Title: Wet Aggregate Stability Index: Precision Assessment of Tiulin Method Trough an Inter-Laboratory Test
Citation: AGROCHIMICA vol. 52 no. 2 p. 71-82
Publication Year: 2008
JRC N°: JRC33935
ISSN: 0002-1857
URI: http://publications.jrc.ec.europa.eu/repository/handle/JRC33935
Type: Articles in periodicals and books
Abstract: Good soil structure and high aggregate stability are crucial issues to be considered for improving soil fertility, crop production and environmental quality. Administrators and Policy makers involved in Environmental and Agriculture Policies need efficient tools for monitoring the status of cultivated soil. To face these requests and provide practical solutions, a rapid and effective test of soil status identified and quantitative information about its reliability provided. In this study, the precision of the Tiulin method for soil wet aggregate stability index (WASI) was evaluated through an inter-laboratory test, according to the validation procedure proposed by ISO 5725. Precision was expressed in terms of repeatability (sr) and reproducibility (sR) standard deviations with related limits (r and R). Six different soils, collected from three Italian agricultural areas, with different organic matter and clay contents, were chosen and six measurement replicates were carried out for each combination of soil and laboratory. The values of sr and sR, obtained after the detection of outliers according to the Grubbs (outliers in the means) and Cochran tests (outliers in the variances), ranged respectively from 0.92 to 2.93 and from 1.42 to 12.31. The corresponding r and R ranged from 2.57 to 8.22 and from 3.98 to 34.48. No significant correlations were found both between WASI and r or between WASI and R. On the contrary the relative standard deviation of repeatability was inversely correlated (R2 = 0.88, **P<0.01) with soil organic matter. The precision is within the range of other chemical and biological methods and can be considered satisfactory. The results obtained in this study have demonstrated the suitability of the Tiulin method as a standard method for monitoring soil physical quality.
JRC Directorate:Space, Security and Migration

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