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Irrigation Glossary <br />Lateral Page 4 of 7 <br />Pipe(s) that go from the control valves to the sprinklers or drip emitter tubes. <br />Leaching <br />Moving soluble materials down through the soil profile with the water. <br />Leaching Requirement <br />Amount of water that is required to flush excessive soil salts below the plant root zone. [in, <br />mm) <br />LEPA (Low-Energy Precision Application) <br />The use of drop tubes on a center pivot or lateral-move systems to apply water at low <br />pressures very near or directly onto the soil surface. This increases efficiency and <br />uniformity. Furrow dikes are typically required to avoid runoff. Often confused with LESA <br />(low elevation spray application) and MESA (mid elevation spray application). <br />Level Basin <br />Water is applied at relatively high flow rates to a completely level field. Precision laser <br />leveling is required to achieve the level fields suitable for this method. <br />Line Source <br />Continuous sources of water emitted along a line. Usually associated with drip irrigation <br />where emitters are spaced at regular Intervals in poly-tubing. <br />Mainline <br />Pipe(s) from the water source to the control valves. <br />Management Allowable Depletion (MAD) <br />Also known as maximum allowable depletion, management allowable deficit, management <br />allowable deficiency, allowable soil depletion or allowable soil water depletion. The portion <br />of plant available water that is allowed for plant use prior to irrigation based in plant and <br />management considerations. Usually a % of the available water capacity. (%, decimal] <br />Matric Potential <br />The force (measured in units of negative pressure) that the soil exerts (pulls) on water. <br />[bars, kPa] <br />Motor Efficiency <br />Ratio of the power delivered to the pump by the motor to the input power supplied to the <br />motor. A three phase electric motor is inherently more efficient, less expensive, and lasts <br />longer than a single phase electric motor. [%, decimal] <br />Nan-Point-Source Pollution <br />Small amounts of pollution coming from large areas (fields) without a well-defined source. <br />Nozzle <br />Final orifice through which water passes from the sprinkler to the atmosphere. Sprinkler <br />flow rate is largely determined by the nozzle size (orifice diameter) and pressure. <br />Osmotic Potential <br />The equivalent force that a salinity differential can cause across a semi-permeable <br />membrane (plant root). [bars, kPa] <br />Permanent Wilting Point (PWP) <br />Soil moisture content at which plants can no longer get water from the soil and will wilt and <br />die. [%, decimal, in/ft, mfm] <br />iittp-.//irrigation.wsu.edu/glossary.php <br />1/7/2008 <br />83