Soil Survey of Lincoln County, West Virginia - Soil Data Mart - US ...

Soil Survey of Lincoln County, West Virginia
rate of water infiltration on a bare soil during periods after prolonged wetting
when the soil is not frozen. These properties are depth to a seasonal high water
table, the infiltration rate and permeability after prolonged wetting, and depth to a
very slowly permeable layer. The slope and the kind of plant cover are not
considered but are separate factors in predicting runoff.
Igneous rock. Rock formed by solidification from a molten or partially molten state.
Major varieties include plutonic and volcanic rock. Examples are andesite, basalt,
and granite.
Illuviation. The movement of soil material from one horizon to another in the soil
profile. Generally, material is removed from an upper horizon and deposited in a
lower horizon.
Impervious soil. A soil through which water, air, or roots penetrate slowly or not at
all. No soil is absolutely impervious to air and water all the time.
Increasers. Species in the climax vegetation that increase in amount as the more
desirable plants are reduced by close grazing. Increasers commonly are the
shorter plants and the less palatable to livestock.
Infiltration. The downward entry of water into the immediate surface of soil or other
material, as contrasted with percolation, which is movement of water through soil
layers or material.
Infiltration capacity. The maximum rate at which water can infiltrate into a soil under
a given set of conditions.
Infiltration rate. The rate at which water penetrates the surface of the soil at any
given instant, usually expressed in inches per hour. The rate can be limited by the
infiltration capacity of the soil or the rate at which water is applied at the surface.
Intake rate. The average rate of water entering the soil under irrigation. Most soils
have a fast initial rate; the rate decreases with application time. Therefore, intake
rate for design purposes is not a constant but is a variable depending on the net
irrigation application. The rate of water intake, in inches per hour, is expressed as
follows:
Less than 0.2 ................................................. very low
0.2 to 0.4 ................................................................ low
0.4 to 0.75 ........................................... moderately low
0.75 to 1.25 .................................................. moderate
1.25 to 1.75 ........................................ moderately high
1.75 to 2.5 ............................................................. high
More than 2.5 ................................................ very high
Interfluve. An elevated area between two drainageways that sheds water to those
drainageways.
Intermittent stream. A stream, or reach of a stream, that flows for prolonged periods
only when it receives ground-water discharge or long, continued contributions
from melting snow or other surface and shallow subsurface sources.
Invaders. On range, plants that encroach into an area and grow after the climax
vegetation has been reduced by grazing. Generally, plants invade following
disturbance of the surface.
Iron depletions. Low-chroma zones having a low content of iron and manganese
oxide because of chemical reduction and removal, but having a clay content
similar to that of the adjacent matrix. A type of redoximorphic depletion.
Irrigation. Application of water to soils to assist in production of crops. Methods of
irrigation are:
Basin.—Water is applied rapidly to nearly level plains surrounded by levees or
dikes.
Border.—Water is applied at the upper end of a strip in which the lateral flow of
water is controlled by small earth ridges called border dikes, or borders.
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