Selecting an Irrigation System. Ronald F. Gronwald Water Management Engineer USDA NRCS Greensboro, NC. An Irrigation System is more than the Application Method. Source of water Management of water Conveyance of water Application of water Capture and reuse (Tailwater Recovery). Field.
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Selecting an Irrigation System Ronald F. Gronwald Water Management Engineer USDA NRCS Greensboro, NC
An Irrigation System is more than the Application Method • Source of water • Management of water • Conveyance of water • Application of water • Capture and reuse (Tailwater Recovery)
Field Source 1 2 1 3 7 1 Pressure flow to field 2 Sprinkler application 3 Runoff 4 Capture 5,6,7 Return flow Tailwater Pond 4 6 5
Irrigation Systems • Surface Irrigation • Subsurface Irrigation • Sprinkler Irrigation • Microirrigation
Surface Irrigation Water applied by gravity flow • Basin Irrigation – Entire field is flooded • Furrow Irrigation – Water fed into small channels • Border Irrigation – Strips of land divided by low dikes are flooded sequentially
Suitable crops • rice (grows best when its roots are submerged • pastures, e.g. alfalfa, clover • trees, e.g. citrus, bananas • Crops which are broadcast, such as cereals (Basin and Border Irrigation) • Row crops (Furrow Irrigation) • Not suited to crops which cannot stand in wet or waterlogged conditions for periods longer than 24 hours. (root and tuber crops) • Potatoes • Beets and carrots (require loose, well-drained soils)
Suitable soils and land slope • Flatter land surfaces are best suited to surface irrigation methods • Loamy soils are best (to avoid permanent saturation of the soil) • Sands are not recommended for surface irrigation as, due to the high infiltration rate, percolation losses can be high.
Water requirements • A high volume, intermittent flow rate is required
Advantages of Surface Irrigation • It is the simplest of all irrigation systems • Low initial cost • Low energy costs if gravity can be used to supply the water • Works well in odd shaped fields
Disadvantages of Surface Irrigation • High maintenance requirements • Inefficient in water use • Nutrients and pesticides are lost by deep percolation below the root zone • Is not suitable for crops which grow below ground such as potatoes, peanuts, sugar beets and carrots.
Subsurface Irrigation • Irrigation water is applied below the ground surface, thus raising the water table to the crop root zone
Suitable Crops • Most crops are well suited for subsurface irrigation except very deep rooted crops such as alfalfa and cotton.
Suitable Slopes Works best on flat fields
Suitable Soils • The best suited soils have an impermeable layer 5 or more feet below the surface • Water is supplied to the roots by upward capillary action (upflux). Medium textured soils are best. (Fine sandy loams)
Advantages of Subsurface Irrigation • Permits storage of water in the lower soil profile • Reduces pumping costs • Can be incorporated into an existing drainage system with low additional cost • Captures plant nutrients at or near the water table for future use by plants
Disadvantages of Subsurface Irrigation • Labor intensive to adjust elevation of weirs to change from drainage mode to irrigation mode and back again after heavy rains • System cost can be high in soils with low hydraulic conductivity or rolling topography • Water quality must be high
Sprinkler Irrigation • Water is applied similarly to natural rainfall • Pumps supply water under pressure • Water is distributed through a system of pipes to sprinkler heads • Water breaks up into small water drops which fall to the ground • Must be designed and operated to ensure a uniform application of water
Types of Sprinkler Systems • Hand Move or Wheel Line • Big Gun • Solid Set • Center Pivot • Linear Move • LEPA (Low Energy Precision Application) • LESA (Low Elevation Spray Application) • LPIC (Low Pressure IN Canopy) • MESA (Mid Elevation Spray Application) • Variable Rate
Suitable crops • Row crops • Field crops • Tree crops • Big Gun not recommended for irrigation of delicate crops such as lettuce that may be damaged by large drops.
Suitable slopes • Adaptable to any farmable slope, uniform or undulating • Best when operated parallel to the land contour (to minimize pressure changes along the lines)
Suitable soils • Best suited to sandy soils with high infiltration rates • Adaptable to most soils if runoff is avoided • Not suitable for soils which easily form a crust (use fine sprays to avoid crusting)
Water requirements • The best water sources for a sprinkler system are a wells and ponds. • Low volumes but a continuous supply is needed
Advantages of Travelers (Big Gun) • Low initial cost • Very mobile - can be used in multiple fields • Works well in odd shaped fields • Can be used to apply manure or lagoon effluent
Disadvantages of Travelers • Requires high operating pressure • Uses more energy than other systems • Requires a grassed travel lane • Delivers large droplets which may damage some plants or damage soil surface • Has high instantaneous delivery rate
Advantages of Hand Move Systems • Low initial cost • Works well in odd shaped fields
Disadvantages of Hand Move Systems • High labor costs • Must be moved from once to 3 times a day • Difficult to use on large fields or with tall crops such as corn
Advantages of Wheel Line Systems • Low initial cost • Works well in level fields that are square or rectangular • Can be used in trapezoidal shaped fields by adding or removing pipe sections from one or both ends • Lower labor cost than hand move systems
Disadvantages of Wheel Line Systems • Can only be used on low growing crops • Difficult to move in the direction parallel to the pipe • Rolling topography makes alignment difficult
Advantages of Solid Set Systems • Can irrigate entire fields at once • Can be used for multiple purposes • Irrigation • Frost protection • Crop cooling • Chemical applications
Disadvantages of Solid Set Systems • High cost • Risers and sprinkler heads may be damaged by equipment during the growing season
Advantages of Center Pivots • Easy to use • Low labor costs • One system can irrigate a large field • When used with corner attachment, can irrigate almost any size and shape field • Adaptable to many different soils, variable terrain and management objectives.
Disadvantages of Center Pivots • High initial cost • Has variable application rates across the system (highest at the outer portion of the system. • Requires a complex control system • Vulnerable to lightning and ice damage • Typically requires three-phase power supply
Advantages of Linear-move Systems • Easy to use • Low labor costs • One system can irrigate more than one field • Water is applied uniformly across the length of the system • Water intake can be from a ditch or from a drag hose.
Disadvantages of Linear-move Systems • High initial cost • Best suited to rectangular fields with a length to width ratio of at least 2:1 • It is not well adapted to fields with rolling terrain