Proficiency testing for soil and plant analysis in Australasia

The Australasian Soil and Plant Analysis Council Inc (ASPAC) has coordinated regular inter-laboratory proficiency programs separately for soil and plant samples since the early 1990's. Certification of proficiency to perform specific tests depended on the demerit points accrued for the test in the particular program, without heed to historical performance. In addition to describing local ad hoc initiatives to enhance soil and plant analytical quality, this paper provides feedback on longer-term laboratory performance, based on reported results for eight tests in the four most recent ASPAC plant inter-laboratory proficiency programs (20 laboratories) and the three most recent ASPAC programs for soils (12 laboratories). Laboratories were subsequently. rated as Category 1 through to Category 4 (best to least-well performed). None of the 20% of laboratories rated as Category 1 for plants received a similar rating for soils, although 4 laboratories achieved at least a Category 2 rating for their combined soil and plant analytical performance over several years. Additionally, there was reasonable agreement between "as reported" median values for a selection of plant tests from five randomly selected Australasian laboratories (two from New Zealand and three from Australia) and "final" median values for the same samples and tests as documented in the 1999 Bi-monthly and the 2000 Quarterly International Plant Analytical Exchange Program reports from Wageningen. Similar international comparisons were not undertaken for soils because of differences in much of the methodology.