The effect of conservation tillage on runoff erosivity and soil erodibility during concentrated flow

Knapen, A. and Poesen, J. and Govers, J. and De Baetsb, S. (2008) The effect of conservation tillage on runoff erosivity and soil erodibility during concentrated flow. Hydrological Processes, 22 (10). pp. 1497-1508.

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Crop residues in conservation tillage systems are known to cause both a reduction in the erosive runoff power and an increase in the topsoil erosion resistance. In this study, the relative importance of both mechanisms in reducing soil loss by concentrated flow erosion is examined. Therefore, a method to calculate the effective flow shear stress responsible for soil detachment in the presence of a residue cover is applied. The determination of effective flow shear stress is based on the recalculation of the hydraulic radius for residue treatments. The method was tested in a laboratory flume by comparing soil detachment rates of identical pairs of soil samples that only differ in the presence or absence of crop residues. This shear stress partitioning approach and a soil detachment correction were then applied to a dataset of soil detachment measurements on undisturbed topsoil samples from a no-till field plot on a loess-derived soil, sampled during one growing season. Results indicate that only a small fraction (10% on average) of the difference in soil detachment rate between conventional and conservation tillage can be attributed to the dissipation of shear forces on the residues. The remaining decrease in soil detachment during concentrated runoff after a two-year application of conservation tillage can be explained by the increased dry bulk density and root and crop residue content in the topsoil that reduces soil erodibility. After correcting for the presence of residues, the temporal variability in soil detachment rates (Dr) during concentrated flow for a given flow shear stress (τ) for both treatments can be predicted fairly well (R2 = 0·87) from dry soil bulk density (DBD, representing consolidation effects), soil moisture content (SMC, representing antecedent rainfall conditions), the dry mass of organic material (OM, representing root growth and residue decomposition) and saturated soil shear strength σs, sat using an equation of the form:...

Item Type: Article
Additional Information: This study was supported by the Fund for Scientific Research Flanders (FWO Vlaanderen). The Belgian team of the Soil and Water Protection (SOWAP) Life project of the European Commission and the Van Acker family are thanked for enabling sampling at the two field plots of the Huldenberg field site. The authors gratefully acknowledge the assistance of Patricia Galindo Morales during the experiments.
Uncontrolled Keywords: topsoil resistance; concentrated runoff; no tillage; effective flow shear stress; shear stress partitioning; rill; ephemeral gully
Author Affiliation: Physical and Regional Geography Research Group, K. U. Leuven, GEO-Institute, Celestijnenlaan 200E, 3001 Heverlee, Belgium.
Subjects: Soil Science and Microbiology
Divisions: General
Depositing User: Mr. SanatKumar Behera
Date Deposited: 24 Dec 2013 05:08
Last Modified: 24 Dec 2013 05:08
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