1) The Australasian Soil and Plant Analysis Council (ASPAC) was formed in 1990 to enhance soil and plant analysis standards across laboratories through regular proficiency programs. 2) ASPAC oversees proficiency testing involving approximately 50 soil tests from 10-52 participating laboratories in Australia, New Zealand, and parts of Asia. 3) Laboratories must incur no more than 4 demerit points from testing 12 soil samples per year, with 2 points given for outliers and 1 for results outside 2 standard deviations, to receive ASPAC proficiency certification for specific soil tests.

1. Value of a PT – a Case Study
Rob De Hayr

2. One of the main reasons why the Australasian Soil and Plant
Analysis Council Inc. (ASPAC) was formed in 1990
“conduct regular Quality Assurance Programs to enhance standards
of the analysis and assist standardisation of soil and plant analytical
methods across laboratories”.
ASPAC’s Laboratory Proficiency Committee (ASPAC LPC) overviews
the programs
Global Proficiency Ltd (GPL) is the external provider using ASPAC
developed procedures
Technical Advisory Group (TAG) was established in 2004/5 with
membership from GPL and the ASPAC LPC

3. Soil Testing Proficiency
Approx. 50 tests certifiable
depending on test, 10-52
labs provide results
total of 59 labs, including
Australia, New Zealand,
all Pacific Islands and
some SE Asian

4. 0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
40.0
MedianRobustCV's Change in Lab Performance overTime (Soils)
2005-07 2009-11 2013-15

5. ASPAC soil proficiency performance
Best (Lowest Robust %CVs)
Soil Method %CV
Soil pH, 1:5 0.01 M CaCl2 (4B1) 1.8
Soil pH, 1:5 0.01 M CaCl2 (4B2) 1.8
Soil pH, 1:5 H2O (4A1) 2.2
Exch. Ca, NH4Cl (15A1) 3.7
EC, 1:5 water (3A1) 4.2
Total Org. C (6B1 + 6B2 +6B3) 5.4
Exch. Mg, NH4Cl (15A1) 6
Exch. K, NH4Cl (15A1) 6.5
Exch. Mg, NH4OAc (15D3) 7.6
Total N (pooled 7A1 + 7A2) 7.9

6. ASPAC soil proficiency performance
Worst (Highest Robust %CVs)
Soil Method %CV
Meh 3 Extr. Fe (18F1) 21.5
Meh 3 Extr P (18F1) 21.5
Meh 3 Extr Zn (18F1) 22
Water Sol. Cl Auto –Color. (5A2) 22.5
Meh 3 Extr S (18F1) 23
Bray – 1 Extr. P (9E1 + 9E2) 25
Meh 3 Extr Cu (18F1) 29
Water Sol. Cl Potent. (5A1) 35.5
Exch. Al KCl (15G1) 79.5
Meh 3 Extr B (18F1) 81.5

7. -5
-4
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10181 21190 21215 21234 50006 50014 50038 52673 52676 52700
ASS2006-1
ASS2006-2
ASS2006-3
ASS2006-4
-5
-4
-3
-2
-1
0
1
2
3
4
5
10181 21104 21190 21215 21234 50006 50014 52673 52676 52700
ASS2003-1
ASS2003-2
ASS2003-3
ASS2003-4
-5
-4
-3
-2
-1
0
1
2
3
4
5
10181 21190 21234 50014 50038 52676 21104 50002
ASS2009-1
ASS2009-2
ASS2009-3
ASS2009-4
pH (1:5 Water)
Mar 2020
Jun 2020
Sep 2020
Oct 2019

8. -5
-4
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0
1
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10181 21104 21190 21234 50002 50014 50038 52673
ASS2009-1
ASS2009-2
ASS2009-3
ASS2009-4
-5
-4
-3
-2
-1
0
1
2
3
4
5
10181 21190 21234 50006 50014 50038 52673 52676 52700
ASS2006-1
ASS2006-2
ASS2006-3
ASS2006-4
-5
-4
-3
-2
-1
0
1
2
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4
5
10181 21104 21190 21234 50006 50014 52673 52676 52700
ASS2003-1
ASS2003-2
ASS2003-3
ASS2003-4
EC (1:5 Water)
Mar 2020
Jun 2020
Sep 2020
-5
-4
-3
-2
-1
0
1
2
3
4
5
10181 21104 21190 21234 50002 50006 50014 50038 52676
ASS1909-1
ASS1909-2
ASS1909-3
ASS1909-4
Oct 2019

9. Exchangeable K
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10181 21104 21190 21234 50006 50014 50038 52623 52676
ASS1909-1
ASS1909-2
ASS1909-3
ASS1909-4Oct 2019
-5
-4
-3
-2
-1
0
1
2
3
4
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10181 21104 21190 21234 50006 50014 52673 52676
ASS2003-1
ASS2003-2
ASS2003-3
ASS2003-4
-5
-4
-3
-2
-1
0
1
2
3
4
5
10181 21190 21234 50006 50014 50038 52673 52676
ASS2006-1
ASS2006-2
ASS2006-3
ASS2006-4
Mar 2020
Jun 2020
-5
-4
-3
-2
-1
0
1
2
3
4
5
10181 21190 21234 50014 50038 52673 50002
ASS2009-1
ASS2009-2
ASS2009-3
ASS2009-4
Sep 2020

10. -5
-4
-3
-2
-1
0
1
2
3
4
5
10181 21190 21234 50014 50038 52673 52676 50002
ASS2009-1
ASS2009-2
ASS2009-3
ASS2009-4
-5
-4
-3
-2
-1
0
1
2
3
4
5
10181 21190 21215 21234 50014 50038 52673 52676
ASS2006-1
ASS2006-2
ASS2006-3
ASS2006-4
-5
-4
-3
-2
-1
0
1
2
3
4
5
10181 21190 21215 21234 50014 52673
ASS2003-1
ASS2003-2
ASS2003-3
ASS2003-4
-5
-4
-3
-2
-1
0
1
2
3
4
5
10181 21190 21215 21234 50002 50014 52623
ASS1909-1
ASS1909-2
ASS1909-3
ASS1909-4
Olsen P
Mar 2020
Jun 2020
Sep 2020
Oct 2019

11. -5
-4
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-2
-1
0
1
2
3
4
5
21190 21234 50014 50038 52673 21104 50002
ASS2009-1
ASS2009-2
ASS2009-3
ASS2009-4
-5
-4
-3
-2
-1
0
1
2
3
4
5
21190 21215 21234 50006 50014 50038 52673 52676
ASS2006-1
ASS2006-2
ASS2006-3
ASS2006-4
-5
-4
-3
-2
-1
0
1
2
3
4
5
21190 21215 21234 50006 50014 52673 52676
ASS2003-1
ASS2003-2
ASS2003-3
ASS2003-4
OC (W&B)
Mar 2020
Jun 2020
Sep 2020
-5
-4
-3
-2
-1
0
1
2
3
4
5
21104 21190 21215 21234 50002 50006 50014 50038 52623
ASS1909-1
ASS1909-2
ASS1909-3
ASS1909-4
Oct 2019

12. Some Observations of issues
• Reporting in the incorrect units
• Incorrect converting of data e.g.
• mg/kg to cmol(+)/kg
• µS/cm to dS/m
• Incorrect methods used and reported - remember the
“Green Book” methods are the reference for methods
reported in the ASPAC Interlaboratory Proficiency Program
e.g. different soil:solution ratios
The methods you report need to be verified and validated

13. ASPAC proficiency certification
• In SoilChek each laboratory tests 12 soil samples
per year, consisting of 3 rounds of 4 samples each.
• The scoring system involves allocation of demerit
points for each sample on the basis of the z-score
result obtained from method specific statistical
analysis.
• Method specific certification is given when a
laboratory incurs no more than 4 demerit points for
the 12 samples.

14. • For each test method:
• 2 demerit points are allocated to a statistical
outlier (ASPAC Score >2 at the first iteration ), or if
no result submitted.
• 1 demerit point is allocated to a statistical
straggler (ASPAC Score >2 at the second
iteration).
• A maximum of 3 demerit points are accrued per
round, so that no single poor performing round
will incur a laboratory’s certification failure.
ASPAC proficiency certification

15. Thanks for your
attention