“Drainage class (natural)” refers to the frequency and duration of wet periods under conditions similar to those under which the soil formed. Alterations of the water regime by human activities, either through drainage or irrigation, are not a consideration unless they have significantly changed the morphology of the soil. Seven classes of natural soil drainage …Continue reading “Iowa Soil Drainage Class Maps [gSSURGO]”
“Water table” refers to a saturated zone in the soil. It occurs during specified months. Estimates of the upper limit are based mainly on observations of the water table at selected sites and on evidence of a saturated zone, namely grayish colors (redoximorphic depletions) in the soil. A saturated zone that lasts for less than …Continue reading “Iowa Depth to Water Table Maps [gSSURGO]”
Soil reaction is a measure of acidity or alkalinity. It is important in selecting crops and other plants, in evaluating soil amendments for fertility and stabilization, and in determining the risk of corrosion. In general, soils that are either highly alkaline or highly acid are likely to be very corrosive to steel. The most common …Continue reading “Iowa Soil pH Maps [gSSURGO]”
Saturated hydraulic conductivity (Ksat) refers to the ease with which pores in a saturated soil transmit water. The estimates are expressed in terms of micrometers per second. They are based on soil characteristics observed in the field, particularly structure, porosity, and texture. Saturated hydraulic conductivity is considered in the design of soil drainage systems and …Continue reading “Iowa Soil Saturated Hydraulic Conductivity (Ksat) Maps [gSSURGO]”
Clay as a soil separate consists of mineral soil particles that are less than 0.002 mm in diameter. The estimated clay content of each soil layer is given as a percentage, by weight, of the soil material that is less than 2 mm in diameter. The amount and kind of clay affect the fertility and …Continue reading “Iowa Soil Clay Content Maps [gSSURGO]”
Silt as a soil separate consists of mineral soil particles that are 0.002 to 0.05 mm in diameter. In the database, the estimated silt content of each soil layer is given as a percentage, by weight, of the soil material that is less than 2 mm in diameter. The content of sand, silt, and clay …Continue reading “Iowa Soil Silt Content Maps [gSSURGO]”
Sand as a soil separate consists of mineral soil particles that are 0.05 mm to 2 mm in diameter. In the database, the estimated sand content of each soil layer is given as a percentage, by weight, of the soil material that is less than 2 mm in diameter. The content of sand, silt, and …Continue reading “Iowa Soil Sand Content Maps [gSSURGO]”
Water content, -15 bar, is the amount of soil water retained at a tension of -15 bars, expressed as a volumetric percentage of the whole soil material. Water retained at -15 bars is significant in the determination of soil water-retention difference, which is used as the initial estimation of available water capacity for some soils. …Continue reading “Iowa Soil Water Content – 15 Bar Maps (wilting point) [gSSURGO]”
Soil water content at -1/3 bar is the amount of soil water retained at a suction tension of 1/3 bar, expressed as a volumetric percentage of the whole soil. Water retained at -1/3 bar is significant in the determination of soil water-retention difference, which is used as the initial estimation of available water capacity for …Continue reading “Iowa Soil Water Content – 1/3 Bar Maps (field capacity) [gSSURGO]”
Bulk density, one-third bar, is the oven-dry weight of the soil material less than 2 mm in size per unit volume of soil at water tension of -0.33 bar (-33 kPa), expressed in grams per cubic centimeter. Bulk density data are used to compute linear extensibility, shrink-swell potential, available water capacity, total pore space, and …Continue reading “Iowa Soil Bulk Density – 1/3 Bar Maps [gSSURGO]”
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