Iris Publishers- Open access Journal of Agriculture and Soil Science | Trends in Soil Measurement Performance of
Australasian Laboratories by Methods and Time
Authored by George E Raymentc
This paper describes Australasian soil-measurement performance using
data from inter-laboratory soil proficiency programs
of the Australasian Soil and Plant Analysis Council Inc. Rapid
assessments focused only on grand median percent robust coefficients
of variation (%CVs) from 2004-05 through to 2014-15 inclusive, where
grand medians by method were calculated across 12 soil
samples annually. The %CV data were subdivided into three groupings
(2005-2008, 2009-2012, 2013-2015). For 19 soil tests, CVs
declined from 12.8% to 10.6% to 8.8%, suggestive of small improvements
in measurement quality with time. Detailed assessments
used data from 2009-10 to 2014-15 and included tests regulated for use
in “reef catchments” of North-east Australia. Relationships
between median-concentrations and associated robust %CVs were initially
assessed with power-functions, with each subsequently
solved for realistic analyte levels. Predicted trends for each method
for the six years were then plotted. From these, soil tests with
most variation were Total P, Bray-1P and Acid P. The findings confirm
improvements are needed before between-laboratories’
measurement uncertainties for the “reef-preferred” Acid P soil test
approach those for Olsen-P, Colwell-P and Mehlich-3P. Also,
measurement improvements across the six years for Mehlich-3 P exceeded
those of the other empirical soil P tests. Measurements
of Walkley-Black Organic C were disappointing in 2009-10 but improved to
2014-15. By 2014-15, soil P tests with lowest to highest
predicted robust %CVs were Mehlich-3 , Olsen P, Colwell P, Acid P and
Bray-1P, respectively. On this evidence, regulators should be
more flexible when specifying preferred diagnostic soil P tests for use
on sugarcane farms in “reef catchments.
Successive Australian and Queensland Governments for over 25 years have made policy commitments to protect The Great Barrier Reef and its Marine Park from adverse downstream effects of land uses in the river catchments of eastern Queensland that drain to the Coral Sea. The nutrients nitrogen (N) and phosphorus (P) have attracted close attention, including when used in fertilizers to grow sugarcane on around 400,000 ha of coastal soils.
Nowadays, N and P fertilizer used for sugarcane in “reef catchments” is regulated by the Queensland Government through its Environmental Protection Act 1994 [the Act] and Environmental Protection Regulation 2008; current as at 27 November 2015. Associated documentation titled “Reef Water Quality – Farming in Reef Catchments” (Environment and Heritage Protection 2016) specifies use of four soil tests to guide N and P fertilizer recommendations for plant crops of sugarcane, those being (i) Walkley and Black Organic C; (ii) Acid (BSES) P; (iii) Colwell P (when soils are alkaline); and (iv) Phosphate Buffer Index (with Colwell P). All of these plus other mentioned soil tests are described and coded byAlso specified in the Reef Water Quality documentation is a requirement that “suitable laboratories performing the chemical analysis of soil samples are required to participate in Australasian Soil and Plant Analysis Council Inc (ASPAC) proficiency trials and maintain certification for the nominated methods where available”.
Successive Australian and Queensland Governments for over 25 years have made policy commitments to protect The Great Barrier Reef and its Marine Park from adverse downstream effects of land uses in the river catchments of eastern Queensland that drain to the Coral Sea. The nutrients nitrogen (N) and phosphorus (P) have attracted close attention, including when used in fertilizers to grow sugarcane on around 400,000 ha of coastal soils.
Nowadays, N and P fertilizer used for sugarcane in “reef catchments” is regulated by the Queensland Government through its Environmental Protection Act 1994 [the Act] and Environmental Protection Regulation 2008; current as at 27 November 2015. Associated documentation titled “Reef Water Quality – Farming in Reef Catchments” (Environment and Heritage Protection 2016) specifies use of four soil tests to guide N and P fertilizer recommendations for plant crops of sugarcane, those being (i) Walkley and Black Organic C; (ii) Acid (BSES) P; (iii) Colwell P (when soils are alkaline); and (iv) Phosphate Buffer Index (with Colwell P). All of these plus other mentioned soil tests are described and coded byAlso specified in the Reef Water Quality documentation is a requirement that “suitable laboratories performing the chemical analysis of soil samples are required to participate in Australasian Soil and Plant Analysis Council Inc (ASPAC) proficiency trials and maintain certification for the nominated methods where available”.
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