Variable rate nitrogen


Research organisaton
Funding source

Trial details

Researcher(s) Nicole Dimos (SPAA), Felicity Turner (Vision Ag) and Grant Yates
Year(s) 2011
Contributor Society of Precision Agriculture Australia
Trial location(s) Site 2, Coonalpyn , SA
Variable rate nitrogen locations

To compare the effects of variable rate nitrogen applications on wheat yield across varying soil types.

Key messages

The trial has indicated that the application of the high rate UAN (140L/ha) over the entire paddock still proved to be a more profitable than applying the low rate over the entire paddock, however the overall gross margin benefits are not as visible due to the low yielding sand zone only occupying 9ha (13%) of the paddock. However these results confirm that the adoption of PA is an economically sound decision, indicating that the grower could make a saving of $48/ha if that extra nitrogen was not applied to the low yielding area via the use of variable rate fertiliser application. The trial results have solidly indicated that the overall gross margin would be profitably affected not having to spend the extra $62/ha on fertiliser. The gain of $53/ha in the high yield zone with high rate N (140L) is a substantial increase in profit over the low rate (60L) showing there is benefits to adding N in these zones.

Lead research organisation Society of Precision Agriculture Australia
Host research organisation N/A
Trial funding source GRDC SPA000010
Related program N/A

This project was funded by the Grains Research and Development Corporation (GRDC)

Other trial partners AAron and Trent Long (property owners)
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Crop type Wheat
Treatment type(s)
  • Fertiliser: Rate
  • Soil: Type
Trial type Precision agriculture
Trial design Not applicable

Coonalpyn 2011

Sow rate or Target density 80 kg/ha
Sow date 14 May 2011 14 May 2011
Harvest date Not specified
Plot size Not specified
Plot replication Not specified

Variable rate UAN

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Download results

Trial results Table 1

# Treatment 1
Treatment 2
Grain yield (t/ha)
1 Low yield zone (sand) UAN @ 140 L/ha 1.62
2 Low yield zone (sand) UAN @ 60 L/ha 1.56
3 Low yield zone (gravel) UAN @ 140 L/ha 3.02
4 Low yield zone (gravel) UAN @ 60 L/ha 2.61
5 Medium yield zone UAN @ 140 L/ha 3.23
6 Medium yield zone UAN @ 60 L/ha 2.98
7 High yield zone UAN @ 140 L/ha 3.78
8 High yield zone UAN @ 60 L/ha 3.28

Grain yield t/ha

Observed trial site soil information
Trial site soil testing
Not specified
Soil conditions
Trial site Soil texture
Site 2, Coonalpyn , SA Not specified
Derived trial site soil information
Australian Soil Classification Source
Trial site Soil order
Site 2, Coonalpyn , SA Calcarosol
National soil grid Source
NOTE: National Soil Grid data is aggregated information for background information on the wider area
Actual soil values can vary significantly in a small area and the trial soil tests are the most relevant data where available

Soil properties



Derived climate information

No observed climate data available for this trial.
Derived climate data is determined from trial site location and national weather sources.

Site 2, Coonalpyn SA

NOTE: Exact trial site locality unknown - Climate data may not be accurate

Some data on this site is sourced from the Bureau of Meteorology

SILO weather estimates sourced from
Jeffrey, S.J., Carter, J.O., Moodie, K.B. and Beswick, A.R. (2001). Using spatial interpolation to construct a comprehensive archive of Australian climate data , Environmental Modelling and Software, Vol 16/4, pp 309-330. DOI: 10.1016/S1364-8152(01)00008-1.

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Trial last modified: 30-09-2019 16:11pm AEST