Fractal Characterization of Soil Aggregation and Fragmentation as Influenced by Tillage Treatment
1997
Perfect, E. | Blevins, R. L.
Parameters are needed to quantify tillage-induced changes in soil structure. Our objective was to see if fractal parameters from ped mass- and number-size relations could be applied to quantify such changes. Soil from long-term conventional (moldboard plow, MP, plus two passes with a disk harrow, DH) and no-till (NT) plots on a Maury silt loam (fine, mixed, mesic Typic Paleudalf) was air dried and sieved into six size classes ranging from 0.5–1 to 16–31.5 mm. The mass percentage and weight of 100 peds in each size class were used to calculate the mean mass per ped and number of peds as a function of scale. Fractal equations were then fitted to both data sets (R² always ≥ 0.99). The resulting parameter estimates were Dₘ (mass fractal dimension) and kₘ (mass of an aggregate of unit length) for the mass-size relation, and Dₜ (fragmentation fractal dimension) and kf (number of fragments of unit length) for the number-size distribution. Significant tillage effects were observed for Dₘ, Df, and kf. The Dₘ increased from 2.88 for NT to ≥ 2.94 for MP and DH, suggesting differential compaction of large aggregates by plowing and disking. The Df was always less than the Dₘ, as predicted by theory. Soil fragmentation was least for NT (Df = 2.02) and greatest for MP (Df = 2.55); for DH, the Df = 2.15 suggesting that disking broke up large fragments and/or coalesced small fragments following plowing. The kf, which was shown to be nonlinearly related to the Df, was least for MP and greatest for NT. Similar studies on other soils are needed to test the general applicability of these fractal relations to soil structure.
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