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Distributed in urtheranceo the acts o Congress

o May 8 and June 30,

1914. North CarolinaState University and North

Carolina A&T State Uni-versity commit themselves

to positive action to secure

equal opportunity regard-less o race, color, creed,

national origin, religion,

sex, age, veteran status,or disability. In addition, the

two Universities welcomeall persons without regard

to sexual orientation. North

Carolina State University,North Carolina A&T State

University, U.S. Department

o Agriculture, and localgovernments cooperating.

--

Design and Installation o SDI

Systems in North CarolinaAs a part o the humid Southeast, NorthCarolinas climate, topography, soils, crop-

ping systems, and water sources requirespecial consideration when considering and

implementing a subsurace drip irrigation(SDI) system. This publication is not a step-by-step design manual, but it will help you in

the design process o an SDI system appro-priate to North Carolina.

Irregularly shaped elds commonly ound in

humid areas can result in a system layoutthat diers greatly rom the normal layoutound in the SDI system in an arid or semi-

arid area. Installation is best done whenthe soil moisture is within an optimal range,

which may seriously limit the time when asystem may be installed in North Carolina.

And ewer systems have been installed in hu-mid regions, so ewer proessional installersand less installation equipment are available.

This publication presents both design and in-

stallation considerations to help the grower ina humid area who is considering a SDI sys-

tem. Topics include design criteria; pumps;ltration; chemical injection; valves; mainand submain (header), dripline, and fushing

maniold design; instrumentation and controlsystems; design implementation; installation

tips; and locating an installer.

IntroductionSubsurace drip irrigation (SDI) is similar to

surace drip irrigation, but it has driplines thatare buried beneath the surace. Some drip

systems have lines that are buried up to eightinches deep, but are retrieved annually and

are thus very similar to surace drip systems.This publication ocuses on SDI systems withlines that are permanently installed below

tillage depth (Camp and Lamm, 2003).Although SDI has many important benets

or modern crop production, many challengesalso exist. SDI systems must be careully

designed and installed so that they operatewith proper eciency, and so that ertilizers

and chemicals can be applied in a legal,uniorm, and ecient manner. SDI systemsare expensive and should be designed and

installed to ensure a cost-ecient system.Signicant amounts o technical skill and

management are required to properly oper-ate the systems so that peak eciency and

benets are realized. This means that trainedpersonnel should be involved with the designinstallation, and operation o the system.

Proper training and management skills arevery important to the success o any irrigation

operation, and this is especially true with SDIsystems in which driplines are buried. While

SDI systems have been used successully ormany years in arid and semi-arid locations,the topography, soils, crops, cultural systems

and climate in North Carolina and other humiregions may require a dierent design and

installation.

Beore the design o an SDI system is done,

determine i the intended site is suitable orSDI. Do you have an adequate water sup-

ply, acceptable water quality, and appropriatetopography or an SDI system?

Design CriteriaBegin by collecting inormation needed or asuccessul design. This inormation is reerre

to as design criteria. For an SDI system, thescriteria will include inormation on climate,

crops, soils, and water quality, along withsystem management and operational consid-

erations.

Water RequirementsThe SDI system must deliver the required

amount o water to the crop at the time it isneeded. This is called the crop water require

ment. You will need to supply the peak water requirement, or the amount o water that a

crop uses during its highest water use periodDuring this period o peak water use, your SD

system must deliver that amount o water.

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While you may consider rain to reduce the irrigation re-

quirement or a season, do not consider rain when calculat-ing a peak use rate. Even in humid regions, the probability

o receiving appreciable rain at a critical period is low. Youwant a system that can provide water during a drought. In

addition, moisture in soil storage is normally not consideredwhen designing or peak demand.

Your peak water requirement is normally lower than in aridregions because we have higher humidity and more clouds,

which reduces evapotranspiration. Your crop also infuencesSDI system design. Dierent crops and dierent planting

dates will result in dierent water requirements. I you rotatecrops, design your SDI system to meet the needs o thecrop with the highest water demand. A good rule o thumb

is to size your pumps and main lines to replace a peak cropwater use rate o 0.25 inches per day. This translates to a

pumping fow rate o about 12 gallons per minute (gpm)per acre you plan to irrigate i you run the system 12 hours

per day during the peak water use period and actoring insystem ineciencies. You will need to supply a higher fowrate i you will operate it ewer hours per day and less i you

can operate it more hours.

Management and Operation ConsiderationsAn essential step in the design o an SDI system is toconsider how your use o the area will change over time. Itis not enough to design only or next years crop. A well-de-

signed system should be in operation or 10 to 15 years, soyou must plan or the uture. Consider crop rotation, tillage

systems, and management capacity in the design process.Row crops and eld crops are oten rotated. For example,

corn and cotton may both be grown in rows that are 30-,36-, or 38-inches apart without much dierence in theproduction systems. However, winter wheat and soybeans

will likely have dierent trac patterns than those or row

crops, a act that should be considered when using the SDIsystem or these other crops.

Water QualityWater quality will dictate ltration require-ments, chemical injection requirements,

and management o SDI systems to preventemitter clogging. Emitters may clog due tochemical (precipitates or scale), physical (grit

or particulates like sand and sediment), andbiological (such as algae or bacteria) actors.

Groundwater is generally o higher quality

than surace water and less likely to clog emit-ters. Do check iron and manganese levels, ashigh levels may lead to emitter clogging, and

water may need to be treated.

Many existing and potential water supplysources or SDI systems in North Carolina are

derived rom surace water. The state doesnot tend to have high levels o salts in suracewater, except in some coastal areas. Where

salts are not a problem, emitters are sae rom salt precipi-

tates than can clog emitters in an arid area. Surace watershowever, tend to introduce biological hazards. I you are

considering using wastewater as a source, remember thatthe quality and clogging potential will vary depending upon

the extent o treatment, i any.

Pumps and Power SourcesAs with most irrigation applications, SDI uses centriugalor turbine pumps. Centriugal pumps are more requentlyused to pump water rom surace supplies, such as ponds.

Turbine pumps (a special type o centriugal pump) areused to pump water rom wells, and they may be either

vertical shat or submersible.

How will you power your pumps? Electricity requires lesslabor, but it may not be available where you need it. Three-

phase power is usually required to operate irrigation pumpsgreater than 10 horsepower. I electricity is not available ordesirable, diesel, gasoline, or propane may be used. The

most common alternate power source is usually gasoline-driven engines or small pumps and diesel engines or

larger pumps.

Filtration RequirementsFiltration is critical with any drip system. It is even more

important in an SDI system as lter ailure is costly anddetermining the location o clogged emitters is very di-

cult. Design o a ltration system or SDI systems involvesselection o lter type and lter size (capacity). The size and

type o lter required will depend on the water source andthe kinds (i any) o ertilizer and chemical stock solutions tobe injected. The pH and the amounts o particulate matter,

carbonates, and iron in the water supply will largely deter-mine the ltration system.

Figure 1. Media and disk lters used in SDI systems (courtesy o F.R. Lamm,Kansas State University).

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The types o lters used most oten are sand media (silica

sand or crushed granite), disk, and screen. Media ltersor disk lters are necessary or any surace water source

or wastewater (see Figure 1). In addition, fowing watersources such as a river or stream usually require a sand

separator to remove sand beore it enters the lter system.

Screen lters are used as secondary lters with surace wa-

ter systems or as primary lters with well or municipal watersources. Screen lters vary in shape and size. Screen lters

may vary in size rom 1 inch or 1 acre or less, to 10 inchesin diameter. Mesh sizes range rom 40 to 200; the mesh

size is the number o openings in the lter per square inch.Filters may also be specied by the maximum particle sizein microns that will pass one micron is one-thousandth o

a millimeter. A 200 mesh size is equivalent to 74 micronsand a 120 mesh size is equal to 125 microns. Fine sand

has a diameter o between 125 and 250 microns, so a 120or greater mesh will lter ne sands and larger particles.

Disk lters can be used as primary or secondary lters withsurace water systems and be used as primary lters with

well or municipal water sources. These lters contain a se-ries o grooved plastic disks. Equivalent screen size ranges

rom 40 to 400 mesh (Hanson, et al., 1997) with 40 to200 mesh being the most common. Disk lters have more

surace area than screen lters and are, thereore, bettersuited or higher fow rates. They are also easier to clean.

For any ltration system, the level o ltration (eectivemesh size) is dictated by the emitter and passageway size.In general, the smallest lter opening should be one-tenth

the size o the smallest emitter passageway.

When designing a ltration system, consider lter fush-ing. Most ltration systems are designed or either manualor semi-automatic, or automatic fushing. Flush cycles or

manual and semi-automatic fush systems are manuallyactivated. Flush cycles or automatic systems are activated

either when a pre-set pressure dierential across the ltersis exceeded, or by a pre-set operational time interval. Se-

lection o ltration automation depends upon cost and laborconsiderations.

Both media and disk lters require a minimum pressuredownstream o the lters during the backfush cycle. For

media lters, the required pressure is normally 30 poundsper square inch (psi) and or disk lters it is typically 40 psi.It may be necessary to install a pressure sustaining valve

downstream o the lters that actuates during the fushcycle to maintain the back pressure necessary to fush

properly.

Chemical InjectionChemigation is an inclusive term that reers to both injec-tion o chemicals to prevent or ameliorate emitter clogging

(chlorine or acid), and the injection o chemicals or yourcrops (ertilizers and pesticides). Because drip emittersare small, they clog easily. Along with ltering water, the

capability to inject chlorine and acid is important in prevent-ing clogged emitters. High humidity conditions common in

North Carolina accelerates algae production, so chlorina-

tion is very important i algae are present in the water sup-

ply. Other benets o chemigation are uniorm and timelyapplication o ertilizer, reduced soil compaction due to re-

duced trac in elds, reduced labor requirements, reducedexposure to chemicals, and reduced risk o environmental

contamination.

The design o a chemical injection system involves the

selection o injector type and capacity. I the injectionsystem is to be used to apply ertilizer through your irriga-

tion system (ertigation), size the injection unit or this usesince injection rates or ertilizers are usually much higher

than injection rates or chemicals like liquid chlorine oracid that are added to prevent emitter clogging. Two basictypes o injection systems, the Venturi injector and the

metering pump, are commonly used or injecting ertilizerand other chemicals into drip irrigation systems. Metering

pumps may be positive displacement piston-type pumps,or diaphragm-type pumps. I a diaphragm injection pump

is selected, be sure that the rated pressure is at least asmuch as the pressure you will have at the pump, otherwisethe injection pump will not deliver its rated fow. Be sure

that the injection system has an adjustable injection rate.

Any components that will be in contact with ertilizer, chlo-rine, or acid should be resistant to corrosion. Any chemicalinjection system should be placed so that chemicals are

injected upstream o the ltration system.

Always ollow state laws and chemical labeling require-

ments. Wade, et al. (2003) provides North Carolina guide-lines or the legal and sae injection o chemicals.

ValvesAs with any drip irrigation system, proper selection andplacement o valves are critical. Water fow rate and

pressure throughout the SDI system should be precisely

controlled to ensure ecient and timely water application.Valves play key roles in controlling pressure, fow, anddistribution under dierent conditions to optimize peror-

mance, acilitate management, and reduce maintenance.

Valves used in a complete SDI system include check

valves, shut-o valves, pressure relie valves, remote-control valves, pressure regulators, and air and/or vacuum

relie valves. Valve sizes, maximum working pressure,and valve materials should be selected properly to meet

your systems demands. Oversized valves may not openor close properly and undersized valves may restrict fowand cause excessive pressure loss. Undulating topography

means that extra care will be needed in properly locatingair and/or vacuum relie valves at high points in the system.

Main and Submain DesignProper design guidelines or mainline and submain piping

generally ollow normally accepted design practices orsurace drip and/or sprinkler irrigation systems. Submains,as dened here, are the same as supply maniolds or the

dripline. Supply maniolds are sometimes called headers.See Figure 2 or a typical SDI zone and components. In

normal irrigation design, pipe size is based on economic,riction loss, and water hammer considerations. In an SDI

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system, you must also consider sizing pipe to fush the

system. As pipe size increases, riction loss decreases(reduced pumping cost) but initial cost increases. Main and

submains are normally telescoped or reduced in size aswater is discharged, reducing pipe cost . The major dier-

ence between the design o normal irrigation systemsand SDI systems is the increased importance o properfushing, including the fushing o mainlines, submains, and

driplines. The piping system must be designed not only toallow the fow rate necessary or normal irrigation but also

to allow fow rates to ensure proper fushing velocities in thesystem. Keep submains and fushing maniolds below the

driplines so that solids will tend to collect in the submainsand fushing maniolds rather than in the driplines.

In humid regions, irregular eld shapes are common due totopography and property boundaries. Careully size sub-

mains where eld shape varies. Each dripline lateral mayhave a dierent length and a dierent total fow rate. Base

design or submains on actual fow rates o the driplinesand not on an average fow rate. Pipes or fushing mayalso have diering pipe

diameters because the

fushing fow rate requiredto achieve a desired fush-ing velocity in any section

o a main or submain maybe dierent than the designfowrate (normal operation).

There are two basic fushing

design procedures:Size mainlines and sub-

mains or normal opera-tion (irrigation only).Size pipe based upon

a required fushing fowand velocity.

When designing or irrigationonly, achieve the required

fushing fow and velocitiesin the mainlines by adjust-ing the number o zones

fushed at one time. Whendesigning or fushing, place

valves at the distal end andsize in conjunction with the

pipe to allow fushing fows

and velocities in the largerdiameter sections. In an

above-ground drip system,you may fush submains by

adjusting the number and lo-cation o driplines fushed in

the zone. In an SDI system,you cannot alter the numbero driplines fushed within

a zone. When designing a

submain or irrigation only, the last section or two o pipe,

where operating fows are low, may have insucient fush-ing velocities. Size the piping system to allow fushing o the

entire main or submain to allow a more thorough cleaning ithe need should arise. When designing the system speci-

cally or fushing, the design should aim or velocities o atleast 1.0 oot per second in the largest section o the mainor submain when in fushing mode.

Sometimes an irrigation zone is split into two sections and

manual valves on either hal o the submain allow fushingo hal o the zone at one time (see Figure 2, lower draw-

ing). This gives you fexibility and allows or adjustments infushing fow velocities. While telescoping the submain isdone to ensure adequate fushing velocities in the submain,

too much telescoping may ultimately result in excessiveriction loss in the fush mode. This may result in inadequate

pressure at the dripline inlet to maintain adequate fushingfows and velocities in the dripline.

Figure 2. Typical SDI zone layouts. Lower layout separates zone into two sections or increased

fushing capabilities.

Submain

FlushingManifold

Mainl

ine

Flushing Riser

Air/Vacuum Valve

ControlValve

ToHe

adwo

rks

ToOthe

rZon

es

Tootherzones

Header

Manualvalves

Flushing Riser

Submain

FlushingManifold

Mainl

ine

Flushing Riser

Air/Vacuum Valve

Contr

olVa

lve

ToHe

adwo

rks

ToOthe

rZon

es

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Dripline DesignWith any irrigation system, the design process starts atthe plant and works upstream. Hydraulically speaking, this

means dripline design (dripline selection, specication odripline depth and spacing) comes rst. Dripline selection

involves consideration o emitter spacing, dripline diameterand wall thickness, and emitter fow rates. Also consider

connections between the dripline and the supply and fush-ing maniolds.

Dripline selection will depend upon plant spacing, soil char-acteristics, and dripline durability and hydraulic character-

istics. Dripline diameters range rom 3/8 inch to 1 3/8 inch,and fow rates range rom 0.17 to 1.00 gpmper 100 eet

o dripline. While rigid tubing can be used in SDI systems,drip tape is normally chosen due to its relatively low cost.A minimum drip tape wall thickness o 15 mil is normally

specied. Rigid tubing, rather than drip tape, is sometimesused on sandy soils that do not bridge.

Another consideration is clogging potential. In general,

higher fow rate emitters tend to clog less due to larger fow

passages (Hanson et al., 1997). Also consider your soil.Lower emitter discharge rates may be required on heavytextured soils, such as clay, so that the discharge ratedoes not exceed the hydraulic conductivity o the soil. I the

discharge rate is too high, suracing may occur as watertakes the path o least resistance to the surace via void

spaces.

Dripline depth must be specied. Most systems installed todate in agronomic, tur, and orest crops have placed thedripline between 4 and 18 in below the soil surace (Camp,

1998). In general, dripline depths should be shallower incoarser textured soils and deeper in ner textured soils.

Although soils in North Carolina oten lead to a restriction inthe depth o the root zone, driplines will need to be installed

deep enough to avoid damage rom tillage equipment. Ideep tillage is required (at or deeper than the dripline),tillage must avoid the driplines so precise knowledge o

dripline location is required. While historically this has beena problem, precision guidance systems may reduce the risk

o accidental dripline damage.

Dripline spacing, like depth, depends on soil characteris-tics as well as the crops to be grown. In general, coarsertextured soils will require a narrower dripline spacing than

a ner textured soil, since there is less lateral water move-

ment in coarse soils. Otentimes a critical crop in yourrotation will dictate spacing. In rotations that include a rowcrop, dripline spacing is most oten a multiple o row spac-

ing. Alternate middle rows are common when driplines arespaced on a two-row spacing.

Dripline length is determined by eld length and layout,allowable pressure (and thereore fow) variation within

a zone, and fushing considerations. Irregularly shapedelds may have driplines o dierent lengths. Flow variation

in an SDI system is normally expressed by emission

uniormity (EU), which is dened as the ratio o the average

o the lowest quarter o emitter fow rates to the averageemitter fow rate. The general rule o thumb is to design

or a dripline lateral EU o 90 percent. Most manuacturespublish allowable dripline lateral lengths to maintain a

desired uniormity along the dripline. Driplines need to beperiodically fushed, and the length o dripline laterals willimpact required fushing times. Longer lines need longer

fushing times, both to fush any soil particles or organicmaterial out o the line, and to purge any chemicals that

may have been introduced into the system.

Dripline Flushing Maniold DesignThe fushing maniold at the end o the driplines is ttedwith a fushing riser (see Figure 2) and valve to allow fush-ing o the driplines. When the fushing valve is opened, fow

rates and velocities through the driplines are greater thanthose in normal operational mode. The higher fow veloci-

ties remove settled solids and precipitants rom the systemto help prevent emitter clogging.

Flow regimes may be quite complicated in irregularly-shaped elds with dierent lateral lengths within the same

irrigation zone. Since SDI zones are closed-loop systems,however, pressure tends to equilibrate and zones with

diering lateral lengths can be designed using an averagelateral length.

Determine fushing maniold pipe sizes by considering thefow through the end o the driplines during fushing. Size

the fushing maniold or a fow velocity o at least 1 to 2 eeper second through the laterals to ensure sediment remova

rom the laterals (Lamm et al., 2007). Flushing manioldpipe diameter inceases in the direction o the fushing riser.

It is recommended that telescoping o the fushing mani-old be limited to three equal-length sections and that the

smallest pipe diameter be limited to about two-thirds o thelargest pipe diameter (Lamm and Camp, 2003). Flushingwill increase the fow requirements o the system temporar-

ily, which in turn will decrease the system pressure. In somecases, you may not be able to reach the desired velocity,

especially with pressure-regulated zones. Similarly, someirregular eld shapes may require large amounts o pipingto connect the ends o all the driplines in a particular sec-

tion or zone. When zones are relatively large, the pumpingsystem may not be able to supply the fushing fow rates

required to achieve the desired velocity at the ends o thedriplines. In that case, separate the irrigation zone into two

or possibly three separate fushing maniolds. This separa-tion will allow a proper fushing pressure to be maintained.

A careul balance between fushing velocities in the mani-olds and in the driplines is critical when designing SDI

zones. Several drip tape manuacturers have sotwarethat calculate dripline inlet fushing pressures required

to achieve a 1-ootper-second fushing velocity with anassumed level o back-pressure at the end o the dripline.Other guidance on fushing maniold design may be ound

in Lamm and Camp (2007).

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Instrumentation and ControlsFortunately, components or automating irrigation systemsare common. Automation can pay or itsel by reducing la-

bor requirements and by enabling more precise irrigation. Arelatively permanent SDI system lends itsel to automation.Basic instrumentation starts with meters that help moni-

tor system perormance and that help diagnose potentialproblems. Make sure the installer provides fow meters at

strategic locations, such as submains, or system monitor-ing and to potentially provide eedback or irrigation control.

Pressure gages are also vital in an SDI system to monitorpressure and help diagnose problems. Low pressure and/orincreased fow rates during normal operation can help you

locate a leak.

Irrigation control systems may be open or closed loop.Open loop systems do not incorporate eedback; you set

the amounts and timing o irrigation. Usually a simple ir-rigation controller operated with a clock is available com-mercially. In general, these controllers initiate irrigations at

preset times and control the duration o irrigation by activat-

ing solenoid control valves that serve the irrigation zones.The controllers vary in the number o valves that can becontrolled, the number o valves that can be simultaneously

held open, the number o separate irrigation programsavailable, and the number o start times available or eachprogram. These controllers are not normally set to operate

with eedback, although most oer a rain switch that termi-nates irrigation during precipitation.

Since humid areas like North Carolina by denition haveappreciable rainall, soil moisture may change unpredict-

ably, making it dicult to schedule irrigations. As such, aclosed looped system using eedback rom soil-moisture

sensors to interrupt or adjust irrigations oers many advan-tages. Automation o irrigation using eedback can preventleaching o chemicals and reduce pumping costs by irrigat-

ing only when the crop needs it. Damage rom lightning isthe biggest concern or ully automated irrigation systems in

humid regions.

Implementing the DesignIt is important that the installer o an SDI system, whetherthey are an irrigation dealer, a contract installer, or a grow-er, realize the importance o installing the system exactly as

designed. Site, crop, and management specic issues (e.g.,

dripline spacing, depth, and length, emitter spacing, zon-ing, and control and air valve locations and specications)should have been considered in the design o the systemand so should be installed accordingly. Use caution when

considering a change in the dripline or other specied com-ponents because o cost or other considerations. Changing

a dripline should only be considered i the fow rate, pres-sure rating, and wall thickness are equivalent to designer

specications. I not, the system hydraulics will be changedand dripline lie may be shortened.

Figure 3. Custom-made dripline installation tool is shown in

the top diagram (courtesy o F.R. Lamm, Kansas State Uni-versity); installing dripline with commercial installation tool

is shown in lower photograph.

It may be possible to change the design slightly as long asperormance is not compromised. For example, the con-nections rom the driplines to the maniold may change i

specied parts or connectors are not available rom a localdealer, or i it makes installation easier. I changing parts

make sure they are hydraulically equivalent and be awarethat any changes made to the system can aect its peror-

mance. Consult the designer beore any changes are madeCritical components, such as air and vacuum valves, mustalways meet design specications. Any changes to the

system should be noted on an as-built drawing. These arecopies o the original design that show any modications

that were made during installation.

Begin installation by laying out the system on the eld.Stake where the driplines and maniolds are to be buried, orbed up urrows or use a planter to delineate rows. In eithe

case, it is important to set enough reerence stakes so thatthe system will be installed as designed. Always install per-

manent markers so that maniolds and lines can be locatedater installation or maintenance and planting purposes.

Dripline burial depth and consistency o placement are very

DRIPLINE

SPOOL CARRIER

DRAG BAR

REVERSING TUBE

CHISEL SHANK

SPOOL

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important. I lines are too deep, there wont be enough wa-

ter near the surace or germination, but i its too shallow,tillage practices may be restricted (Lamm et al., 1997). The

proper depth o dripline and maniolds varies dependingupon the crops that will be grown and planned cultivation

practices. Recent advances in installation equipment andguidelines have resulted in more consistent installation oSDI systems (Camp et al., 2000). Examples o tape injec-

tion machines are shown in Figure 3. Gage wheels or skidsused during installation to help place the drip tube at the

design depth will reduce placement depth variability. I youbed up the eld beore installation, it is important to know

the reerence (top o bed, urrow, or midpoint) rom whichdripline depth will be measured.

Timing o installation can be important, especially i youhave clay soils. Soil moisture is a critical consideration

when installing lines in clay soils and will aect dratrequirements and soil disturbance due to the installation

shank. In some cases chiseling or subsoiling o the eldmay be done beore installing the driplines. This eases

installation and breaks up any compacted layer that might

promote suracing o water applied by the dripline. On theother hand, the soil racturing may delay settling o soilaround the dripline, potentially limiting water movementinitially. Close chisel shank marks at the surace to prevent

rodents rom damaging the dripline. Use a drag bar behindthe injector shank or lightly disk or use a rolling cultivator.

In heavy soils, the soil should be dry enough that smear-ing o the side walls o the dripline channel does not occur.

Fall may be the best time to install an SDI system in NorthCarolina, since the soil is normally drier, and it allows timeor soil to settle beore planting.

Installation Tips

I you are installing the system, take the time to talk withknowledgeable consultants, distributors, designers, andother users o SDI systems. This will help you avoid instal-

lation problems. Substantial knowledge is available, but itis not readily available in written orm. Each component othe SDI system has been designed by the manuacturer,

and selected by the designer to provide maximum lie andbenet. However, improper installation can destroy much o

its eectiveness. The ollowing list o tips may be helpul tomake installation easier and successul:

Make sure pumps have adequate capacity to provide

or both irrigation AND fushing. To have adequatefushing capacity, you may need to install additionalzone control valves.

Make certain all above ground equipment (especiallyair release valves, zone control valves, and fushing

risers) are located out o the way o eld equipmentand trac (roads) or they are well protected and well

marked or visibility.

Check installation equipment requently or damage.

Rocks or other items can create a burr on the installa-tion equipment that can damage the drip tape, causing

substantial leaks in the system ater installation.

Install driplines so that the emitter openings ace up-

ward. This will help keep materials that have settled outin the tape rom entering and clogging the emitter.

Veriy the dripline location each year beore planting.The newly planted crop must be properly spaced rom

the tape. I you arent using precision GPS technology,place a metal ring or other small metal object around

the tape at the beginning and ending o the rst (or mul-tiple) row. You will be able to locate it with a relatively

inexpensive metal detector.To help with maintaining dripline depth placement, turn

o the load control or drat setting on the tractorused to pull the installation plow. This will allow the useo the gage wheels on the plow to maintain tape depth

despite varying soil conditions.

Most dripline connector leaks can be avoided by simply

making sure that the dripline is cut square and cleanDripline cuts that have been stretched, pulled, or un-

even will not make a good leak-ree connection.

Protect all control wire and water piping, especially

where it enters or comes out o the ground. Future

damage rom rodents, chemicals, or weed trimmers willbe dicult to locate. It is best to take steps to preventwire damage rom happening. Enclose any aboveg-round control wire in a conduit.

Locating an InstallerSubsurace drip irrigation systems are not common in North

Carolina, so there are not many people with experience insystem installation. Irrigation dealers may provide installa-

tion services in addition to system design and sales. Grow-ers who have had SDI systems installed in the area may

also be a source o inormation. Dealer representatives odripline products otentimes know an installer, or may evenprovide installation equipment especially i their product is

being used. Manuacturers o dripline installation equipmentmay also have inormation on local installers.

Any installer should provide reerences. Be sure to check

them. Bonding or certication rom the Irrigation Associa-tion may be an indicator o a reputable installer. Additional

sources o inormation about installers and other SDI topicsmay be ound on the internet. Two good Web sites arehttp://www.oznet.ksu.edu/sdi and http://www.microirrigation

orum.com.

SummaryThe proper design and installation o any irrigation system,and especially an SDI system, are critical. In North Caro-

lina, design and installation considerations dier rom thosein arid regions. Use the inormation on design consider-

ations to guide you in the design process o an SDI systemthat will work in your elds. Then work with an industry rep-resentative and dealer or consult with your local Extension

agent to nd someone to help you with your design.

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8

ReerencesCamp, C.R. and F.R. Lamm. 2003. Irrigation systems, subsurace

Drip. Encyclopedia Water Science. Marcel Dekker, New York,

NY. pp. 560-564.Camp, C.R., F.R. Lamm, R.G. Evans, and C.J. Phene. 2000. Sub-

surace drip irr igationPast, present, and uture. Proceedings

o the 4th Decennial National Irrigation Symposium, Nov.14-16, Phoenix, AZ. pp 363-372.

Camp, C. R. Subsurace drip irrigation: A review. 1998. Trans.ASAE. 41(5):1353-1367.

Hanson, B., L. Schwankl, S. Grattan, and T. C. Prichard. 1997. Dripirrigation or row crops. Publication 3376, University o Calior-

nia Irrigation Program, University o Caliornia, Davis.

Lamm, F. R., D. H. Rogers, M. Alan, and G. A. Clark. 2003. Designconsiderations or cubsurace drip irrigation systems, Kansas

State University Agricultural Experiment Station and Coop-erative Extension Service Bulletin MF-2578.

Lamm, F. R. and C.R. Camp. 2007. Chapter 6. Subsurace drip

irrigation. in Microirrigation or crop production, pp. 473-551.Elsevier Freddie R. Lamm, James E. Ayars, and Francis S.

Nakayama (Editors)Lamm, F. R., G. A. Clark, M. Yitayew, R. A. Schoneman, R. M.

Mead, and A. D. Schneider. 1997. Installation issues or SDI

systems. Presented at the 1997 ASAE International Meeting,Minneapolis, MN. August 10-14, Paper No. 972074.

Wade, H., D. Seal, C. Clark, B. Walls, K. Messick and G. Grabow.2003. Chemigation and ertigation: Anti-pollution devices or

irrigation systems. Prepared by North Carolina Departmento Agricultural and North Carolina State University

For More InormationGarry L. Grabow, Department o Biological and Agricultural Engi-

neering, North Carolina State University, Campus Box 7625,

Raleigh, NC 27695-7625; e-mail: Garry_Grabow@ncsu.eduKerry Harrison, Department o Biological & Agricultural Engi-

neering, University o Georgia, P.O. Box 1209, Titon, GA.

31793-1209; e-mail: kharriso@uga.eduMichael D. Dukes, Department o Agricultural and Biological

Engineering, University o Florida, P.O. Box 110570, Gaines-ville, FL 32611; e-mail: mddukes@uf.edu

Earl Vories, USDA-ARS University o Missouri Delta Center, P.O.Box 160, Portageville, MO 63873; e-mail: voriese@missouri.

edu

W. Bryan Smith, Clemson University Extension Service, P.O. Box160, Newberry, SC 29108; e-mail: wsmth@clemson.edu

Heping Zhu, USDA-ARS-Application Technology Research Unit1680 Madison Ave., Wooster, OH 44691; e-mail: Zhu.16@

osu.edu

Ahmad Khalilian,Department o Agricultural and Biological Engi-neering, Clemson University, 64 Research Road, Blackville,

SC 29817; e-mail: akhlln@clemson.edu

ThisfactsheetispartofaseriesdealingwithSDIinNorthCaro-

lina.ThefollowingtitlesareavailableontheWebat

http://bae.ncsu.edu:

SDIConsiderationsforNorthCarolinaGrowersand Producers

SiteSelectionforSDISystemsinNorthCarolina

CriticalManagementIssuesforSDISystems

inNorthCarolina

Acknowledgements

Contributions to this fact sheet were made by faculty of the Cooperative Extension Service, the Agricultural Experiment Stations and universities in

Arkansas, Florida, Georgia, Kansas, Louisiana, Maryland, North Carolina, South Carolina and Tennessee, and the USDA-ARS in Georgia and South

Carolina. Activities that resulted in the publication of this document and the companion documents listed were supported by the CSREES multi-state

Prepared by

Garry L. Grabow, Biological and Agricultural Engineering, NC State University

Kerry Harrison, Biological and Agricultural Engineering, University of Georgia

Michael D. Dukes, Biological and Agricultural Engineering, University of Florida

Earl Vories, USDA-ARS University of Missouri Delta Center

W. Bryan Smith, Clemson University Extension Service

Heping Zhu, USDA-ARS-Application Technology Research Unit, Wooster, Ohio

Ahmad Khalilian,

Agricultural and Biological Engineering, Clemson University

Published byNorth Carolina Cooperative Extension Service

250 copies of this public document were printed at a cost of $485.00 or $1.94 per copy.

AG-695-3 4/08.25JMG/SSS

E08-50285