WIND EROSION EQUATIONWIND EROSION EQUATIONRecent Changes (NAM)Recent Changes (NAM)

USDA-NRCSUSDA-NRCS

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

The Good Old DaysThe Good Old Days

The Good Old Days The Good Old Days cont.cont.

WEQ Changes made!WEQ Changes made!

WEQ has been updated to account for irrigation effects, random roughness and I Factor adjustments.

WEQ changes are outlined in the new edition of the National Agronomy Manual.

Introduction WEQ Excel Introduction WEQ Excel SpreadsheetSpreadsheet

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

Spreadsheet HistorySpreadsheet History

Began as a spreadsheet by Tom Keep Then Circular 2, NAM amendment Sept.

12, 1997 was incorporated SGe calculations added, 1998 Krd-Ridge Roughness formulas added in

1998

Circular 2 ChangesCircular 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”ADJUSTMENTS TO “I”

Irrigation adjustment (IF)

-adjustment applies to all soils

EWE IRRIGATION EWE IRRIGATION ADJUSTMENTADJUSTMENT

Effects of wet soil is accounted for by adjusting the EWE for the mgt period

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

See sheet “WEG tab” for table

ADJUSTMENTS TO “I” - ADJUSTMENTS TO “I” - IRRIGATIONIRRIGATION

Wind Erodibility Groups and Soil Erodibility Index

Soil EWE Soil Erodibility Texture Wind Erodibility Index (I) for Wetness Predominant Soil Texture Erodibility Index (I) Irrig. Soils Factor Class of Surface Layer Group (WEG) (T/Ac/Yr) (T/Ac/Yr) 1 Very fine sand, fine sand, sand 1 310 310 or coarse sand. 250 250 220 220 180 160 160 134 1 Loamy very fine sand, loamy fine 2 134 104 sand, loamy sand, loamy coarse sand, or sapric organic soil materials. 1 Very fine sandy loam, fine sandy loam, 3 86 56 sandy loam, or coarse sandy loam. 3 Clay, silty clay, noncalcareous clay loam, 4 86 56 or silty clay loam with more than 35% clay. 2 Calcareous loam and silt loam, or calcar- 4L 86 56 eous clay loam and silty clay loam. 2 Noncalcareous loam and silt loam with 5 56 38 less than 20% clay, or sandy clay loam, sandy clay, and hemic organic soil materials. 2 Noncalcareous loam and silt loam with 6 48 21 more than 20% clay, or noncalcareous clay loam with less than 35% clay. 2 Silt, noncalcareous silty clay loam with 7 38 21 less than 35% clay and fibric organic soil material.

““Krr” RANDOM Krr” RANDOM ROUGHNESS FACTORROUGHNESS FACTOR

Soil cloddiness raises the threshold wind speed at which erosion begins

Provides sheltered area among clods where moving soil can be trapped

Spreadsheet reduces RR (clodsize) by one half after 15 days.

““Krr” RANDOM Krr” RANDOM ROUGHNESS FACTORROUGHNESS FACTOR

Non-oriented surface roughness– Cloddiness

Usually created by tillage implements Values represented as standard

deviation, in inches, of roughness heights Use Random Roughness-Guidance sheet Roughness assigned to each tillage

implement (ideal conditions)

Random Roughness - KrrRandom Roughness - Krr

Ridge Roughness- KrdRidge Roughness- Krd

Revised NAM has new tables Based on I values and Preponderance Low Preponderance values indicate less

of the erosive wind is from the prevailing wind direction.

Higher Krd values indicate that ridges are less effective

Krd can be lower than 0.5 now

Irrigation Input Irrigation Input RequirementsRequirements

Enter the number of Irrigations, including pre-plant and post harvest irrigation

“Non-erodible wet days” will be calculated based on soil texture (WEG)

Drip irrigation poses a problem. Need to estimate the % of surface that is non-erodible wet

Circle IrrigationCircle Irrigation

Day 1-24 hrsDay 1-24 hrsDay 2-24 hrsDay 2-24 hrs

Day 3-24 hrsDay 3-24 hrs Day 4-24 hrsDay 4-24 hrs

It takes this system 96 hours to make one complete circle. For WEQ this is one irrigation.

The soil texture The soil texture determines the determines the number of non-number of non-erodible wet erodible wet days (1,2,or 3) days (1,2,or 3) per irrigationper irrigation

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

Field WidthField Width

Field Width vs Field Width vs Unsheltered DistanceUnsheltered Distance

89

“L” - UNSHELTERED DISTANCE

Stable Area

L

isolated field

PREVAILING WINDEROSION DIRECTION

FieldWidth

Field Width vs Field Width vs Unsheltered DistanceUnsheltered Distance

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 RequirementsComputer Requirements

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

INSTRINSTR sheet sheet

Wind Erosion Model Worksheet Legend

-Definitions Describes input data and column

headings New-Krd, Krr, IF, No. of Irr, and TWF

Read this sheet first.Read this sheet first.

Res Res WKS sheetWKS sheetRequired InputsRequired Inputs

Operation Dates Crop Names Operations Percent Flat Residue Number of irrigation per mgt period Yield adjustment Prod., Farm, Tract, Field, C, I, Field Width,

LW ratio, Tillage Dir, Field Dir, Irr (y/n)

Calc sheetCalc sheet

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

Data TablesData Tables

Crop table

-Need to maintain crop data;

residue produced and green growth Tillage table

-Residue reduction

-Random roughness assigned to tillage

Data Tables cont.Data Tables cont.

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

SummarySummary If Users have a basic understanding of

the EXCEL spreadsheet, they can use this model.

State Agronomist should become familiar with the wind data (climate file), crop data, and operation (tillage) files before beginning use in a new state.

LimitationsLimitations

We can not change tillage direction in each mgt period.

Need to create templates and save for later use.

It does not allow for crusting (no I factor adjustment for a period of crusting).

LimitationsLimitations

Growth curve data is limited Do not have SGe curves for all crops both

green and dry

Where to get more Where to get more informationinformation

Call State Agronomists for assistance: State Agronomists can call:

Mike Sporcic, michael.sporcic@nm.usda.gov , 505-761-442

or,

Where to get more Where to get more informationinformation

Gary Tibke– (785)537-5541

tibke@weru.ksu.edu Lorenz Sutherland--(719)384-5408

lorenz.sutherland@co.usda.gov Websites for WEQ

www.nm.nrcs.usda.gov/techserv or www.weru.ksu.edu/nrcs

We’re DoneWe’re Done

Questions & Short Demo Questions & Short Demo ENDEND

The EndThe End