This document summarizes the downscaling of GLOSOLAN proficiency tests (PTs) for soil analysis in Belgium. It describes how the REQUASUD Laboratory Network has taken over organizing PTs for routine soil laboratories, with the goals of harmonizing analytical methods, ensuring results are not dependent on the analyzing laboratory, and improving services provided by routine labs. The network now organizes 2 PTs per year for 7-8 participating routine labs, testing for parameters like pH, organic carbon, nitrogen, and heavy metals. Soil samples are prepared, distributed in duplicate to labs, and results are statistically analyzed for accuracy and reproducibility. Guidelines follow ISO standards for proficiency testing, quality control, and sample preparation.

1. Downscaling GLOSOLAN
PTs: the case of Belgium
MARIAGE Clémence
COLINET Gilles
Water Soil Plant exchanges – Gembloux ABT – Liege University
Belgium

2. REQUASUD Laboratory Network
(routine laboratories only)
Routine laboratoriesResearch institutions

3. • Some goals: harmonization of the analytical
methods, analytical results independent on the lab,
global improvement of services proposed by the
routine labs, etc
REQUASUD Laboratory Network
Organization of PTs
One of the missions written in the official agreement
(written document between all the partners of the
network)
+
The accredited labs need to participate to PTs
Routine laboratoriesResearch institutions

4. REQUASUD soil PTs
• 2 PTs per year (3 to 4 in the past)
• 7-8 participants
• 1 report by PT for all the participants (1 report/participant in the past)
• Prepared soil samples (dried and 2 mm sieved)
• Analytical parameters:
• pH, organic carbon, total nitrogen, mineral compounds (P, K, Mg, Ca,
etc), etc
• 2004: + heavy metals
• 2007: + Fe, Al and As
• 2011: + pH(water) and CEC
• 2019: + NIR method (organic carbon, total nitrogen, CEC, clay, carbonates,
humidity)
• Today: 22 in total (+ NIR)

5. REQUASUD soil PTs
• Soil samples:
• 5-6 samples duplicated
• At least 1 sample is repeated in several PTs: the participants can follow
the performance over time
• Crops, pastures, vegetable gardens, orchards, etc sampled in Wallonia

6. REQUASUD soil PTs
• Statistical tests: gross errors, Cochran and Grubbs (absurd values), repeatability,
reproducibility, accuracy
Object 1 Object 2 Object 1 Object 2 Object 1 Object 2 Object 1 Object 2 Object 1 Object 2 Object 1 Object 2 Object 1 Object 2 Object 1 Object 2
MRE2015-1 7,49 7,48 7,64 7,62 7,57 7,55 7,62 7,65 7,70 7,68 7,75 7,72 7,60 7,59 7,55 7,52
MRE2016-1 5,02 5,02 5,06 5,07 5,07 5,07 5,09 5,10 5,05 5,03 5,14 5,15 5,06 5,06 5,10 5,11
RQ20753 5,90 5,91 5,89 5,89 5,87 5,88 5,89 5,87 5,89 5,89 5,98 6,01 5,87 5,83 5,93 5,93
RQ20755 5,67 5,66 5,65 5,67 5,66 5,65 5,66 5,74 5,66 5,66 5,73 5,75 5,64 5,64 5,70 5,77
RQ20756 5,39 5,25 5,39 5,28 5,28 5,29 5,28 5,42 5,27 5,26 5,37 5,37 5,27 5,27 5,33 5,32
Labo 4 Labo 5
pH(KCl)
Labo 1 Labo 2 Labo 3 Labo 6 Labo 7 Labo 8
Repeatability
Reproducibility

7. REQUASUD soil PTs
• Guidelines:
• ISO 17043 (start working on an official accreditation in 2004 – not yet
acquired)
• ISO 13528 and ISO 5725 (for statistical treatment)
• ISO 17025 (for the preparation of the samples)
• PTs developed and improved between early 1990’s and
nowadays
• Perspectives: new parameters (to follow the new legislations/problems),
surprise PTs, more participants thanks to the official recognition (ISO 17043), etc

8. Thanks for your
attention