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  <br />9  <br />  <br />  <br />6.3 Material Damage Assessment <br />There are two fields where a material damage assessment was warranted as shown on Table 4. <br />On Cox field 11, the irrigation water from LGSC water exhibits 1.72 dS/m which exceeds the <br />field salinity threshold, calculated to be 1.63 dS/m. On Proctor field 6, the irrigation water from <br />LGSC water exhibits 1.72 dS/m which exceeds the field salinity threshold, calculated to be 1.71 <br />dS/m. Both of these fields are dominated by the moderately sensitive alfalfa. <br />The formula "Y = 100 - Bw (ECw - Aw)" developed by Maas and Hoffman (1977) modified for <br />irrigation water would be used to predict crop yield loss, where: <br />Y = Relative Yield <br />Aw = Salinity Threshold (irrigation water) <br />ECw = Predicted Conductivity (irrigation water) <br />Bw = Percent Yield Decrease Per Unit Increase in Conductivity of Irrigation Water <br />The equation is based on the assumption that a 3% loss would be significant to a small <br />operation while the largest operations could absorb production losses of up to 10% (MLRB <br />1988). <br />As shown on Table 7, field specific percent yield decrease per unit increase in conductivity of <br />irrigation water was calculated for Cox field 11 (6.80%) and Proctor field 6 (7.10%). The <br />species-specific decreased yield per unit increase in conductivity were calculated using ‘Table 3: <br />Potential yield reduction from saline soils for selected crops’ from Colorado State University <br />Extension fact sheet 0.503 - Managing Saline Soils. This table presents EC values when crops <br />begin to display production decline as well as EC values when crops exhibit a 10% decrease. <br />Using those values, percent yield decrease per unit can be calculated. Based on these <br />calculated values, the field salinity thresholds, and the field irrigation water conductance <br />thresholds, the material damage formula yield a crop yield reduction of 0.62% on Cox field 11 <br />and 0.08% on Proctor field 6. Both values are vastly below the 3% threshold for significance <br />demonstrating that no material damage has occurred.