Author: David McRae, Technical Agronomist, Incitec Pivot

Maximising cotton lint yield while improving nitrogen use efficiency (NUE) is a key challenge for cotton growers. Soil conditions, fertiliser placement and root development all play an important role in determining how efficiently crops use applied nitrogen (N) and ultimately, their performance and yield.

Growers can improve NUE and maximise lint yield by:

  • matching N supply to crop demand,
  • optimising fertiliser placement,
  • minimising irrigation-related losses and
  • using enhanced efficiency fertilisers (EEFs) where they provide an economic benefit.

Careful fertiliser budgeting is an important part of this process, and there are several practical steps growers can take to protect their N investment.

Soil testing is essential

Pre-plant soil testing at segmented depths is one of the most valuable tools you can use to ensure efficient and profitable use of available N. It provides the information you need to create a fertiliser budget that matches N supply to cotton N demand, in the process improving NUE. Ultimately, it enables you to focus on the 4Rs of nutrient management – right product, right time, right place, right rate.

In season, petiole N testing at key growth stages can be used to check the adequacy of budgeted N rates so you can adjust during the season if required.

Soil and petiole testing are available through the Nutrient Advantage Laboratory.

Protect pre-plant N with eNpower®

If pre-season soil testing confirms additional N is required, one of the most effective ways to protect your N investment is with enhanced efficiency fertilisers (EEFs) like Incitec Pivot’s eNpower®. eNpower® is granular Urea coated with Incitec Pivot’s patented nitrification inhibitor, which slows the conversion of ammonium to nitrate in the soil.

Industry research has proven that applying excessive rates of N can lead to lower NUE and result in significant losses of N as greenhouse gases such as nitrous oxide (N2O).

To demonstrate how EEFs like eNpower® can prevent N losses, Incitec Pivot conducted a replicated field study to measure the yield benefit of using pre-plant N treated with eNpower® in irrigated cotton and maize. Results from both cotton and maize sites showed that yield can be maintained whilst reducing total applied N (pre-plant and in crop) by a measure of 50 kg/ha N when the applied urea was treated with eNpower®.

This aligns with recent research that indicated substantial scope to improve fertiliser NUE and reduce N losses (N2O and di-nitrogen (N2)) in cotton without any impact on lint yield, by adjusting N fertiliser application rates in combination with the use of the nitrification inhibitor dimethylpyrazole(DMP), such as eNpower® (Scheer et al. 2022).

Managing N loss is key in cotton systems – using eNpower® within a broader N strategy – helps keep more N available in the soil when crops need it, improving efficiency and supporting sustainable production.

For growers using anhydrous ammonia, eNpower Ammonia® is an option to prevent N loss during pre-plant applications. eNpower Ammonia® is a nitrification inhibitor that can be injected into anhydrous ammonia during application.

Root system development

A key consideration for fertiliser application is the way cotton root systems develop throughout the growing season. Research has shown root density can effectively double as crops progress through critical growth stages (Hulugalle et al. 2015). This growth coincides with periods of rapid nutrient demand. Between first flower and peak flowering, cotton takes up around 40% of its N requirement, while more than half of total N uptake occurs between first squares and peak flowering. These findings reinforce the importance of ensuring N is available when crop demand is greatest.

In-crop N protection options

Surface-applied fertiliser is common in summer but managing N loss is critical. Incitec Pivot trials have shown that volatilisation from surface applied N can account for up to 5-30% of applied N. Green Urea NV® is a proven urease inhibitor that helps protect topdressing applications of N by preventing losses through volatilisation.

It is a spray-on coating which slows the activity of a specific biological process involved in the conversion of urea to ammonium. This gives time for urea to be incorporated by inter-row cultivation, rain or irrigation, resulting in less losses and more retention of N in the system for crop production. It also means Green Urea NV® gives more control over fertiliser application timing. It can be applied ahead of rain by up to 14 days without the stress of needing to incorporate it immediately. 

Another option to mitigate N loss is EASY Liquids N26®, a urea-based liquid fertiliser designed for water run application. Its non-polar formulation ensures even application throughout the furrow, moving efficiently into the root zone with irrigation water, allowing rapid N uptake. This application method minimises N losses from volatilisation and synchronises N availabilities with peak crop demand, reducing potential denitrification losses.

Summary

Pre-plant soil testing and in-season petiole testing can help growers accurately match N supply to crop demand, improving nitrogen use efficiency (NUE) and supporting the 4Rs of nutrient management: right product, rate, time and place.

Products such as eNpower® and eNpower Ammonia® help reduce N losses by slowing nitrification. Research and field trials show growers can maintain cotton lint yields while reducing N application rates and lowering greenhouse gas emissions.

Cotton’s N requirements increase significantly from first flower through to boll development, when most N uptake occurs. Effective fertiliser strategies should ensure N is available during these critical growth stages.

Surface-applied N can lose 5-30% of applied N through volatilisation. Products such as Green Urea NV® and EASY Liquids N26® help retain more N in the root zone, improve uptake efficiency, and better align nutrient availability with peak crop demand.

Further information

For more information and to discuss N management strategies in cotton, contact:

  • David McRae – Incitec Pivot Technical Agronomist: 0477 987 321
  • Courtney Bills –Incitec Pivot Technical Agronomist: 0447 635 653
  • Matt Urquhart – EASY Liquids, Moree: 0429 789 298
  • Bob Moorfield – EASY Liquids, Whitton: 0488 067 736