**[(WQ -- 4) Irrigation Water Salinity & Sodium Adsorption Ratio (SAR)
Assessment Guide]{.mark}**

<table>
<colgroup>
<col style="width: 3%" />
<col style="width: 22%" />
<col style="width: 5%" />
<col style="width: 5%" />
<col style="width: 5%" />
<col style="width: 0%" />
<col style="width: 5%" />
<col style="width: 3%" />
<col style="width: 6%" />
<col style="width: 10%" />
<col style="width: 6%" />
<col style="width: 5%" />
<col style="width: 5%" />
<col style="width: 1%" />
<col style="width: 4%" />
<col style="width: 5%" />
</colgroup>
<tbody>
<tr class="odd">
<td colspan="16"><strong>Irrigation Water Lab Analysis for Soluble Salts
and SAR (mg/l = milligrams/liter; meq/l =
milliequivalents/liter)</strong></td>
</tr>
<tr class="even">
<td rowspan="2"></td>
<td rowspan="2"><p><strong>Major Cations</strong></p>
<p><strong>(ions with a positive charge)</strong></p></td>
<td colspan="2"><strong>example</strong></td>
<td colspan="3"><strong>Enter Lab Results</strong></td>
<td rowspan="4"></td>
<td colspan="3" rowspan="2"><p><strong>Major Anions</strong></p>
<p><strong>(ions with a negative charge)</strong></p></td>
<td colspan="2"><strong>example</strong></td>
<td colspan="3"><p><strong>Enter Lab</strong></p>
<p><strong>Results</strong></p></td>
</tr>
<tr class="odd">
<td><strong>mg/l</strong></td>
<td><strong>meq/l</strong></td>
<td><strong>mg/l</strong></td>
<td colspan="2"><strong>meq/l</strong></td>
<td><strong>mg/l</strong></td>
<td><strong>meq/l</strong></td>
<td colspan="2"><strong>mg/l</strong></td>
<td><strong>meq/l</strong></td>
</tr>
<tr class="even">
<td rowspan="2"><blockquote>
<p><strong>Hardness</strong></p>
</blockquote></td>
<td><p>Calcium (Ca<sup>++</sup>)</p>
<p><strong>20.04 mg/meq</strong></p></td>
<td>80</td>
<td>4</td>
<td></td>
<td colspan="2"></td>
<td colspan="3"><p>Chloride (Cl<sup>-</sup>)</p>
<p><strong>35.46 mg/meq</strong></p></td>
<td>92</td>
<td>2.6</td>
<td colspan="2"></td>
<td></td>
</tr>
<tr class="odd">
<td><p>Magnesium (Mg<sup>++</sup>)</p>
<p><strong>12.16 mg/meq</strong></p></td>
<td>14</td>
<td>1.2</td>
<td></td>
<td colspan="2"></td>
<td colspan="3"><p>Sulfate (SO4<sup>--</sup>)</p>
<p><strong>48.03 mg/meq</strong></p></td>
<td>192</td>
<td>4</td>
<td colspan="2"></td>
<td></td>
</tr>
<tr class="even">
<td rowspan="3"></td>
<td><p>Sodium (Na<sup>+</sup>)</p>
<p><strong>22.99 mg/meq</strong></p></td>
<td>115</td>
<td>5</td>
<td></td>
<td colspan="2"></td>
<td rowspan="2"><blockquote>
<p><strong>Alkalinity</strong></p>
</blockquote></td>
<td colspan="3"><p>Bicarbonate (HCO<sub>3</sub><sup>-</sup>)</p>
<p><strong>61.02 mg/meq</strong></p></td>
<td>183</td>
<td>3</td>
<td colspan="2"></td>
<td></td>
</tr>
<tr class="odd">
<td><p>Potassium (K<sup>+</sup>)</p>
<p><strong>39.10 mg/meq</strong></p></td>
<td>8</td>
<td>0.2</td>
<td></td>
<td colspan="2"></td>
<td colspan="3"><p>Carbonate (CO<sub>3</sub><sup>--</sup>)</p>
<p><strong>30.01 mg/meq</strong></p></td>
<td>6</td>
<td>0.2</td>
<td colspan="2"></td>
<td></td>
</tr>
<tr class="even">
<td>Sum of Total Cations:</td>
<td><strong>217</strong></td>
<td><strong>10.4</strong></td>
<td></td>
<td colspan="2"></td>
<td></td>
<td colspan="3">Sum of Total Anions:</td>
<td><strong>473</strong></td>
<td><strong>9.8</strong></td>
<td colspan="2"></td>
<td></td>
</tr>
<tr class="odd">
<td colspan="16"><p><strong>Total Dissolved Solids (i.e., Soluble Salts)
is: 217 mg/l + 473 mg/l = 690 mg/l (or 690 ppm). 0.23 x TDS (ppm) = lbs.
of salts/ac-in</strong></p>
<p><strong>690 mg/l ÷ 640 ≈ ECiw of 1.1 dS/m (i.e., Electrical
Conductivity of Irrigation Water in decisiemens/meter)</strong></p></td>
</tr>
<tr class="even">
<td colspan="16"><strong>Irrigation Water Salinity
Assessment</strong></td>
</tr>
<tr class="odd">
<td colspan="9" rowspan="3"><p><strong>Salinity (Soluble
Salts):</strong> affects crop water availability</p>
<p><u>Note:</u> Be sure to compare the Irrigation Salinity (ECiw) with
the Soil Test (ECe), in order to evaluate the potential yield reduction
of your crop (i.e., Refer to a Crop Threshold Soil Salinity (ECe(ct))
Table)</p></td>
<td colspan="7"><strong>Degree of Restriction on Use – ECiw
(dS/m)</strong></td>
</tr>
<tr class="even">
<td><strong>None</strong></td>
<td colspan="4"><strong>Slight to Moderate</strong></td>
<td colspan="2"><strong>Severe</strong></td>
</tr>
<tr class="odd">
<td><strong>&lt; 0.7</strong></td>
<td colspan="4"><strong>0.7 – 3.0</strong></td>
<td colspan="2"><strong>&gt; 3.0</strong></td>
</tr>
<tr class="even">
<td colspan="16"><strong>Irrigation Water Quality and its potential
effects on Infiltration</strong></td>
</tr>
<tr class="odd">
<td colspan="6" rowspan="7"><p>The amount of
<strong><u>Sodium</u></strong> and <strong><u>soluble salts</u></strong>
in the Irrigation Water affects the rate of water infiltration into the
soil. This is evaluated using the <strong>SAR</strong> (<strong>Sodium
Adsorption Ratio</strong>) and Electrical Conductivity of the Irrigation
Water <strong>(ECiw in dS/m)</strong>.</p>
<p><strong>Use meq/l for calculating the SAR</strong></p>
<p><strong>SAR = Na/√(Ca + Mg)/2</strong></p></td>
<td colspan="3" rowspan="2"><strong>SAR</strong></td>
<td colspan="7"><strong>Degree of Restriction on Use – ECiw
(dS/m)</strong></td>
</tr>
<tr class="even">
<td><strong>None</strong></td>
<td colspan="4"><strong>Slight to Moderate</strong></td>
<td colspan="2"><strong>Severe</strong></td>
</tr>
<tr class="odd">
<td colspan="3"><strong>0 – 3</strong></td>
<td><strong>&gt; 0.7</strong></td>
<td colspan="4"><strong>0.7 – 0.2</strong></td>
<td colspan="2"><strong>&lt; 0.2</strong></td>
</tr>
<tr class="even">
<td colspan="3"><strong>3 – 6</strong></td>
<td><strong>&gt; 1.2</strong></td>
<td colspan="4"><strong>1.2 – 0.3</strong></td>
<td colspan="2"><strong>&lt; 0.3</strong></td>
</tr>
<tr class="odd">
<td colspan="3"><strong>6 – 12</strong></td>
<td><strong>&gt; 1.9</strong></td>
<td colspan="4"><strong>1.9 – 0.5</strong></td>
<td colspan="2"><strong>&lt; 0.5</strong></td>
</tr>
<tr class="even">
<td colspan="3"><strong>12 – 20</strong></td>
<td><strong>&gt; 2.9</strong></td>
<td colspan="4"><strong>2.9 – 1.3</strong></td>
<td colspan="2"><strong>&lt; 1.3</strong></td>
</tr>
<tr class="odd">
<td colspan="3"><strong>20 - 40</strong></td>
<td><strong>&gt; 5.0</strong></td>
<td colspan="4"><strong>5.0 – 2.9</strong></td>
<td colspan="2"><strong>&lt; 2.9</strong></td>
</tr>
</tbody>
</table>

**Rudy Garcia 2008**