Outcomes of EEF60 - Cane farmer trials and modelling of enhanced efficiency fertilisers (Reef Trust and GBRF)

The project tested DMPP treated urea in 65 trials on 25 sites over four seasons. Mean cane and sugar yield in tonnes per hectare (tch and tsh) and net revenue in dollars per hectare ($/ha) results are presented in Figure 1.

Cane yield and CCS data were collected from local sugar mills and used to calculate sugar yield and profitability. Results were analysed to identify differences in cane yield, sugar yield and grower profitability.

Figure 1: Mean cane yield (tch), sugar yield (tsh) and net revenue ($/ha) over four ratoons for 65 trials where urea (at 6ES and 20% less) was compared to DMPP treated urea applied at 20% less. P<0.05, means followed by a common letter are not significantly different at the 5% level.

Field trials demonstrated that EEFs when applied at N rates 20% below SIX EASY STEPS guidelines can reduce nitrogen losses by better matching N supply with crop demand whilst maintaining productivity and profitability.

Modelling by CSIRO was undertaken with the aim of providing information (using APSIM farming systems model) on the expected benefits of EEFs in both time and space to inform when and where using EEFs in place of urea could deliver N loss reductions that can be expected in the Wet Tropics

Key findings from field trials and modelling included*:

• Generally, applying urea at 20% less than the SIX EASY STEPS N guidelines results in a small but significant loss in cane yield and industry income. Yield losses were more likely in medium and high rainfall conditions and less likely in low rainfall conditions earlier in the season.
• Generally, applying DMPP treated urea at 20% less than the SIX EASY STEPS recommended N rate with urea maintains yield and profitability but also improves NUE.
• Generally, applying a CRF blended with urea (20% CRF and 80% urea) at 20% less than the SIX EASY STEPS recommended N rate with urea maintains yield and profitability but also improves NUE.
• Crop modelling indicated that the risk of N losses was mostly associated with late season fertiliser application in drier regions and mid-late season fertiliser application in very wet regions of the Wet Tropics.
• Both field trials and modelling showed EEFs were more effective when high loss conditions were experienced, particularly late in the season.
• In-field experiments identified that this was particularly the case on sandy soils, when receiving high rainfall and fertilised late in the season. Whereas crop modelling data in the Wet Tropics suggested EEF application late in the season may potentially have positive yield impacts in some situations due to their ability to reduce N losses.
• Higher than average urea prices improve the cost-competitiveness of using DMPP and blended CRF products (20% CRF 80% Urea) when applied at N rates 20% below the SIX EASY STEPS recommendation.

*Results at individual sites may vary from these general findings

For growers interested in utilising EEFs, consider the following recommendations:

• For DMPP and blended CRF products (20% CRF 80% Urea), use an N rate 20% below the SIX EASY STEPS recommendation as this should maintain productivity and profitability.
• Limit use of CRF blends with a higher proportion of CRF (greater than 20%) as this results in lower grower profitability due to higher fertiliser costs.
• Use EEF products when high N loss conditions are expected, particularly late season fertiliser application. In very wet regions, growers could target mid-late fertiliser application times.
• Use of EEF’s at the lower N rate is generally applicable to most growing conditions and with experience growers could expand their use. Although, application of EEF’s early in the season is less likely to provide benefit as N losses are not as likely.
• Take advantage of the improved cost-competitiveness of DMPP and blended CRF products (applied at 20% less N) when urea prices are higher than average.
• It is recommended that any change in management is tested on-farm. This will build confidence in both the new nutrient rates/products but also aid the process of fine tuning a nutrient management program as part of STEPS 5 & 6 in SIX EASY STEPS. A guideline for conducting on-farm trials is included in the SIX EASY STEPS Toolbox.

A detailed project summary, key messages, and case studies for three regions can be accessed.

A summary of CSIRO’s modelling work is included in the Wet Tropics booklet.

Results of enhanced efficiency fertiliser trials in the catchments of the great barrier reef includes case studies and modelling outcomes from the Wet Tropics

Results of enhanced efficiency fertiliser trials in the catchments of the great barrier reef includes case studies from Mackay/Whitsundays

Results of enhanced efficiency fertiliser trials in the catchments of the great barrier reef includes case studies from the Burdekin

WEBINAR: Innovations in cane growing and farm management hosted by the Great Barrier Reef Foundation, May 2023

The on-ground testing and modelling of the effectiveness of enhanced efficiency fertilisers in the Wet Tropics catchments of the Great Barrier Reef project was funded by the partnership between the Australian Government’s Reef Trust and the Great Barrier Reef Foundation with support from a collaborative partnership between Sugar Research Australia, Department of Agriculture and Fisheries, CSIRO, CANEGROWERS, productivity services and cane farmers.

Papers published from the Australian Society of Sugar Cane Technologists annual conference are also available at www.assct.com.au

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