisation was measured using closed PVC chambers, with samples collected at 4, 8, 12, 17 and 21 days after application. 

Results 

The trial included many conditions that favour high volatilisation during summer months: 

  • High soil moisture in fallow plots 
  • Strong winds throughout February 
  • High daytime and night-time temperatures 
  • Alkaline black self-mulching clay (average pH 8.5) 
  • No rainfall until 10–13 days post-application  
  • No mechanical incorporation 

Figure 4: Cumulative relative ammonia losses at “Colonsay” trial results across fallow and dryland cotton. White bars illustrate the standard urea results and downward arrows showing the reduction in relative nitrogen losses across all treatments in fallow and dryland cotton plots. Green coloured bars showing the Green Urea NV relative nitrogen losses (kg N/ha) considered to be low and significant when compared with the standard urea. Source: Jan Edwards, Incitec Pivot Fertilisers, 2025 

Ammonia losses began rapidly within four days of application and continued to increase through the 21-day monitoring period.  Once rainfall occurred on day 10, losses from standard urea increased sharply as hydrolysis accelerated. Although it is important to note that this trial adopted the use of closed chambers that sit over a section of the soil surface. Therefore, actual received rainfall does not hit the treated soil surface trial plot, though subbing moisture across the section drives losses to occur with the headspace gas (NH3) captured by the acid-treated sponge material. This sponge material is extracted and analysed with a flow analyser. Results from this analysis showed:

  • In dryland cotton, the highest urea loss occurred at the 92 kg N/ha rate: 11.2kg kg N/ha lost (~12%) 
  • Green Urea NV® losses at the same rate and site were significantly lower: 2.6kg N/ha (~2%) 

Across all treatments and both fallow and cotton, Green Urea NV consistently reduced volatilisation losses. The results demonstrate that even when fertiliser is applied well ahead of expected rainfall, Green Urea NV markedly improves N retention and uptake efficiency. 

Economics of using Green Urea NV

When economic returns were assessed at “Colonsay”, the benefits of using Green Urea NV were clear: 

Fallow: 

  • Standard Urea lost production value (cost of N loss): $36/ha   
  • Green Urea NV® benefit: $37/ha 

Cotton:

  • Standard Urea lost production value (cost of N loss): $62/ha 
  • Green Urea NV® benefit: $61/ha 
  • Equivalent to a 12% return on investment 

These figures demonstrate that even when accounting for the additional cost of the inhibitor, the improved N efficiency provides a strong economic advantage as shown below. 

Table1: Return of investment from “Colonsay” trial results (fallow and dryland cotton).  

Green Urea NVFallow Cotton 
Rate of nitrogen (kg/ha) 46 46 
Urea cost per tonne $800 $800 
N cost per kg $1.74 $1.74 
Cost of upgrading to Green Urea ($/t) $50 $50 
Increase in N cost per kg $0.11 $0.11 
Nitrogen saved (kg N/ha) 4.8 3.7 
Value of saved nitrogen ($/ha) $8 $6 
Additional production (kg/ha yield or kg/ha lint) 77 21 
Value of additonal production ($/ha) $29 $55 
Benefit ($/ha) $37 $61 
Investment in inhibitor ($/ha) $5.00 $5.00 
Return on investment 7% 12% 

Source: Jan Edwards, Incitec Pivot Fertilisers, 2025 

Key benefits of Green Urea NV

Green Urea NV supports summer spreading operations by: 

  • Tailored for spreading operations, improving farm efficiency 
  • Suited for all soil types and environmental conditions 
  • Summer broadcast proven for fallow and in crop applications 
  • Reducing N volatilisation risks and therefore keeping N in your soil 
  • Offering long-term storage stability (6+ months) 
  • Providing excellent handling with reduced clumping 
  • Using greener, safer solvents that support environmental stewardship 
  • Delivering rapid returns from a relatively small investment 
  • Being fully Australian-made and thoroughly field tested. 

Green Urea NV value calculator 

The Green Urea NV Value Calculator is an online tool that helps growers estimate potential savings when switching from standard urea to Green Urea NV®. 

The calculator enables you to: 

  • Estimate N losses under your local conditions 
  • Compare costs and benefits of upgrading 
  • Generate a customised assessment based on your crop, climate and application timing. 

The calculator is available to download on the IPF website.  
 

Further Information 

For more information, contact IPF Technical Agronomist Courtney Bills on 0447 635 653 or via email: Courtney.bills@incitecpivot.com.au  

Watch the IPF webinar discussing the “Colonsay” trials here 

Acknowledgements 

  • Trial Agronomist – Bede O’Mara, former IPF Technical Agronomist 
  • Lead Scientist – Robert Impraim, IPF R&D Agronomist 
  • Trial Support – Robert Impraim, Fiona McDonald, Elle Scannell, Natalia Gomez and Robert Bridgewater. 
  • Site Operations – Kalyx 
  • Site Cooperators – Grey Farming 

References 

  1. Barton L, Hoyle FC, Grace PR, Schwenke GD, Scanlan CA, Armstrong RD, Bell MJ (2022) Chapter One – Soil nitrogen supply and N fertilizer losses from Australian dryland grain cropping systems. In ‘Advances in Agronomy. Vol. 174.’ Ed. DL Sparks) pp. 1-52. (Academic Press) 
  1. Schwenke G (2021) “Nitrogen loss pathways. How much is lost when urea is not mechanically incorporated after application?”. GRDC, Canberra. https://bityl.co/F1KY 
  1. Schwenke GD, Manning W, Haigh BM. (2014) Ammonia volatilisation from nitrogen fertilisers surface-applied to bare fallows, wheat crops and perennial-grass-based pastures on Vertosols. Soil Research 52, 805–821. https://doi.org/10.1071/SR14107