EFFECTS OF TALLER WHEAT RESIDUE AFTER STRIPPER HEADER HARVEST ON WIND RUN, IRRADIANT ENERGY INTERCEPTION, AND EVAPORATION

Authors: Baumhardt, Roland; Schwartz, Robert; Todd, Richard

Submitted to: Annual Southern Conservation Tillage Conference for Sustainable Agriculture
Publication Type: Proceedings
Publication Acceptance Date: 5/24/2002
Publication Date: 6/26/2002
Citation: N/A

Interpretive Summary: Storage of precipitation in the soil is important for stable dryland crop production in the southern Great Plains. This region has high winds that dry the soil and reduce precipitation storage efficiency. Evaporation may be reduced with residues that shade the soil and reduce the wind speed near the soil surface. Combine harvesters with stripper type headers remove grain while leaving behind taller erect straw than left by conventional platform headers, which may reduce evaporation. Our objectives were: to characterize the effect of residue height after wheat (Triticum aestivum L.) harvest with stripper, SHH, or conventional sicklebar platform, PHH, headers on wind speed, intercepted solar irradiance, and evaporation. We measured wind velocity, solar irradiance at the soil surface, and evaporation in two 16-acre wheat fields after stripper header or platform header harvest. Compared with PHH wheat straw, the taller straw retained by SHH reduced mean wind velocity and potential evaporation. Measured irradiant energy at the soil surface was 12% lower in the taller straw left by the SHH compared with short straw left by the PHH. Consequently, estimated soil evaporation from SHH plots was reduced 26% compared to PHH plots during a 4-day evaluation interval. However, the differences in evaporation between the tall and short straw were very small because of the dry soil conditions during our experiment. We conclude that water conservation will be increased when using stripper type combine headers to harvest wheat because taller straw reduced wind velocity and increased interception of irradiant energy.

Technical Abstract: Storage of precipitation as soil water is critical to stable dryland crop production in the semiarid southern Great Plains. The region is characterized by high winds that promote evaporation and reduce precipitation storage efficiency. Evaporation may be reduced by residues that intercept irradiant energy and increase the aerodynamic resistance. Combine harvesters with stripper type headers remove grain while leaving behind taller erect straw than left by conventional platform headers, and; thus, potentially reduce evaporation. Our objectives were: to characterize the effect of residue height after wheat (Triticum aestivum L.) harvest with stripper, SHH, or conventional sicklebar platform, PHH, headers on wind velocity, intercepted solar irradiance, and evaporation. We measured wind velocity, solar irradiance at the soil surface, and evaporation with Bowen ratio radiation and energy balance systems in two contiguous 16-acre wheat fields after stripper header or platform header harvest. Compared with PHH wheat straw, the taller straw retained by SHH reduced mean wind velocity and reduced potential transport of water vapor (especially for evaporation from wet soil). Measured irradiant energy at the soil surface was 12% lower in the taller straw left by the SHH compared with short straw left by the PHH. Consequently, Bowen ratio estimated soil evaporation from SHH plots was reduced 26% compared to PHH plots during a 4-day evaluation interval. However, the differences in evaporation between the tall and short straw were very small because of the dry soil conditions during our experiment. We conclude that water conservation will be increased when using stripper type combine headers to harvest wheat because taller straw reduced wind velocity and increased interception of irradiant energy.