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Custom Soil Resource Report <br />Interfluve <br />A landform composed of the relatively undissected upland or ridge between two <br />adjacent valleys containing streams flowing in the same general direction. An <br />elevated area between two drainageways that sheds water to those <br />drainageways. <br />Interfluve (geomorphology) <br />A geomorphic component of hills consisting of the uppermost, comparatively level <br />or gently sloping area of a hill; shoulders of backwearing hillslopes can narrow the <br />upland or can merge, resulting in a strongly convex shape. <br />Intermittent stream <br />A stream, or reach of a stream, that does not flow year-round but that is commonly <br />dry for 3 or more months out of 12 and whose channel is generally below the local <br />water table. It flows only during wet periods or when it receives ground -water <br />discharge or long, continued contributions from melting snow or other surface and <br />shallow subsurface sources. <br />Invaders <br />On range, plants that encroach into an area and grow after the climax vegetation <br />has been reduced by grazing. Generally, plants invade following disturbance of <br />the surface. <br />Iron depletions <br />See Redoximorphic features. <br />Irrigation <br />Application of water to soils to assist in production of crops. Methods of irrigation <br />are: <br />Basin: Water is applied rapidly to nearly level plains surrounded by levees or dikes. <br />Border. Water is applied at the upper end of a strip in which the lateral flow of <br />water is controlled by small earth ridges called border dikes, or borders. <br />Controlled flooding: Water is released at intervals from closely spaced field ditches <br />and distributed uniformly over the field. <br />Corrugation: Water is applied to small, closely spaced furrows or ditches in fields <br />of close -growing crops or in orchards so that it flows in only one direction. <br />Drip (or trickle): Water is applied slowly and under low pressure to the surface of <br />the soil or into the soil through such applicators as emitters, porous tubing, or <br />perforated pipe. <br />Furrow: Water is applied in small ditches made by cultivation implements. Furrows <br />are used for tree and row crops. <br />Sprinkler: Water is sprayed over the soil surface through pipes or nozzles from a <br />pressure system. <br />Subirrigation: Water is applied in open ditches or tile lines until the water table is <br />raised enough to wet the soil. <br />Wild flooding: Water, released at high points, is allowed to flow onto an area <br />without controlled distribution. <br />37 <br />