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United States Department of Agriculture

Agricultural Research Service

Title: Mechanical Integrating and Scaling Devices for Measurement of the Roughnesscomponents of Soil Erodibility

Authors
item Merrill, Stephen
item Huang, Chi Hua
item Zobeck, Teddy
item Tanaka, Donald

Submitted to: International Soil Conservation Organization Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: May 23, 1999
Publication Date: N/A

Technical Abstract: Standing and prostrate crop residues act together with soil surface microtopography to determine the roughness component of soil erodibility. Saleh has introduced the chain method to soil erosion research. The foreshortening of a roller chain laid upon the soil surface integrates the degree of soil roughness over the length of the chain.**A single, very find dchain could exhibit scale indeterminacy by reporting a similar roughness value for both a surface with many small roughness elements (RE's) and one with a lesser number of large RE's. Merrill has shown through a computer simulation study that scale indeterminancy can be overcome by use of a set of chains in which the linkage length of each chain is part of an approximate geometric progression. It was also concluded from this study that the chain set would give information about the "fractal character" of surface roughness. Fractal character is defined as the size distribution of fRE's at lesser scale than the upper dominating size scale of RE's. Thus, the chain set is a mechanical integrating and scaling device.**We have compared chain set measurements with datasets produced with a laser micro- topographic scanner. Chains in our set were from ANSI standard roller stock 92 cm in length with linkage lengths created by spot welding to be 0.48, 0.95, 1.91, 3.81, 7.62, 15.24, and 30.48 cm. Both randomly rough soil surfaces created in the lab and tillage-disturbed surfaces in the field have been comparatively measured. Two wind erosion-relevant indices were calculated from laser scanner datasets, percent of surface sheltered from abrasion and elevation standard deviation index. From measurements on randomly rough soil, it was found that chain set roughness parameters correlated well with percent of surface sheltered from abrasion.

Last Modified: 4/15/2014
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