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Aerodynamic Characteristics of Standing Corn Stubble
Author(s) -
Sauer Thomas J.,
Hatfield Jerry L.,
Prueger John H.
Publication year - 1996
Publication title -
agronomy journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 131
eISSN - 1435-0645
pISSN - 0002-1962
DOI - 10.2134/agronj1996.00021962008800050009x
Subject(s) - wind speed , crop residue , tillage , environmental science , wind tunnel , turbulence , aerodynamics , roughness length , atmospheric sciences , agronomy , mathematics , soil science , meteorology , wind profile power law , physics , mechanics , ecology , biology , agriculture
Maintenance of crop residues on the soil surface is promoted as a management practice for reducing soil erosion by wind and water. Crop residue on the soil surface, however, also influences turbulent exchange processes that affect surface water and energy balances. At present, there are very limited data on the aerodynamic properties of residue‐covered surfaces. The objective of this research was to derive estimates of the aerodynamic properties (momentum roughness length z 0 , zero‐plane displacement d , and drag coefficient C d ) of fields with standing corn ( Zea mays L.) stubble. Wind speed and air temperature measurements were made at six heights above two no‐tillage fields near Ames, IA, in the spring and fall of 1994 and in the spring of 1995. Both sites had standing corn stubble approximately 0.3 m tall at a density of greater than 60 000 stalks ha −1 and nearly 95% residue cover. An iterative, least‐squares linear regression technique was applied to wind profiles obtained under neutral atmospheric conditions to determine z 0 , d , and the friction velocity ( u .). Mean values of z 0 and d for each of the three measurement periods varied from 11.8 to 24.3 and 119 to 169 mm, respectively. The ratios z 0 / h s and d / h s , where h s is the mean stubble height, averaged 0.058 and 0.53, respectively, for all profiles. The magnitude of zo and d and their weak dependence on wind speed are consistent with turbulent flow over a surface with sparse, rigid roughness elements. The z 0 and C d were higher for the fall measurement period, suggesting that the loose, fresh residue presented a comparatively rough surface that was then smoothed by weathering and compaction beneath snow.