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State Reg. <br />weathering process. A negative ABP indicates. the spoiled material will • <br />have a decrease in pH when acidic elements (pyrites) become soluble <br />during the induced weathering process. <br />Conductivity (Salt). Salt is normally not measured directly as a soil <br />test. The electrical conductivity of soil moisture is measured and taken <br />as an indication of salt level. High salts cause an osmotic pressure <br />barrier to the soil root system interface and inhibit water and nutrient <br />movement into the plant. The tolerance of plants to high soil salts has <br />been well documented (U.S.D.A., 1964). <br />Water Soluble Cations (Ca, Mg, Na). This test reveals the type and <br />concentration of salt that exist in soil water. The ion concentration is <br />directly proportional to the soil conductivity (U.S.D.A., 1964). Calcium <br />and magnesium salts tend to flocculate soil particles where as sodium <br />ions cause soil pads to disperse. Flocculated soil pads have higher water <br />permeability than dispersed soil particles. • <br />Saturation Percentage. This is the amount of water required to <br />completely fill all soil voids. The degree of saturation is highly <br />influenced by the chemical and physical properties of The soils. If the <br />soil's water holding capacity at saturation is below 25%, it is likely that <br />textures are very coarse and soil moisture will reach the "wilting point" <br />during drouth periods. High saturation percentage usually indicates that <br />the soil is high in clay content; especially montmorillonitic type clays. <br />Under extremely high saturation conditions (SP >SO-100%) poor soil <br />water movement, salt build up, crusting, and inhibited root development <br />are likely. <br />Texture Class. <br />The relative proportion of sand, silt, and clay sized <br />particles in a soil generally relate directly to saturation percentage and <br />fertility. Sandy soils tend to have lower saturation percentages and <br />higher permeabilities than clayey soils. Sandy soils are generally less <br />fertile and more droughty Than clayey soils. Soils with a high silt content • <br />are often more susceptible to wind and water erosion. - <br />6-12 <br />