Proficiency Testing for Soil and Plant Analysis in Australasia

Abstract

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).

Statistical Aspects of Soil and Plant Test Measurement and Calibration in Australasia

“…On evidence compiled previously (8) and updated in Fig. 1 and Table 1, improvements in analytical performance were inconsistent, as judged by trends in robust CVs.…”

“…Soil programs from 1995 and plant programs since 1996 were processed by using nonparametric statistical procedures (8,9), noting that only outrageously deviant results (e.g., incorrect units) were removed from data sets used to derive sample population statistics on a round-by-round basis. Accordingly, the results from these were amenable to collation on a method-bymethod basis to obtain a reasonable estimate of robust coefficients of variation (CV) for known concentrations.…”

“…Indeed, concentrations of 10,000, 100, 1, 0.1, and 0.01 mg kg 21 have predicted CVs of 4%, 8%, 16%, 23%, and 32%, respectively. In practice, most soil and plant chemical tests performed across Australasian laboratories have fallen outside these variances, despite efforts by the Australasian Soil and Plant Analysis Council Inc (ASPAC) to improve measurement performance (8). How the samples are collected, transported, and prepared for analysis adds to the uncertainty.…”

Initiatives of the Australasian Soil and Plant Analysis Council to Assess the Measurement Quality of Common Methods for Soil and Plant Analysis in Australasia

“…Indeed, the test was already being offered routinely in Western Australia and (together with additional attributes obtained from the Mehlich 3 extract) was being evaluated in the catchments of coastal Queensland that drain to the Great Barrier Reef World Heritage Area (Rayment 2004;Bloesch and Rayment 2006). Van Vuuren, van Dijk, and Claassens (2002) had earlier reported the value of cooperation between different proficiency program providers (WEPAL and AgriLASA), while Rayment and Peverill (2002) compared the measurement performance of total plant nitrogen, phosphorus, and calcium from Australasian laboratories relative to others in selected WEPAL programs.…”

Phosphorus Fertility Assessment of Intensively Farmed Areas of Catchments Draining to the Great Barrier Reef World Heritage Area; 1: Soil Phosphorus Status

“…In addition, some soils would have received mill mud applications. Alternatively or in addition, sampling and/or laboratory measurement error may be implicated (Rayment and Peverill 2002). Of these two additional possibilities, sampling error associated with soil variability seems more likely, as the analyses were undertaken in the same laboratory by the same method.…”