ARS | Publication request: USE OF THE CHAIN SET FOR SCALE-SENSITIVE EROSION-RELEVANT MEASUREMENT OF SOIL SURFACE ROUGHNESS

Submitted to: Agronomy Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: October 31, 1999
Publication Date: N/A

Technical Abstract: Foreshortening of a surface-laid chain provides practical measurement of soil roughness. A set of chains with link length of members in geometric progression will act as a nested set of scale filters to provide scale- sensitive measurement and overcome scale-indeterminacy inherent in single chain use. Measurements were made in 1-m2 areas on 2 soils under 4 tillages sbefore and after erosion using a 6-chain set made from roller chain welded to link lengths of 0.5, 1.0, 1.9, 3.8, 7.6, and 15 cm. Laser scanner- measured elevations were analyzed as a random roughness index (SD, corrected standard deviation) and a fraction sheltered from (wind erosion) abrasion index (FS). Scanner-derived indices were regressed against chain roughness percent (C = 100*(1 - L2/L1): L2, horizontal span; L1, chain length) differences (N = 30): SD = 1.23 + 1.53*(C15) + 1.26*(C3.8 - C15) + 0.51*(C1.0 - C3.8) + 0.42*(C0.5 - C1.0), R2 = 0.88; FS = 3.76 + 0.78*(C15) + 1.03*(C3.8 - C15) + 1.45*(C1.0 -C3.8) + 3.36*(C0.5 - C1.0), R2 = 0.91. Partial regression coefficients indicate (a) preferential dependence of the SD index on larger-scale roughness elements (RE's), showing the inefficiency and error in using this index, and (b) the chain set's ability to differentiate scales and reveal the dependence of the FS erosion-process index upon inclusion of smaller-scale RE's.