WIND EROSION EQUATION Recent Changes (NAM) USDA-NRCS

Wind Erosion continues to be a serious problem in the semiarid and arid regions of the US.

The Good Old Days

The Good Old Days cont.

WEQ Changes made! l WEQ has been updated to account for irrigation effects, random roughness and I Factor adjustments. l WEQ changes are outlined in the new edition of the National Agronomy Manual.

Introduction WEQ Excel Spreadsheet l Cover NAM changes l Changes to Ridge Roughness l Addition of Random Roughness l Quick intro to the Excel spreadsheet l Demo how to edit and make changes l Answer Questions

Spreadsheet History l Began as a spreadsheet by Tom Keep l Then Circular 2, NAM amendment Sept. 12, 1997 was incorporated l SGe calculations added, 1998 l Krd-Ridge Roughness formulas added in 1998

Circular 2 Changes  I Adjustment for Irrigation -Above 180 no adjustment -180 or less, reduce one I class  IF – ‘Irr. Factor’ reduces Erosive Wind Energy (EWE) for mgt period  Random Roughness (Krr) combined with Ridge Roughness (Krd)

ADJUSTMENTS TO “I” l Irrigation adjustment (IF) -adjustment applies to all soils

EWE IRRIGATION ADJUSTMENT l Effects of wet soil is accounted for by adjusting the EWE for the mgt period l Bare wet soil remains non-erodible wet: – 1 day for coarse textured soils – 2 days for medium textured soils – 3 days for fine textured soils l See sheet “WEG tab” for table

ADJUSTMENTS TO “I” - IRRIGATION

“Krr” RANDOM ROUGHNESS FACTOR l Soil cloddiness raises the threshold wind speed at which erosion begins l Provides sheltered area among clods where moving soil can be trapped l Spreadsheet reduces RR (clodsize) by one half after 15 days.

“Krr” RANDOM ROUGHNESS FACTOR l Non-oriented surface roughness – Cloddiness l Usually created by tillage implements l Values represented as standard deviation, in inches, of roughness heights l Use Random Roughness-Guidance sheet l Roughness assigned to each tillage implement (ideal conditions)

Random Roughness - Krr

Ridge Roughness- Krd l Revised NAM has new tables l Based on I values and Preponderance l Low Preponderance values indicate less of the erosive wind is from the prevailing wind direction. l Higher Krd values indicate that ridges are less effective l Krd can be lower than 0.5 now

Irrigation Input Requirements l Enter the number of Irrigations, including pre-plant and post harvest irrigation l “Non-erodible wet days” will be calculated based on soil texture (WEG) l Drip irrigation poses a problem. Need to estimate the % of surface that is non- erodible wet

Circle Irrigation Day 1-24 hrs Day 2-24 hrs Day 3-24 hrs Day 4-24 hrs It takes this system 96 hours to make one complete circle. For WEQ this is one irrigation. The soil texture determines the number of non- erodible wet days (1,2,or 3) per irrigation

l With the WEQ Speadsheet, field width is the distance across the short side of the field or average short side of a polygon. Field Width

Field Width vs Unsheltered Distance Field Width

Field Width vs Unsheltered Distance l The Excel Spreadsheet model will determine L using the length/width ratio of the field, the angle of deviation, wind preponderance and the resulting wind erosion direction factor.

Computer Requirements l Need 486 minimum. l 586 is better l Windows 95, 98, or NT l Excel version 7.0 l 16 mg of RAM or better l File name WEQvs8.01.xls

INSTR sheet l Wind Erosion Model Worksheet Legend -Definitions l Describes input data and column headings l New-Krd, Krr, IF, No. of Irr, and TWF Read this sheet first.

Res WKS sheet Required Inputs l Operation Dates l Crop Names l Operations l Percent Flat Residue l Number of irrigation per mgt period l Yield adjustment l Prod., Farm, Tract, Field, C, I, Field Width, LW ratio, Tillage Dir, Field Dir, Irr (y/n)

Calc sheet l Detailed calculations by Mgt Period l Note Krd, Krr, and IF factors added here l No inputs needed or allowed

Data Tables l Crop table -Need to maintain crop data; residue produced and green growth l Tillage table -Residue reduction -Random roughness assigned to tillage

Data Tables cont. l Climate data, the wind direction, EWE, and Preponderance must be added for climate stations in your state.

Summary l If Users have a basic understanding of the EXCEL spreadsheet, they can use this model. l State Agronomist should become familiar with the wind data (climate file), crop data, and operation (tillage) files before beginning use in a new state.

Limitations l We can not change tillage direction in each mgt period. l Need to create templates and save for later use. l It does not allow for crusting (no I factor adjustment for a period of crusting).

Limitations l Growth curve data is limited l Do not have SGe curves for all crops both green and dry

Where to get more information l Call State Agronomists for assistance: l State Agronomists can call: Mike Sporcic, or,

Where to get more information l Gary Tibke– (785) l Lorenz Sutherland--(719) l Websites for WEQ or We’re Done

Questions & Short Demo END

The End