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Slope alluvium <br />Sediment gradually transported down the slopes of mountains or hills primarily <br />by nonchannel alluvial processes (i.e., slope-wash processes) and <br />characterized by particle sorting. Lateral particle sorting is evident on long <br />slopes. In a profile sequence, sediments may be distinguished by differences in <br />size and/or specific gravity of rock fragments and may be separated by stone <br />lines. Burnished peds and sorting of rounded or subrounded pebbles or cobbles <br />distinguish these materials from unsorted colluvial deposits. <br />Slow refill <br />The slow filling of ponds, resulting from restricted water transmission in the soil. <br />Slow water movement <br />Restricted downward movement of water through the soil. See Saturated <br />hydraulic conductivity. <br />Sodic (alkali) soil <br />A soil having so high a degree of alkalinity (pH 8.5 or higher) or so high a <br />percentage of exchangeable sodium (15 percent or more of the total <br />exchangeable bases), or both, that plant growth is restricted. <br />Sodic spot (map symbol) <br />An area where the surface layer has a sodium adsorption ratio that is at least <br />10 more than that of the surface layer of the named soils in the surrounding <br />map unit. The surface layer of the surrounding soils has a sodium adsorption <br />ratio of 5 or less. <br />Sodicity <br />The degree to which a soil is affected by exchangeable sodium. Sodicity is <br />expressed as a sodium adsorption ratio (SAR) of a saturation extract, or the <br />ratio of Na+ to Ca++ + Mg++. The degrees of sodicity and their respective ratios <br />are: <br />Slight: Less than 13:1 <br />Moderate: 13-30:1 <br />Strong: More than 30:1 <br />Sodium adsorption ratio (SAR) <br />A measure of the amount of sodium (Na) relative to calcium (Ca) and <br />magnesium (Mg) in the water extract from saturated soil paste. It is the ratio of <br />the Na concentration divided by the square root of one-half of the Ca + Mg <br />concentration. <br />Soft bedrock <br />Bedrock that can be excavated with trenching machines, backhoes, small <br />rippers, and other equipment commonly used in construction. <br />Custom Soil Resource Report <br />60 Index #10