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The DMG Material Damage Policy document prepared by Banta, 1983 addresses whether <br />"significant" effects have occurred based on the projected crop yield reduction. For large <br />operations (overwinter herd of more than l00 Animal Units) yield reductions up to l0% <br />are considered acceptable. Crop yield reductions greater than 10% may be considered <br />significant. As seen on the attached table, the upper pastuce is nearing, or exceeding, the <br />l0% crop reduction depending upon whether the Ippolito or Maas values are used in the <br />calculation. <br />It has become apparent that the Division's 1998 Material Damage Policy document <br />contains an error with respect to the % yield decrease per unit salinity increase presented <br />in a table on page 4. As discussed with Dennis Jones and Brad Peske, a conversion <br />factor of l.5 must be made to convert the soils EC values to irrigation water EC values. <br />On the calculations shown in the attached table, the salinity threshold values (Aw) and <br />the yield decrease (B) have been converted to water. <br />Ideally, a site specific adjustment factor would be established. The adjustment factor <br />would be representative of local climatic conditions, soil conditions and irrigation <br />practices. To develop this factor, the conductivity of the irrigation water and the specific <br />conductance of representative soil profiles of the root zone would be necessary. Because <br />soil salinity changes with time, the water and soils data would need to be collected during <br />the course of the growing season for an accurate average representation. The goal of this <br />field program would be to develop a site specific adjustment between the conductivity of <br />the soils and water. <br />