Variable rate technology case study 2015

CC BY 4.0

Research organisatons
Funding source

Trial details

Researcher(s) Erin Cahill (agVivo)
Bindi Isbister (Precision Agriculture)
David Isbister (Homewood Farms)
Year(s) 2015
Contributor West Midlands Group
Trial location(s) Dandaragan, WA
Variable rate technology case study 2015 locations

Demonstrate variable rate technology on farm and how it can be applied to manage fertiliser use and to minimise nutrient enrichment or depletion that leads to poor soil health.

Key messages

This year there was no big benefit from variable rate fertilizer in relation to yield. This is not unexpected given the dry season.

This trial gives some confidence that cutting fertilizer in particular P back on the low zone did not impact yield and had the best gross margin, therefore is a good strategy to reduce costs on the lower performing parts of the paddocks. This is consistent with current DAFWA and GRDC research findings that less phosphorus can be applied on soils with good P history without penalizing yield. Similarly it demonstrated the potential to reduce rates on the higher production zones depending on the season as tissue tests indicated adequate nitrogen just prior to the late N application. It is likely there was also more nitrogen available as a result of ripping increasing nitrogen mineralization and plant root access to water and nutrients. Reducing N applied after ripping is a recommended strategy to reduce the risk of the producing high biomass and the crop haying off early with a dry finish.

The estimated yield potential of the zones was not reached with the high zone about 1.5 t/ha below potential. This is consistent with farm observations that found there was a penalty of about 1 t/ha for crops sown later than 7 days from the 22nd May crops in this dry season.

High resolution six meter imagery was found to be very useful to identify management issues and map non-wetting soils, particularly the early July image which highlighted emergence issues. The non-wetting areas can be mapped and treated by ploughing those areas paddock not the whole reducing the cost of treatment. Ground-truthing showed the 6m resolution was high enough to identify problems with the bar such as running out of fertilizer. These are management issues that can be adjusted to improve efficiency and production to improve yield. 

In the case study paddock the imagery has highlighted issues that were not evident from the yield maps such as residual compaction from old corners and where the ripper and spader lifted over a water pipe (the red line in the top north east corner). This paddock has been deep ripped twice but old compaction is still visible suggesting it is beyond the current ripping depth of 400mm. The late season imagery was too late to see any big differences in biomass. An optimal time to capture imagery appears to be mid-July.

Applying low fertilizer to the low production zone is both a good economic strategy to improve profitability and prevents over fertilizing that increases the risk of nutrient leaching in these pale sands that have limited capacity to store nutrients.

Lead research organisation Precision Agriculture Pty Ltd
Host research organisation West Midlands Group
Trial funding source Australian Government
Related program N/A

This project “Engaging our community to improve soil health in the West Midlands” is supported by West Midlands Group, through funding from the Australian Government’s National Landcare Program.

Other trial partners Not specified
Download the trial report to view additional trial information


Crop type Barley
Treatment type(s)
  • Fertiliser
Trial type Demonstration
Trial design Replicated

Dandaragan 2015

Sow rate or Target density 75kg/ha
Sowing machinery

CaseIH Header, Ausplow DBS seeder, Ausplow multistream airseeder cart, Cat Tractor with JD guidance.

Sow date 29 May 2015
Harvest date Not specified
Plot size Not specified
Plot replication Not specified

The paddock was deep ripped in March to 420mm. Seeding fertilizer KtillMOP blend (KTILL EXTRA 80%, MOP 11% and MAP 9%) with Flexi N 20L/ha Hi Load with flexi N = 150ml/ha applied as per rates in Table 1. 1st post emergent N application 80kg/ha NS 3:1 washed in on the 6/7/15. 2nd Urea application washed in 7/8/15.


glyphosate 1.5l oxyflufen 0.1l, ester 680 0.25l, Sprayseed 1l trifluralin 1.8l, metribuzin 0.08l, Paragon 0.05l, BROM MA 0.5l


Insecticides chlorpyrifos 0.3l


Fungicides Tilt 0.4 l and Prosaro 0.15l

Download the trial report to view additional method/treatment information
Trial source data and summary not available
Check the trial report PDF for trial results.
Observed trial site soil information
Trial site soil testing
Not specified
Soil conditions
Trial site Soil texture
Dandaragan, WA Yellow sandplain
Derived trial site soil information
Australian Soil Classification Source: ASRIS
Trial site Soil order
Dandaragan, WA Tenosol
Soil Moisture Source: BOM/ANU
Average amount of water stored in the soil profile during the year, estimated by the OzWALD model-data fusion system.
Year Dandaragan WA
2015 103.9mm
2014 94.8mm
2013 121.8mm
2012 132.3mm
2011 96.9mm
2010 84.2mm
2009 110.1mm
2008 97.5mm
2007 51.3mm
2006 74.4mm
2005 95.5mm
2004 91.7mm
2003 90.5mm
2002 32.9mm
2001 35.4mm
2000 114.0mm
National soil grid Source: CSIRO/TERN
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



Dandaragan WA 2015

Observed climate information

Rainfall trial gsr (mm) 303mm

Derived climate information

Dandaragan WA


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.

Trial last modified: 23-07-2019 14:25pm AEST