Laserfiche WebLink
Saturation Percentage. Saturation percentage is a useful parameter for detecting low • <br />water-holding capacity and clarifying the degree of sodic hazard as indicated by SAR <br />(Merrill et el., 1987). The degree of saturation is highly influenced by [he physical <br />properties of the medium. Soils tend to be droughty, coarse textured, and readily leeched <br />of nutrients when the water holding capacity at saturation is 25 percent or less. A high <br />saturation percentage (greater than 85 percent) indicates a fine textured medium with <br />potentially poor air and water permeability characteristics. <br />Particle Size (Texture). Texture refers to the relative proportion of sand, silt, and <br />clay sized particles and generally relates directly to saturation percentage. Texture <br />influences water infiltration end percolation, water and nutrient retention, surface <br />crusting, shrinkage end swelling, frost heaving, compaction, and erodibility. Textural <br />problems are generally encountered when either sand contents approach 85 percent or clay <br />levels are greater than 50 percent. Soils with high silt or very fine send content are <br />often more susceptible to wind and water erosion. <br />Dominant 4ater Soluble Cations (Ca, Mg, and Na), end SAR. The water soluble Ca, Mg, and <br />Na analyses reveal the type end concentration of salt that exists in solution. The ion • <br />concentration is directly proportional to the soil conductivity (USDA, 7969). The ratio <br />of soluble Na to Ce plus Mg, referred [o as SAR, is commonly used to predict both chemical <br />and physical properties of growth mediums. The ratio is en indicator of dispersion, <br />flocculation, porosity, infiltration, permeability, erodibility, Surface Crusting, end <br />seedling emergence. SAR reveals the relative dominance of sodium in the soil water <br />solution. <br />Boron. This essential plant micronutrient serves as an activator in numerous enzyme <br />systems (Donahue, et el., 1977). Boron is needed by plants in only very minute amounts <br />and the range between boron deficiency end boron excess is not great. If present in <br />excess concentrations, plant toxicity symptoms may appear. Also as pX decreases, the <br />solubility and the potential for boron toxicity increases. Elevated boron levels are <br />frequently found in avid soils where salts have accumulated near the surface. Xigh levels <br />of calcium in the soil decrease the severity of boron toxicity (Traynor, 1980). <br />Molybdenum end Selenium. Some native plants tend to accumulate high levels of molybdenum <br />and selenium in their tissues. High levels of selenium ere often associated with primary • <br />and secondary indicator plants (USDA, 1957). Elevated molybdenum levels often occur in <br />18 <br />