Proficiency testing programs are essential for ensuring consistency and accuracy in soil analysis across different laboratories, particularly in Australia, where variations in soil testing results have historically been problematic. The Australasian Soil and Plant Analysis Council (ASPAC) established an inter-laboratory proficiency program (ILPP) to improve lab performance through benchmarking and statistical assessments of test results. These programs benefit participating labs by enhancing their testing capabilities, providing quality assurance, and promoting continuous improvement.

1. Why are Proficiency Testing Programs useful?

2. Background Some perspectives from Australia
• Soil analyses are used in many agricultural systems to guide
fertiliser inputs
• Broad acre grains (wheat, barley, sorghum, maize)
• Sugarcane
• Dairy

3. Background Some perspectives from Australia
• Fertiliser inputs must be
o profitable for the farmer
o environmentally responsible
For example, to protect the water quality of the
Great Barrier Reef in tropical north Queensland,
government legislation requires fertiliser
application rates to be based on
- yield targets for nitrogen
- soil analyses for phosphorus and potassium

4. Background Some perspectives from Australia
• In the early 1990’s, a newspaper reported that when a
soil sample was sent to several labs for analysis,
different results were reported for the same soil test.
• This prompted ASPAC (Australasian Soil and Plant Analysis
Council) to set up an Inter-Laboratory Proficiency Program
(ILPP) for soil and plant analysis to benchmark and improve
cross-lab performance.
• The ILPP includes a certification scheme to allow labs to
demonstrate that they are providing results consistent with
other labs providing that analysis

5. What is a Proficiency Testing Program?
• Labs may have accreditation for following prescribed
QA/QC processes and procedures, but this does not
demonstrate that they would obtain a similar result as other
abs for a soil test
QA/QC accredited labs
(e.g., ISO/IEC 17025)
For example: Soil test A results
Proficiency certified labs

6. What is a Proficiency Testing Program?
The basic requirements for a Proficiency Testing Program are:
• Homogenised bulk soil samples are periodically distributed
to participating labs and analysed for a specified soil method
according to its Standard Operating Procedure.
• Lab results (anonymous) are reported to a central
technical panel responsible for undertaking statistical analyses
to calculate the median value and confidence intervals for the
soil test.
• Lab results are classified as ‘acceptable’, ‘straggler’ or
‘outlier’, and demerit points applied for any stragglers/outliers.
• The lab is certified if it produces soil test results that are
consistently within the confidence intervals for the soil test
median value.

7. What are the benefits of a Proficiency Testing
Program?
• Assists in maintaining/increasing your current level of
soil testing capacity.
• Increases your confidence to carry out standard soil test
methods.
• Provides a cost-effective quality assurance program to
participants.
• Indicates your current level of proficiency to existing and
prospective clients.
• Allows for continuous improvement in lab performance
by benchmarking and interaction with other labs
carrying out the same analyses.

8. Some observations from the ASPAC ILPP
• Approximately 60 labs participate: ≈40 Australia,
≈7 New Zealand, ≈10 south-east Asia and south Pacific
Most commonly reported soil methods are:
soil pH (1:5 water); soil EC (1:5 water); Walkley-Black
organic C; Colwell-P; Olsen-P; NH4OAc-extractable K;
DTPA-extractable Cu, Zn, Fe and Mn
• Each certification round comprises 3 dispatches of
4 soil samples each over a 12 month period

9. Rayment GE, Lyons DJ, Hill RJ (2017) ASPAC Soil Testing Proficiency Program Report 2011-12
Some observations from the ASPAC ILPP
• Coefficient of variation differs between soil tests
e.g., %CV of Olsen-P and Bray P1 over 3 years
• Evidence of proficiency improvement in Olsen-P, but not
Bray-P1

10. The way forward for SEALNET
• The ‘ASEAN Guidelines on Soil
and Nutrient Management’ identify the
importance of a regional lab proficiency
testing program
Now is the time to implement a lab proficiency
testing program!

11. Thank you for your attention…