Influence of Soil Properties on the Statistical Characterization of Dry Aggregate Strength
1995
Perfect, E. | Kay, B. D. | da Silva, A. P.
Dry aggregate strength measurements, important in tillage and erosion studies, are often analyzed statistically using the Weibull model. The parameters of this model, α and β, characterize the absolute strength and the spread of strengths, respectively. Information is lacking on the influence of soil properties on values of α and β. We measured dry aggregate strength as the specific rupture energy (E in J g⁻¹) of 40 aggregates in two size classes (4–8 and 8–16 mm) from 36 locations along a 500‐m transect across four soil types with a wide range of physical and chemical properties (e.g., 8.0–72.6% sand content). Estimates of α and β were obtained by fitting Weibull's model to these data using nonlinear regression. The α and β values were lognormally and normally distributed, respectively. The mean log(α) was ‐2.4 and the mean β was 1.3. Multiple regression analysis was used to relate log(α) and β to soil properties. The resulting regression equations explained 93% of the variation in log(α) and 60% of the variation in β. The log(α) increased with decreasing aggregate size and sand content and increasing organic matter content. The β increased (indicating a narrower range of strength values) with decreasing log(α) and aggregate size. The regression equations were validated by predicting the cumulative relative frequency distribution of E for aggregates from a different site where independent measurements of E were available for comparison. A good agreement (R² ≥ 0.91) was obtained between predicted and observed values of E.
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