Drip irrigation allows fortargeted water applica-

tions, where runoff, leach-ing and wetting ofnon-targeted areas isavoided or completely

eliminated.

What Is Drip Irrigation?

Conserve Water And Irrigate Intelligently

Revenue fromIncreased Yields

Revenue fromIncreased Quality

Labor Costs

Fertilizer Costs

Pesticide Costs

Water Costs

Energy Costs

EnviromentalQuality

Drip irrigation, alsoknown as micro-irri-gation or trickle irri-

gation, is a remarkable watertechnology first developeddecades ago. Today, it is com-monly used all over the worldin agricultural, nursery, green-house, landscape and a vari-ety of industrial applications.In recent years, the demandfor drip irrigation has grownrapidly and for good reason –the technology can help solveserious problems associatedwith water use. The followingwill assist in understandingdrip irrigation such that a sys-tem may be chosen, and ulti-mately operated, intelligently.

Advantages of DripToday it is more important than everto use water resources wisely and toirrigate intelligently. Intelligation™refers to the process of taking fulladvantage of the benefits drip irriga-tion offers. For instance, many farm-ers have enjoyed improvedprofitabilit y with drip by increasingcrop yield and qualit y while at thesame time reducing costs from water,energy, labor, chemical inputs andwater runoff. Many landscapers have

also enjoyed significant water andcapital investment savings usingdrip, while simultaneously improvingplant vigor by delivering water andnutrients directly to the plant rootsand avoiding unnecessary wetting ofplant leaves. In addition, drip irriga-tion allows for targeted, intelligentwater applications, where runoff,leaching and the wetting of non-tar-geted areas such as roads, plantleaves, tree trunks, sidewalks, cars,windows and buildings are avoidedor completely eliminated.

Components of Drip/Micro-Irrigation System

Whether the motivation is improved prof-itabilit y or better resource use, Intelligation™clearly makes sense.

To irrigate intelligently, one must first choosethe right system and then use it properly.Choosing a system can be complicated becauseeach application is slightly different and thereare many options available. However, regard-less of application, it is very important that thesystem delivers a very high application unifor-mit y that will distribute water evenly through-out the system. In general, gravit y irrigationsystems deliver relatively low application uni-formity, sprinklers deliver relatively moderateapplication uniformity, and drip systems de-liver relatively high application uniformity. Athorough understanding of drip irrigation willassist the end user in making the right choicesfor virtually any crop or terrain.

Drip irrigation systems consist of emissiondevices serviced by a water distributionnetwork that ideally includes control zoneequipment. At the water source, water iscontrolled with automatic valves, sometimesamended with nutrients or chemicals, fil-tered and regulated at levels suitable forthe emission devices chosen and plantsbeing grown. From there, water is deliv-ered to each of the emission devices

through a network of PVC and PE pipes.The emission device, whether it is driptape, a drip emitter, jet or micro-sprinkler,then delivers water and nutrients to thesoil where plant roots may nourish theplant. All components have attributes thataffect performance, and that are traded offwith initial, installation, operation andmaintenance costs. A thorough understand-ing will assist in selecting the properequipment to achieve desired expectationsfor the given application. Drip systems aredurable and are built to withstand out-door conditions for reasonable lengths oftime, but care should be taken to avoiddamage by wildlife, foot traffic or fieldequipment. In many cases, the environ-mental conditions will dictate the choiceof emission device for any given applica-tion. A brief description of the threeequipment classes follows:

Drip systems aredurable and are

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1. Emission Devices

Emission devices vary according to theirflow rate, hydraulic characteristics andwetting pattern. The ideal emission de-

vice is durable (withstands outdoor condi-tions), resistant to clogging (large internalpassageways, self flushing), insensitive to pres-sure variation that occurs as a result of slopeand/or lengths of run (pressure compensat-ing), accurate (low manufacturing Coefficientof Variation, or CV) and economically afford-able. Drip emission devices are typically in-stalled on the surface such that there isflexibility in placement, and convenience formanagement. These attributes are achievedvia advanced plastics, hydraulics and injectionmolding technology.

• Drip Tape is a “line-source” productthat incorporates a series of relativelyinexpensive, engineered emission devicesinto a thin walled tube. Water is dis-tributed evenly along the length of thetube through emission devices whichmay be spaced anywhere from 4” to24” apart. To accommodate variouscrops and terrain, tube wall thicknessesare available from .004” to .015” (4 milto 15 mil), emitter flow rates from .07- .34 gph, and pipe diameters from5/8” to 1 3/8”. Drip tape is availablein standard and pressure compensatingmodels, and is used extensively for veg-etable and field row crop cultivation. Itmay be installed above or below theground, and may be retrieved for multi-season reuse or disposed at the end ofeach season. Drip tape is relatively inex-pensive and is ready to install withoutany additional emission device installa-tion labor.

• On-line Emitters are small plastic de-vices which convey small streams offlow from polyethylene (PE) tubing tothe soil. Water then moves through thesoil via capillary flow and creates a wet-ted circle, the size of which is depend-ent upon the soil type, flow rate andirrigation schedule. On-line emitters areattached to the PE tubing wall by in-serting the emitter’s barb shaped basethrough a precisely punched hole. Online emitters offer the user the advan-tage of installing an emission device ex-actly where wanted, and if the emitteris “take-a-part”, it may also be serviced.The disadvantage is that the end usermust manually insert each emitter.Note: Although the ability to self-cleanan emitter is an attractive feature, itshould be viewed as an occasional eventthat is no substitute for proper filtra-tion and maintenance. Drip systemsmay employ hundreds or even thou-sands of emitters, a quantity impracticalto flush by hand.

• In-line Emitters, or Dripline, con-sists of small plastic emission devicessimilar in function to on-line emitters,but in this configuration they are pre-in-serted into the PE tubing at specifiedintervals during the tubing extrusionprocess. The emitters may be cylindricalor flat “boat shaped”, and are attachedto the inner tube wall via a controlledheating/adhesion process. Labor savingsfor the end user may be substantialsince emitters are factory pre-installed.Flexibility is not affected since addi-tional emission devices are easily addedto the tubing in the field if desired.The drawback is that emission devicesmay exist where unneeded, and they arenot serviceable. Unlike all other classifi-cations of emission devices, dripline maybe installed below the surface such thatthe soil surface may be kept dry andsurface damage may be avoided.

Drip emission devices aredesigned to deliver thesame amount of waterfrom each outlet, ensur-ing even distribution and

high uniformity.

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• Foggers are small plastic devices thatemit water as a fairly confined mist, orfog, via a small plastic online device. Inaddition to irrigation water being ap-plied to the soil, temperature may bemanipulated and/or a humid environ-ment may be created. Foggers were orig-inally developed for the citrus industry,but work well for potted plants orhanging baskets as well where confinedroots require frequent wetting.

• Jets are small plastic devices mountedon risers and/or stakes that jettisonwater through the air as separatestreams which create finger shaped pat-terns of water in the soil. A variety offinger patterns are available includingfull circle, half circle, hi/low trajectory,butterfly, etc. The versatility of patternsprovides a great deal of flexibility forthe end user to accurately apply wateronly where wanted, such as envelopingeach tree in an orchard without wettingthe trunk, or in landscape beds withodd shapes, or in potted plants.

• Micro-sprinklers are small plastic de-vices that emit water in a full circlespray/sprinkler pattern through the airvia a rotating spinner. The device is at-tached to the PE lateral tubing via aseparate plastic stake or via a combina-tion of a plastic stake fitted with alength of PE micro-tubing. The advan-tage is that water is applied over alarger area using only one emission de-vice, and that operating pressures andapplication rates are low. A possibledrawback is that, similar to conventionalsprinklers, water is delivered throughthe air and may be applied to non-tar-get areas such roads, tree trunks, foliageor other non-target areas. In addition,water applied through the air is affectedby wind. It should be noted that a per-formance overlap exists where the higherflow rate ranges of micro-sprinklers ap-proach the lower flow rate ranges ofconventional sprinklers.

2. Distribution System

Once the emission device is chosen,a system of filters, chemical injec-tors, pipes, valves and fittings must

be constructed to deliver water reliably,safely and efficiently to each outlet, and tofacilitate system maintenance. The majorcategories are as follows:

• Filters are used to remove organic andinorganic debris from the water thatcould potentially clog the emission de-vices. In agriculture, sand media filters,screen filters or disk type filters arecommonly used, and may be cleansedmanually, semi-automatically or automati-cally. Even where potable water is used,which is typical of landscaping applica-tions, disc or screen filters should beinstalled since scale and chemical precip-itants may occur which present a poten-tial clogging hazard. Depending on the

Drip application ratescan be tailored to fit thesoil and plant type,allowing for flexible

water applications aboveor below the soil surface.

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emission device chosen, the degree offiltration should be 80-200 mesh.

• Chemical Injectors are typically in-stalled in drip irrigation system in orderto facilitate system maintenance withchlorine or acid, and also to supply nu-trients or other liquid or gaseous sub-stances to the plants being irrigated.Whatever type of injector chosen, ex-treme care should be taken to ensurethat the system includes proper safetyand backflow prevention devices.

• Pipe – PVC pipe is widely used totransport water from the water sourceto irrigation equipment of all types. Indrip/micro-irrigation systems, it is typi-cally used in the control zone and inthe delivery network as both mainlineand sub-mainline. In some cases, it mayalso be used as the lateral servicing theemission devices. White PVC pipe isnot UV resistant.

• Tubing – PE tubing is widely used asthe lateral pipe servicing the emissiondevices. It is available in numerous di-ameters, wall thicknesses and reellengths with varying pressure ratings andhydraulic characteristics. PE tubing, re-gardless of the color, is UV resistant.

• Fittings – PVC pipe connections aretypically made using solvent welded fit-tings, while PE tubing is usually con-nected via compression, insert orring-lock type fittings.

• Flush Valves are used to periodicallycleanse the conveyance and emission de-vice components of organic and inor-ganic debris that could clog theemission devices if left unchecked. Theymay be simple manual valves fitted atthe ends of mainlines, sub-mainlinesand/or laterals, semi-automatic valvesthat flush only at start-up or shut-down,or fully automated solenoid valves.

• Air/vacuum Relief Valves – Toavoid general equipment failure, piperupture or pipe blockage, A/V reliefvalves are used to expel air that buildsup in the pipeline network duringstartup and operation. A/V relief valvesare also used to allow air to enter thepipeline network as water exits at shut-down. This avoids undesirable vacuumsuction in both the pipelines and theemission devices. A/V relief valves aretypically installed at high elevationpoints, at control points, and at peri-odic pipeline intervals.

• Pressure Regulators are installed toprotect downstream components fromexcessive pressures. They are especiallyimportant in drip/micro systems becausethe plastic and PE construction materi-als typically have lower pressure ratingsthan conventional sprinkler systems.

In addition to water, dripirrigation systems may bedesigned to efficiently de-liver fertilizers and/or pro-tective chemicals directlyto the plant’s root zone.

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3. Control Zone Equipment

Now the drip irrigation system mustbe monitored and operated. It can-not be stressed enough how impor-

tant the first two categories (flow metersand pressure gauges) are to assess perform-ance and guidance for operation, and howimportant the last two categories (valvesand controllers) are to deriving the maxi-mum benefit from a drip irrigation system.

• System Flow Meters are available ina range of sizes and types, and com-monly provide both instantaneous andcumulative water flow with an accuracyof approximately two percent. Flow me-ters may also be fitted with electricalanalog conversion units that are capableof transmitting flow rate data to a cen-tralized irrigation control computer.

A micro-irrigation system offers the useran unprecedented degree of control overhis water and power costs, and over thegrowing conditions of his crop. To takefull advantage of this ability to controlthe irrigation system, it is necessary tohave useful feedback information onflow rates and total water applied dur-ing a given time period. Accurate flowrate information is also indispensable forthe analysis of crop response to waterand nutrients, and for monitoring thecontinuing performance of the irrigationsystem. A good quality system flowmeter is therefore an essential part of awell designed micro-irrigation system.

• Pressure Gauges are an essentialitem for drip systems since visual moni-toring is often impractical or impossible.Pressure gauges placed at the pump sta-tion, before and after the filter station,and upstream and downstream of eachcontrol valve will provide an immediateindication of system performance. Ifpressures are too low, a leak could beindicated, a filter plugged or a valvejammed. If pressure are too high, thesystem could be plugged or a valve maybe set incorrectly. Similar to a flowmeter, accurate pressure information isessential part of a well designed andoperated drip system.

• Zone Control Valves are used tocontrol the flow of water to the variousblocks or network zones. They may besimple manually operated valves, or fullyautomated solenoid activated on/off orpressure reducing valves. They may beco-located at the pump station or otherPoint of Connection (POC), or may bedispersed throughout the farm or land-scape.

• Irrigation Controllers are used toautomatically start and stop irrigationevents by sending electronic current tosolenoid activated valves. The electroniccurrent is controlled by a user definedschedule that is entered for each zonecontrol valve. More sophisticated con-trollers may allow automatic adjustmentof the program based on sensor inputssuch as weather (plant water use orrain), system flow or system pressure.

Drip irrigation systemscan be fully automated,offering an unprece-

dented degree of controlover water and power

costs, and over the crop’sgrowing conditions.

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Definition of DripDrip may be defined according to a number of performance parameters including flowrates, wetting pattern, pressure rating and construction material. Regardless of the spe-cific type, make or model of a drip irrigation system or component, its performance istypically characterized as follows:

• Water is applied at a low flow rate – emission device flow rates are typically measuredin gallons per hour (GPH), resulting in low application rates.

• Water is applied for long periods of time – irrigation duration may be hours ratherthan minutes when the application rate is low.

• Water is applied frequently – irrigation events may occur daily, or even multipletimes per day, when the application rate is low.

• Water is applied at low pressure – operating pressures typically range between 10-30psi, rarely exceeding 60 psi, for most emission devices.

• Water is applied directly to the soil and the plant’s root zone –water drips, or sprays, directly onto the soil and into the targeted plant’s root zonewithout wetting the plant or non-target areas, and without regard to the presence ofwind. Depending on soil type and emission device, wetting patterns typically rangefrom 0.5-6.0 feet for emitters and up to 40 feet for micro jets or sprays.

• Water is applied through numerous emission devices – in point source drip, eachplant is fitted with at least one emission device to service the plant’s water needs.In broadcast drip, a gridwork of emission devices wets the entire area, servicing allplants within the wetted area.

• Water is filtered – to avoid plugging the relatively small passages inside drip emitters,150-200 mesh filters are used to remove mineral or organic materials from the irri-gation water.

• Fertigation is enabled – since water is applied directly to the root zone, there is anopportunity to apply nutrients along with the water.

• Operation can be automated – drip irrigation systems are often controlled with sole-noid enabled valves that can be automatically actuated according to a user definedprogram entered into an irrigation controller.

Defin

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Typical Layout of a Drip Irrigation System

The ToroCompanyMicro-Irrigation Business1588 N. Marshall Avenue, El Cajon, CA 92020-1523, USATel: +1 (800) 333-8125 or +1 (619) 562-2950Fax: +1 (800) 892-1822 or +1 (619) 258-9973

www.toromicroirrigation.comALT142 08/07

Comparing Drip/Micro to Sprinkler and Flood IrrigationDrip/Micro Sprinklers Gravity

Emission device flow rate GPH GPM N/AOperating pressure 4-60 psi 30-90 psi LowDuration of irrigation seconds, minutes, or hours minutes hours, daysFrequency of irrigation daily weekly monthlyFiltration 150-200 mesh none noneQuantity of devices More Less N/ASize/cost of each device Less More N/AWetting patterns .5-40 feet 5-100 feet BroadcastWetting plants Typically no Typically yes Typically noWetting non-targeted areas Typically no Typically yes Typically yesRunoff on slopes Typically no Typically yes Typically yes

In summary, utilizing drip irrigation may be advantageous in many applications. Whether the enduser wishes to improve profitability or simply reduce water use, there are a variety of emissiondevices and supporting system components to choose from such that plants may be irrigatedefficiently, regardless of type or quantity. Once the drip system itself is more thoroughly under-stood, the next step is to use the system properly such that all potential benefits may be realized.

Comparison with Gravity and Sprinkler Irrigation

Since sprinkler irrigation is commonly used in bothagriculture and in the landscape, one can furtherdefine drip by comparing it directly to sprinkler ir-

rigation performance parameters. Conventional sprinklerstypically apply water at a flow rate measured in gallonsper minute (GPM) rather than GPH. As a result, appli-cation rates are generally higher, causing irrigation dura-tion to be shorter and irrigation events less frequent.Higher application rates may also result in runoff ifthey exceed the soil and slope’s ability to absorb water.Sprinklers typically operate at pressures ranging from35-90 psi or more, spreading water through the air viaspray or rotor type mechanical devices with wide distri-bution patterns. Thus, the plant material is typicallywetted before water reaches the soil and root-zone, andnon-targeted areas such as roads may be wetted as well.

Since sprinkler irrigation systems apply water throughthe air, wind may affect wetting patterns as well.

Gravity irrigation is commonly used in agriculture to ir-rigate crops via a network of ditches, pipes, furrowsand/or basins. After leaving ditches or pipelines, un-pressurized water flows down furrows or across basinsfrom one end of the field to the other, using gravityand a slight elevation drop for propulsion. On the pos-itive side, gravity irrigation does not consume energy topressurize the water and does not require high capitalinvestments. However, the drawbacks to gravity versusdrip include relatively poor application uniformity, highevaporative losses, unsuitability for hilly terrain, longlengths of run or sandy soils, and the inability to tar-get the crop’s rootzone or to spoon feed applications asneeded on a frequent basis.

Drip irrigation providessuperior uniformity,reduced evaporation,and less disease than

other irrigation methods.

What Is Drip Irrigation?

Conserve Water And Irrigate Intelligently