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Physical Soil Properties-Georgetown Area, Colorado, Parts of Clear Creek, Soil Physical Properties - Robert Fulton <br />Gilpin, and Park Counties <br />Physical Soil Properties <br />This table shows estimates of some physical characteristics and features that affect <br />soil behavior. These estimates are given for the layers of each soil in the survey <br />area. The estimates are based on field observations and on test data for these and <br />similar soils. <br />Depth to the upper and lower boundaries of each layer is indicated. <br />Particle size is the effective diameter of a soil particle as measured by <br />sedimentation, sieving, or micrometric methods. Particle sizes are expressed as <br />classes with specific effective diameter class limits. The broad classes are sand, <br />silt, and clay, ranging from the larger to the smaller. <br />Sand as a soil separate consists of mineral soil particles that are 0.05 millimeter to <br />2 millimeters in diameter. In this table, the estimated sand content of each soil layer <br />is given as a percentage, by weight, of the soil material that is less than 2 millimeters <br />in diameter. <br />Silt as a soil separate consists of mineral soil particles that are 0.002 to 0.05 <br />millimeter in diameter. In this table, the estimated silt content of each soil layer is <br />given as a percentage, by weight, of the soil material that is less than 2 millimeters <br />in diameter. <br />Clay as a soil separate consists of mineral soil particles that are less than 0.002 <br />millimeter in diameter. In this table, the estimated clay content of each soil layer is <br />given as a percentage, by weight, of the soil material that is less than 2 millimeters <br />in diameter. <br />The content of sand, silt, and clay affects the physical behavior of a soil. Particle <br />size is important for engineering and agronomic interpretations, for determination <br />of soil hydrologic qualities, and for soil classification. <br />The amount and kind of clay affect the fertility and physical condition of the soil and <br />the ability of the soil to adsorb cations and to retain moisture. They influence shrink- <br />swell potential, saturated hydraulic conductivity (Ksat), plasticity, the ease of soil <br />dispersion, and other soil properties. The amount and kind of clay in a soil also <br />affect tillage and earthmoving operations. <br />Moist bulk density is the weight of soil (ovendry) per unit volume. Volume is <br />measured when the soil is at field moisture capacity, that is, the moisture content <br />at 1/3- or 1/10-bar (33kPa or 10kPa) moisture tension. Weight is determined after <br />the soil is dried at 105 degrees C. In the table, the estimated moist bulk density of <br />each soil horizon is expressed in grams per cubic centimeter of soil material that is <br />less than 2 millimeters in diameter. Bulk density data are used to compute linear <br />extensibility, shrink-swell potential, available water capacity, total pore space, and <br />other soil properties. The moist bulk density of a soil indicates the pore space <br />available for water and roots. Depending on soil texture, a bulk density of more than <br />1.4 can restrict water storage and root penetration. Moist bulk density is influenced <br />by texture, kind of clay, content of organic matter, and soil structure. <br />Saturated hydraulic conductivity (Ksat) refers to the ease with which pores in a <br />saturated soil transmit water. The estimates in the table are expressed in terms of <br />micrometers per second. They are based on soil characteristics observed in the <br />field, particularly structure, porosity, and texture. Saturated hydraulic conductivity <br />(Ksat) is considered in the design of soil drainage systems and septic tank <br />absorption fields. <br />USDA Natural Resources Web Soil Survey 12!28!2010 <br />,? Conservation Service National Cooperative Soil Survey Page 1 of 6