[(SQ -- 12) Wind Erosion Management Considerations (Assessment
Guide)]{.mark}

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<td colspan="24"><strong>E = f (IKCLV): E = estimated avg. annual soil
loss in tons/ac/yr; f = relationships are not straight-line mathematical
calculations; I = soil erodibility index; K = soil surface roughness
factor; C = climatic factor; L = unsheltered distance; V = vegetative
cover</strong></td>
</tr>
<tr class="even">
<td rowspan="13"></td>
<td colspan="2"><h1 id="i">I</h1></td>
<td rowspan="13"></td>
<td colspan="5"><h2 id="k">K</h2></td>
<td rowspan="13"></td>
<td colspan="2"><h2 id="c">C</h2></td>
<td colspan="2"><h5 id="mo.-ewe">Mo. %EWE</h5></td>
<td rowspan="13"><h2 id="section"></h2></td>
<td colspan="3"><h2 id="l">L</h2></td>
<td rowspan="12"><h2
id="the-smaller-the-unsheltered-distance-the-lower-the-soil-erosion"><mark>The
smaller the <u>unsheltered</u> <u>distance</u>, the lower the soil
erosion</mark></h2></td>
<td rowspan="13"><h2 id="section-1"></h2></td>
<td colspan="3"><strong>V</strong></td>
<td rowspan="13"><h2 id="section-2"></h2></td>
</tr>
<tr class="odd">
<td rowspan="2"><strong>WEG</strong></td>
<td rowspan="2"><p><strong>SEI</strong></p>
<h4 id="tacyr">T/ac/yr</h4></td>
<td colspan="2"><strong>Krd</strong></td>
<td colspan="3"><strong>Krr</strong></td>
<td colspan="2" rowspan="2"><p><strong>NM</strong></p>
<p><strong>C factors</strong></p></td>
<td rowspan="11"><p><strong>Jan</strong></p>
<p><strong>Feb</strong></p>
<p><strong>Mar</strong></p>
<p><strong>Apr</strong></p>
<p><strong>May</strong></p>
<p><strong>Jun</strong></p>
<p><strong>Jul</strong></p>
<p><strong>Aug</strong></p>
<p><strong>Sep</strong></p>
<p><strong>Oct</strong></p>
<p><strong>Nov</strong></p>
<p><strong>Dec</strong></p></td>
<td rowspan="11"><p><strong>4.1</strong></p>
<p><strong>23.7</strong></p>
<p><strong>26.8</strong></p>
<p><strong>17.6</strong></p>
<p><strong>11.0</strong></p>
<p><strong>1.6</strong></p>
<p><strong>.4</strong></p>
<p><strong>.2</strong></p>
<p><strong>.9</strong></p>
<p><strong>1.3</strong></p>
<p><strong>5.0</strong></p>
<p><strong>7.6</strong></p></td>
<td rowspan="2"><p><strong>WED</strong></p>
<p><strong>Factor</strong></p></td>
<td colspan="2" rowspan="11"><blockquote>
<p><strong>Multiply the <u>WED factor</u> times the Width of the
Field</strong></p>
<p><strong>to determine the Unsheltered Distance (L) in
feet.</strong></p>
</blockquote></td>
<td colspan="3" rowspan="2"><blockquote>
<p><strong>Lbs/acre of residues or growing crops</strong></p>
</blockquote></td>
</tr>
<tr class="even">
<td colspan="5"><h4 id="k-krd-x-krr">K = Krd x Krr</h4></td>
</tr>
<tr class="odd">
<td><strong>1</strong></td>
<td><strong>220</strong></td>
<td rowspan="9"><p><strong>1</strong></p>
<p><strong>.9</strong></p>
<p><strong>.8</strong></p>
<p><strong>.7</strong></p>
<p><strong>.6</strong></p>
<p><strong>.5</strong></p>
<p><strong>.4</strong></p></td>
<td rowspan="9"><blockquote>
<p><strong><mark>Lower <u>Krd</u> factor = lower soil
erosion</mark></strong></p>
</blockquote></td>
<td rowspan="9"><p><strong>1</strong></p>
<p><strong>.9</strong></p>
<p><strong>.8</strong></p>
<p><strong>.7</strong></p>
<p><strong>.6</strong></p>
<p><strong>.5</strong></p>
<p><strong>.4</strong></p></td>
<td colspan="2" rowspan="9"><blockquote>
<p><strong><mark>Lower <u>Krr</u> factor = lower soil
erosion</mark></strong></p>
</blockquote></td>
<td rowspan="9"><p><strong>30</strong></p>
<p><strong>50</strong></p>
<p><strong>80</strong></p>
<p><strong>100</strong></p>
<p><strong>120</strong></p>
<p><strong>150</strong></p></td>
<td rowspan="9"><blockquote>
<p><strong><mark>Lower C factor = lower soil erosion</mark></strong></p>
</blockquote></td>
<td rowspan="9"><p><strong>1.00</strong></p>
<p><strong>3.00</strong></p>
<p><strong>5.00</strong></p>
<p><strong>7.00</strong></p>
<p><strong>9.00</strong></p>
<p><strong>11.00</strong></p>
<p><strong>13.00</strong></p></td>
<td rowspan="9"><blockquote>
<p><strong>Refer to the Small Grain equivalents (SGe) curves found in
the NRCS National Agronomy Manual (NAM), Part 502, Figures a-1 through
d-8.</strong></p>
</blockquote></td>
<td rowspan="9"><blockquote>
<p><strong><mark>Higher residue = lower soil erosion</mark></strong></p>
</blockquote></td>
<td rowspan="9"><blockquote>
<p><strong>The SGe expresses the effectiveness of residue</strong></p>
</blockquote>
<p><strong>or growing crops in resisting wind erosion.</strong></p></td>
</tr>
<tr class="even">
<td><strong>2</strong></td>
<td><strong>104</strong></td>
</tr>
<tr class="odd">
<td><strong>3</strong></td>
<td><strong>56</strong></td>
</tr>
<tr class="even">
<td><strong>4</strong></td>
<td><strong>56</strong></td>
</tr>
<tr class="odd">
<td><strong>4L</strong></td>
<td><strong>56</strong></td>
</tr>
<tr class="even">
<td><strong>5</strong></td>
<td><strong>38</strong></td>
</tr>
<tr class="odd">
<td><strong>6</strong></td>
<td><strong>21</strong></td>
</tr>
<tr class="even">
<td><strong>7</strong></td>
<td><strong>21</strong></td>
</tr>
<tr class="odd">
<td><strong>8</strong></td>
<td><strong>0</strong></td>
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<td colspan="8"><ul>
<li><p><strong><mark><u>WEG</u></mark> = Wind Erodibility
Group</strong></p></li>
<li><p><strong><mark><u>SEI</u></mark> = Soil Erodibility Index (I) for
irrigated soils</strong></p></li>
<li><p><strong><mark><u>Krd</u></mark> = Soil Ridge Roughness factor (is
a function of Ridge height &amp; Spacing, Angle of deviation &amp;
SEI)</strong></p></li>
<li><p><strong><mark><u>Krr</u></mark> = Random Roughness (rr) factor
(Krr is a function of Cloddiness, as created by tillage &amp;
SEI)</strong></p></li>
<li><p><strong><mark><u>C</u></mark> is a function of windspeed &amp;
surface soil moisture</strong></p></li>
<li><p><strong><mark><u>% EWE</u></mark> = % Erosive Wind Energy (values
are for Las Cruces, NM)</strong></p></li>
</ul></td>
<td colspan="9"><ul>
<li><p><strong><mark><u>WED</u></mark> = Wind Erosion Direction factor
(Reference: Tables 502-8A thru 502-8E of the NRCS NAM). WED factors are
a function of field length/width ratio, wind preponderance and angle of
deviation.</strong></p></li>
<li><p><strong><mark><u>V</u></mark> factor relates the kind, amount
&amp; orientation of vegetative material to its equivalent in lbs/ac of
small grain residue in reference condition Small Grain Equivalent
(SGe)</strong></p></li>
</ul></td>
<td colspan="7"><p><mark><u>e.g. calculation:</u></mark> A fine textured
soil was irrigated 3x during 45 days. 12% of the annual EWE occurs
during this period. Therefore: Texture Wetness Factor (TWF) = 3; No. of
irrigations during period = 3; Nonerodible Wet Days = 3 x 3 = 9;</p>
<p><strong>Irrigation Factor (IF) = (45 – 9) ÷ 45 = .80; Adjusted EWE =
(.80) (12%) = 9.6%</strong></p>
<p><strong><mark><u>Note:</u> angle of deviation is 0<sup>0</sup>, when
wind is perpendicular to the row</mark></strong></p>
<p><strong>Rudy Garcia 2008</strong></p></td>
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[[NOTE:]{.underline} NRCS will be using WEPS (Wind Erosion Prediction
System) to make wind erosion assessments]{.mark}