Author: Dave McRae, Technical Agronomist, Incitec Pivot 


Following several seasons of strong yields across many cropping regions, soil nutrient reserves may have been significantly depleted. At the same time, ongoing uncertainty around global nitrogen (N) supply and pricing is placing greater focus on making every unit of applied N count. 

Improving N fertiliser use efficiency (NfUE) starts with understanding soil N supply, where losses may occur, and how fertiliser strategies can be adapted to better match crop demand. 

While N losses have historically been compensated for through higher application rates, minimising those losses remains a sound agronomic strategy for improving both profitability and fertiliser efficiency. 


Understanding soil N supply  

One of the most important starting points in N management is understanding how much N already exists within the soil profile and where it is located. 

Deep soil testing remains critical for accurately determining soil N supply and building reliable N budgets. 

Residual N levels can vary between paddocks and seasons depending on previous crop removal, crop rotation, mineralisation, soil moisture and seasonal conditions. 

In many regions, consecutive high-yielding crops may have significantly reduced residual soil nutrient reserves, particularly where nutrient replacement has not kept pace with removal rates.  

Dry soil profiles across parts of New South Wales and Queensland may still contain residual N reserves, while wetter or waterlogged soils are generally more susceptible to N losses through denitrification or leaching. 

Understanding this variability is important for determining realistic fertiliser requirements and avoiding unnecessary N expenditure.  

For more information on deep soil testing and N budgeting, check out:  


Matching N supply to crop demand  

N budgeting remains one of the most effective tools for improving fertiliser efficiency and profitability.  

Appropriate N rates should account for:  

  • Existing soil N supply 
  • Target yield potential 
  • Grain protein or nutrient export in harvested product 
  • Crop rotation and mineralisation potential 
  • Fertiliser uptake efficiency 
  • Expected N losses. 

Using deep soil samples, tools such as NA Pro can help estimate crop N demand more accurately and support fertiliser decision-making.   


Understanding N losses   

N losses can occur through several pathways, with the dominant loss mechanism influenced by soil type, moisture conditions, placement method and timing.  

Surface-applied urea remains particularly vulnerable to volatilisation losses when not incorporated by rainfall or tillage within 2-3 days of application. 

Schwenke (2021) found volatilisation losses from broadcast urea on Australian cropping soils averaged: 

  • 11.7% of applied N on fallow soils (range 5.4-27%) 
  • 8.1% of applied N in-crop (range 0-29%). 

Unpredictable rainfall can make timely incorporation difficult, particularly across large cropping programs. 

In heavier clay soils west of the Great Dividing Range, denitrification losses can also become significant where N is banded or applied ahead of prolonged wet conditions. In contrast, lighter textured coastal soils are generally more prone to leaching losses.  

Understanding which loss pathways are most likely within a system is important when selecting fertiliser products and application strategies. 


The role of EEFs  

Enhanced efficiency fertilisers (EEFs), including urease and nitrification inhibitors, can help reduce N losses and improve fertiliser efficiency.  

These products generally provide the greatest value where: 

  • Surface-applied urea may not be incorporated quickly 
  • Rainfall timing is uncertain 
  • Large rates of N are applied pre-plant or to the fallow  
  • Heavy textured clay soils increase the risk of denitrification losses 
  • Irrigated cotton and maize systems rely on high N inputs. 


Reducing volatilisation losses with Green Urea NV  

Green Urea NV is designed for situations where urea is surface applied without incorporation within two to three days after application. 

By reducing volatilisation losses by around 75-85%, Green Urea NV can help improve NfUE while providing greater flexibility during uncertain rainfall periods. 

This can be particularly valuable where operational constraints make rapid incorporation difficult across large, cropped areas. 

EASY N applied with streaming nozzles or streambars can also reduce volatilisation losses, trial work has shown reduced volatilisation losses compared to conventional urea applications. 

For more information, read:  


Protecting pre-plant N with eNpower  

In systems where N is banded into the soil or applied well ahead of crop demand, nitrification inhibitors can help reduce denitrification losses and maintain N availability within the soil profile. 

Products treated with eNpower are particularly suited to:  

  • Heavy textured clay soils  
  • Irrigated cotton, maize and sorghum systems  
  • Pre-plant or fallow N applications  
  • Situations where N is applied several months ahead of crop demand.  

eNpower can be used with products including urea, Gran-Am and EASY N. 

For more information, check out:  


Fine tuning N rate 

For irrigated cotton crops, monitoring the decline in petiole nitrates during the season from 600–1000 DD (base 12) or 389–651 (base 1532) can be used to alter the planned program if required.  

Nitrate N declining too quickly indicates N is running out and increased rates should be applied, while higher than optimal nitrate values indicate N fertiliser rates can be reduced. 

For more information, read:  


Making every unit count   

Improving N efficiency is not about simply reducing application rates. It’s about better matching N supply to crop demand, understanding soil nutrient reserves, and minimising avoidable losses through product choice and application strategy. 

With fertiliser markets remaining volatile and seasonal conditions variable, combining deep soil testing, sound N budgeting and enhanced efficiency fertilisers can help growers improve profitability while making every unit of N go further. 


Further information  

For further information on N budgeting, EEFs, and establishing the right strategy for your operation, please contact Incitec Pivot’s Technical Agronomist, David McRae, on 0477 987 321 or on email david.mcrae@incitecpivot.com.au.  


Reference 

Schwenke, G. (2021). Nitrogen loss pathways: How much N is lost when urea is not mechanically incorporated after application? NSW Department of Primary Industries.