What Is Irrigation? When To Begin Irrigation?

Sprinkler Irrigation BasicsIrrigation ManagementBryan SmithArea Extension AgentWhat is Irrigation?When to begin irrigation? Irrigation is a “balancing act” - too much ortoo little water can both cause problems Irrigation can simply be called thereplacement of water in the soil used byplants - or maintaining a soil water level oramount. (1) When a person walking across the lawncan see his/her footprints (easiest)When to begin irrigation? (1) When a person walking across the lawncan see his/her footprints (easiest) (2) When evapotranspiration losses havereached a percentage of the soil’s waterholding capacity (3) When the soil feels too dry (4) When the plants begin to wither?(Image courtesy Dr. L. B. McCarty)1

How much?Crop Water Use Curve The amount of water applied is setby the plant water need each week.If this is unknown, apply 1 inchper week as a starting point andadjust as necessary (SC receives approximately 50inches of rain each year, but it’snot evenly distributed.)When to Water Newly planted turf - daily until established(0.2 in/day for 7-10 days) Newly planted ornamentals - 1 or 2 timesweekly High water use zones - 1 or 2 times weekly Moderate water use zones - only as needed Low water use zones - don’t water*1 Inch of water is how much? A typical SC household uses 150 gallons ofwater per day per person For a 4 person house average weekly use is4 x 150 gallons x 7 days 4,200 gallons perweek To apply 1 inch of water on 1 acre of landrequires 27,154 gallons of water! Moral - expect a higher water bill!!When is the best time to water? Common sense has said irrigate duringthe day to prevent diseases Watering during the day exposes thesystem to much higher evaporativelosses - as high as 30% or more of thewater pumped can be lost Night watering is much more efficient(15% loss generally) - but is it wise?2

Morning Irrigation andReservoirsWhen is the best time to water? Prevention of diseases is directly connectedto the length of the “leaf wetness” period Watering in the evening or early morning which in effect increases the time the leavesare wet due to the dew fall - can increasedisease problems Watering during the night after dew fall willgenerally not escalate problems Some water systems depend on water tankstorage to meet early morning waterdemands Irrigating during the 5:00 a.m. time periodmay deplete the storage of a water system just in time for the “morning rush.” Timing the irrigation system so thatirrigation is completed earlier can preventwater and pressure shortages.Soils hold water! Coarse soils (sands) hold littlewater - and drain quickly Fine soils (clays) hold a greatdeal of water - and drain slowly Irrigation scheduling shouldconsider soil type and soil waterholding capacity to maximizethe benefit of the systemIrrigation and SoilsWhat does this mean? Sandy soils cannot hold much water and arewell-drained. They should probably beirrigated twice per week. Clay soils hold water quite well and holdquite a bit. Irrigating once per week shouldsuffice Do not irrigate every day! Deep,infrequent watering promotes deeper roots and healthier plantsExceptions to Daily Watering Newly planted sodPotted plantsStreet trees in containersCommercial vegetablesGolf course greens3

Stratified Soils and WaterMovement (110 and 400 minutes)Available Soil WaterAvailable Soil Water as Influenced by Soil Type%Source: Brady and Weil soils bookSoil Infiltration RatesIrrigation EquipmentImpact Sprinklers(image courtesyRainbird Mfg.)*(image courtesyNelson Turf)(image courtesyRainbird Mfg.)4

Stream RotorsGear-drive and Rotor Sprinklers(Image courtesyNelson Turf)(Image courtesyHunter Industries)(courtesy Hunter Mfg.)(Image courtesy Rainbird Mfg.)Pop-up Spray HeadsSpray Head .vs. Sprinkler(image courtesyHunter Mfg.)*(images courtesy Rainbird Mfg.)Spray Heads - fullpattern wetted at once - nostream rotationTimers and Controllers(Images courtesy Rainbird Mfg.)*Sprinklers - single ormultiple rotating streamsValvesGateValveBall Valve(courtesyHammondValve)(courtesySpears Mfg.)Electric Valve(courtesyRainbird Mfg.)5

Valve Box Used when buryingvalves in the yard foreasy identification andaccess Available in varioussizesPipingPVCBlack Roll Pipe(courtesy Tony Tyson,University of Georgia)(courtesy NewberryHardware)(courtesy Corey Tanner,Clemson Extension)“Swing” Pipe and JointsWater Sources(courtesy Rainbird Mfg.)(courtesy HunterIndustries, Inc.)Pump Cycling Electric motors love to run. Operating apump 24 hours a day, 7 days a week willnot harm it. Electric motors hate to start. The startwindings in the motor heat each time theyare used. A single-phase motor should not start moreoften than once every 5 minutes. Thisallows the star windings to cool betweenuses.*WellsStatic waterlevelDynamicwater level6

Water Meter(courtesy Tony Tyson,University of Georgia)Backflow Preventer Used on municipalwater systems available in 5/8”, 3/4”,1”, and larger sizes Adding an “Irrigationmeter” may savemoney in the long run- no sewer charges(courtesy Zurn/Wilkins Company) Available in manydifferent types - needis determined by localwater authority Prevents “backflow”and contamination ofmunicipal watersupply Not required for a wellsystemSprinkler Application PatternSprinkler Head PlacementSprinkler Water Distribution PatternSprinkler SpacingsSprinklers spacedat 100% of wetteddiameterSprinklers spacedat 75% of wetteddiameterCorrect spacing 50% of wetteddiameter7

Fill in center areas*Add pipe sizesA Word on Trenching, Trees andTree Roots(image from “Trees and Turf, Int. Society of Arborculture, 1991)Sprinkler Areas and Flows Full-circles cover100% of the circle Half-circles cover50% of the circle, soneed 50% of the flowof a full circle Quarter-circles cover25% of the circle, soneed 25% of the flowof a full circlePressure and Elevation8

Pressure Losses There are two main types of pressure loss ina residential sprinkler system:(1) Friction loss - pressure loss due to frictionthrough pipe, valves and fittings. Theamount of loss depends on flow rate andpipe size.(2) Elevation loss - pressure lost (or gained)due to elevation. The amount of loss is notdependant on flow rate or pipe size.Elevation Example - Up Hill The vertical elevationdifference is 38 feet Pressure required toreach hilltop: 38 feet x0.433 psi/ft 16.4 psi If the pump supplies50 psi, then there willbe 50 - 16.4 33.6 psiat the hilltopElevation and Water Pressure To pump water up a hill 1 foot high requires0.433 psi, regardless of pipe size or flowrate When pumping water down a 1 foot highhill, the weight of the water adds 0.433 psito the line pressureImage Credits Images are used by permission. Imagecredits are as noted beneath the image. Images marked with a “*” are courtesy ofTony Tyson, University of GeorgiaCooperative Extension ServiceContact InformationBryan SmithClemson Extension Service219 West Laurens StreetLaurens, SC 29360(864) 984-2514 ext 112E-mail: wsmth@clemson.eduIrrigation web site: http://www.clemson.edu/irrig9

a residential sprinkler system: (1) Friction loss -pressure loss due to friction through pipe, valves and fittings. The amount of loss depends on flow rate and pipe size. (2) Elevation loss -pressure lost (or gained) due to elevation. The amount of loss is not dependant on flow rate or pipe size. Elevation and Water Pressure