2012 Annual Report
a) Complete modifications to the portable wind tunnel for the field and laboratory experiments. b) Instrument portable wind tunnel to obtain desired wind speed threshold data for blowing flat residue. c) Conduct field wind tunnel experiments under laboratory conditions and on after-harvest winter wheat field sites in the Manhattan, KS area. d) Conduct field wind tunnel experiments under laboratory conditions and on after-harvest field sites for at least two additional crop residues (soybeans and corn or grain sorghum) in the Manhattan, KS area. e) Analyze the field data to form functional relationships between surface conditions (amount of anchored standing residue existing) and the threshold wind speeds measured vs. the quantity of stems and leaves (measured separately) that left the experimental sites (wind tunnel test plots). f) Develop the functional relationships between surface conditions and threshold wind velocities vs. lost mass of loose residue stems and leaves considered "blowing residue". g) Incorporate functional relationships into code to be implemented within WEPS.
Progress milestones and estimated completion dates: 1) Wheat (moderately tough residue class) a) Initial (exploratory) Laboratory Wind Tunnel Study Jul 1, 2012 b) Field Wind Tunnel Study – July 14, 2012 Aug 1, 2012 c) Extended Laboratory Wind Tunnel Study Sep 1, 2012 2) Soybeans (fragile residue class) a) Initial (exploratory) Laboratory Wind Tunnel Study Oct 1, 2012 b) Field Wind Tunnel Study Nov 1, 2012 c) Extended Laboratory Wind Tunnel Study Jan 1, 2013 3) Corn/Grain Sorghum (tough residue class) a) Initial (exploratory) Laboratory Wind Tunnel Study Oct 1, 2012 b) Field Wind Tunnel Study Nov 1, 2012 c) Extended Laboratory Wind Tunnel Study Jan 1, 2013 4) Data analysis and algorithm development Apr 1, 2013 5) Incorporation of algorithm into WEPS Jun 1, 2013
NRCS has witnessed many fields that have had standing residue mowed down to a height where high winds have either blown residue from the field or re-distributed it within the field, and wind erosion has occurred, even though there was sufficient residue that would normally have protected the field. NRCS realized that WEPS (Wind Erosion Prediction System) did not reflect this situation where high winds would cause the residue to either be re-distributed and/or blow off of a field, making it much more susceptible to wind erosion. Since there were no research data available on this topic, NRCS requested that suitable research be conducted to determine the conditions that this occurs and implement this phenomena within the WEPS model based upon this research. As part of this project, modifications to a portable wind tunnel have been completed for the field and laboratory experiments. Instrumentation for the portable wind tunnel has been obtained to measure desired wind speed threshold data for blowing flat residue within the tunnel. Replicated field wind tunnel experiments have also been conducted under two standing residue heights (mowed to two heights) in a harvested wheat field near Manhattan, KS. The mulched (mowed) residue was sampled to determine the fraction of stem length ranges which existed in the field. Preparations are under way for a series of laboratory wind tunnel experiments to be conducted. Specific conditions to be studied are the areal density (population) of standing stems within a row, the height of the standing stems and a range of wind speeds that exceed the static threshold friction velocity for the given conditions. The “trapping capacity” of the standing stems in the tunnel will also be determined for each wind speed measurements are taken. When the data has been fully collected and analyzed, the results will be incorporated into the WEPS model, allowing the changed surface residue conditions to be simulated when wind speeds exceed the threshold for retaining the flat residue on the surface. When fully implemented within WEPS, NRCS will be able to provide information to farmers on what minimum height their standing residue can be safely mowed and still provide adequate protection from wind erosion.