Calibration of the commercial soil test for P on a red calcareous loam

2019

Research organisations
Funding source

Trial details

Researcher(s) Sjaan Davey
Ian Richter
Nigel Wilhelm
Year(s) 2019
Contributor SARDI Minnipa Agricultural Centre
Trial location(s) Minnipa, SA
Calibration of the commercial soil test for P on a red calcareous loam locations
Aims

Soil testing for N, P, K and S is a key strategy for monitoring soil fertility of cropping soils as well as for refining fertiliser application strategies for future crops. For this to be successful, the relationship between the soil test and likely response to applied nutrients needs to be well calibrated. Many of these calibrations were developed from fertiliser trials conducted over 20 years ago and have provided robust guidelines on many soil types, but mostly for cereals. Since these trials were conducted cropping systems have changed significantly and altered the face of soil fertility in the Australian grains industry. A detailed re-examination of those existing guidelines is needed to ensure they are still relevant in current farming systems.

As part of the GRDC funded MPCN2 (More Profit from Crop Nutrition) program, a review of data in the Better Fertilizer Decisions for Cropping (BFDC) database showed gaps exist for key crops, soils and regions. Most of these gaps relate to crops that are (i) new to cropping regions or are a low proportion of cropped area, i.e. break crops, (ii) emerging nutrient constraints that had previously been adequate in specific soil types and (iii) issues associated with changing nutrient profile distribution. This project (UQ00082) is closing gaps in the BFDC database using replicated trials. Trials have been established on sites selected for nutrient responses and run over multiple years to develop soil test-crop response relationships. By using wheat as a benchmark alongside a break crop, we should be able to extend the relevance of the guidelines beyond the conditions at the trial site.

Key messages
  • With low rainfall and poor growth at many sites, crops required little P to maximise grain yield.
  • On a red sandy clay loam at Minnipa, wheat only needed a Colwell P value of 10-15 mg/kg to achieve maximum grain yield without P fertiliser.
  • Canola appears to have a lower critical P level than wheat.
Minnipa SA 2019 Canola

Paddock history 2018: Wheat before canola, canola before wheat trial 2017: Pasture 2016: Pasture 2015: Pasture

Soil type Red sandy clay loam

Soil test pH(H20) 8.4, PBI 79, K 523 mg/kg

Plot size 20 m x 2 m x 4 reps x 25.5 cm row spacing

Trial design Completely randomised design, 2 bays deep x 44 plots long x crop type (wheat or canola)

Yield limiting factors Low rainfall, frost

Minnipa SA 2019 Wheat

Paddock history 2018: Wheat before canola, canola before wheat trial 2017: Pasture 2016: Pasture 2015: Pasture

Soil type Red sandy clay loam

Soil test pH(H20) 8.4, PBI 79, K 523 mg/kg

Plot size 20 m x 2 m x 4 reps x 25.5 cm row spacing

Trial design Completely randomised design, 2 bays deep x 44 plots long x crop type (wheat or canola)

Yield limiting factors Low rainfall, frost

Lead research organisation South Australian Research and Development Institute
Host research organisation SARDI Minnipa Agricultural Centre
Trial funding source GRDC UQ00082
Related program N/A
Acknowledgments

Mike Bell (The University of Queensland) who leads the UQ00082 project funded by GRDC. Thank you to Neil King, Katrina Brands, Steve Jeffs and Bradley Hutchings for undertaking the field work and processing samples


Other trial partners SARDI Waite Campus
Download the trial report to view additional trial information

Method

Crop types Oilseed: Canola Cereal (Grain): Wheat
Treatment type(s)
  • Crop : Type
  • Soil
  • Soil : Testing method
Trial type Experimental
Trial design Randomised,Replicated

Minnipa 2019 Canola

Sow date Not applicable
Harvest date Not applicable
Trial design method CRD Completely Randomised Design
Plot size 20m x 2m
Plot replication 4
Plot blocking Random
Plot randomisation Y

Minnipa 2019 Wheat

Sow date Not applicable
Harvest date Not applicable
Trial design method CRD Completely Randomised Design
Plot size 20m x 2m
Plot replication 4
Plot blocking Random
Plot randomisation Y
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
Minnipa, SA Red sandy clay loam
Derived trial site soil information
Australian Soil Classification Source: ASRIS
Trial site Soil order
Minnipa, SA Calcarosol
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 Minnipa SA
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Climate

Derived climate information

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

Minnipa SA

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

SILO weather estimates sourced from https://www.longpaddock.qld.gov.au/silo/
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 report and links

2019 trial report



Trial last modified: 07-10-2025 18:52pm AEST