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Conductivity ISalinityl~ Salinity is normally not measured directly as a soil test. The electrical <br />conductivity IECI of the soil solution is measured and taken as an indication of salt level. <br />Soluble salts influence the quantity of water available to plants and total dissolved solids <br />concentration in ground water. High salts cause en osmotic pressure barrier to the soil root <br />system interface and inhibit water end nutrient movement into the plant. The tolerance of <br />plants to high soil salt levels is species dependent and has been well documented (USDA, 1969 <br />and Donahue et al., 1977). Salinity levels ere most critical during germination and most <br />detrimental in hot dry climates and on south facing slopes than in other landscape positions. <br />Saturation Percentage. Saturation percentage is a useful parameter for detecting low water- <br />holding capacity end clarifying the degree of sodic hazard as indicated by SAR (Merrill et al., <br />19871. The degree of saturation is highly influenced by the physical properties of the medium. <br />Soils tend to be droughty, coarse textured, end readily leached of nutrients when the water <br />holding capacity at saturation is 25 percent or less. A high saturation percentage (greater than <br />85 percent) indicates a fine textured medium with potentially poor air and water permeability <br />characteristics. <br />Particle Size ITexturel~ Texture refers to the relative proportion of sand, silt, and clay sized <br />particles and generally relates directly to saturation percentage. Texture influences water <br />infiltration and percolation, water end nutrient retention, surface crusting, shrinkage and <br />• swelling, frost heaving, compaction, end erodibility. Textural problems ere generally <br />encountered when either sand contents approach 65 percent or clay levels are greater than 50 <br />percent. Soils with high silt or very fine sand content are often more susceptible to wind and <br />water erosion. <br />Dominant Water Soluble Cations ICa, Mg, and Nal, and SAR. The water soluble Ca, Mg, and <br />Na analyses reveal the type and concentration of salt that exists in solution. The ion <br />concentration is directly proportional to the soil conductivity (USDA, 19691. The ratio of <br />soluble Na to Ca plus Mg, referred to as SAR, is commonly used to predict both chemical and <br />physical properties of growth mediums. The ratio is an indicator of dispersion, flocculation, <br />porosity, infiltration, permeability, erodibility, surface crusting, and seedling emergence. SAR <br />reveals the relative dominance of sodium in the soil water solution. <br /> <br />11 Revised 9/98 <br />