UniversityofCaliforniaSmallGrains-Alfalfa/ForagesFieldDay-May11,2017

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DripIrrigationStudiesinAlfalfaAliMontazar-DepartmentofPlantSciences,UCD;amontazar@ucdavis.edu

DanieleZaccaria,DepartmentofLand,Air,andWaterResources:dzaccaria@ucdavis.eduKhaledBali,KearneyAgriculturalResearch&ExtensionCenter;kmbali@ucanr.edu

DanielPutnam-DepartmentofPlantSciences,UCD;dhputnam@ucdavis.edu

In California, about 80-85% of alfalfa production is accomplished utilizing surface irrigationsystems,15%using sprinkler systemsofvarious types.Approximately2-3%utilize subsurfacedrip currently, a number thatwas very close to zero 6 years ago. However, there is stronginterest inmorewater-use efficient application systems, given thedynamics ofwater supplyandthepotentialtoimproveyields.

Over the past 3-year period, we have beenobserving and surveying installation of subsurfacedrip irrigation (SDI) systems on 23 farms inCalifornia and Arizona, and conducting controlledstudieson theUniversityResearchFarms.Thishasbeen a tremendous learning experience – we arelearning from growers as they learn how to adaptthis technology, andproviding suggestionsonhowits success might be improved. It is an ongoinglearningcurveforallofus.

SDI trial at Kearney Research and ExtensionCenter.SDIhasthecapacitytoimproveyieldsandimprovewateruseefficiencyinalfalfa.

Yield. It is quite likely that alfalfa yields mayimprove utilizing SDI in alfalfa vs. floodirrigation. Growers in the long-seasonedenvironment of Central and SouthernCalifornia and Arizona have reported yieldsaveraging 3 ton/acre over their check-flood fields, at least in the first several years.Experimental data has reported 20-35%increases in yield vs. surface systems incontrolledstudies.

YSDI=0.98YFlood+3.00R2=0.74

UniversityofCaliforniaSmallGrains-Alfalfa/ForagesFieldDay-May11,2017

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Fig1.Alfalfayields(SDIvs.conventionalcheckflood)

In a well-designed and properly managed SDI, there islesssoilevaporation,morecroptranspiration,norunoff,and no/less-deep percolation. Water savingpotential!

Better water distribution Uniformity overtime. SDI has the ability to quickly apply auniform irrigation to anentire field. This isnot possible with most surface systems.Depending upon flow rates, many surfacesystemsrequirefrom3-12daysirrigating80-100 acre field. Thus, one side of the fieldmay get water much later than the otherside,limitingyields.

Better water distribution Uniformity overSpace. Check flood systems have built-inlimitations in uniformity due to differenttimes available for water infiltration atdifferent places in the field. Often,water infloodedfieldsneedstomovemorethan1,300feet, which takes 10-14 hours – so differentamounts of water are provided in differentsections (Figure 2). One of the keyadvantages of SDI systems is to apply watermoreuniformlyacrossafield.

Fig2.Wasterdistributiontheentirefield(surfaceirrigation)

Fig3.MatchingalfalfaETandappliedwaterthroughSDIovertheseason

UniversityofCaliforniaSmallGrains-Alfalfa/ForagesFieldDay-May11,2017

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ThekeylimitationsofSDIincludecostofinstallationandrodentdamage.Rodentdamage.Rodentdamage,particularlythepotentialforgopherdamage,isprobablythekeypracticaldisadvantageandmainbarrierofadaptationofSDIcurrently.Somegrowershave‘walkedaway’fromlargeinvestmentsduetorodentinfestations.Alfalfa,particularlysprinkler-

Fig4.DailyalfalfaETandirrigationappliedovertheseason

Fig6.Wirelesssoilmoisturemonitoringnetwork

Two more advantages of SDI: (1) Prevention ofwetting-dryingcycles(preventscrackingclaysfromdamaging roots, common on heavy soils. Oxygento roots may improve depending upon soil andmanagement); (2) Longer potential stand life andlessweedpressure

ET-basedirrigationscheduling:followingcropETandmonitoringsoilmoisturestatus

Fig5.Soilwatertensionovertheseason(SDIvs.sprinkler)

UniversityofCaliforniaSmallGrains-Alfalfa/ForagesFieldDay-May11,2017

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orSDI-irrigatedalfalfaisanidealhabitatforgophers.Highlevelsofmanagementarerequiredtomanagerodents.

SDIsystemshavethepromiseofreducedlaborrequirements,andthishasbeendemonstratedonseveralfarms.Certainly,awell-designedsystemcanbenearlyfullyautomated,comparedwithmanysurfacesystems,whichrequirefulltimeirrigators.However,additionallaborislikelytoberequiredforscoutingforrodentinfestationsandfixingleaks.

Costs. The cost of SDI installations has been amajor disadvantage of SDI systems in alfalfahistorically.System installationsmaycostbetween$1,000/acre and 2,600/acre depending uponspecificsofthefarm.However,thesecostscanbejustified if yields are improvedand/orpriceof theproduct is sufficient to cover costs. We haveestimated the yield required to justify the cost atbetween0.5ton/acreand1.5tons/acredependinguponspecificcostsandthepriceofhay.

§ GopherFence § SettingTraps § BurrowFumigation(aluminumphosphide,Carbonmonoxide) § Baiting(Strychnine) § ContinualMonitoringandRemovalEfforts

Floodirrigation

Gophercontrol?

Positive profitability of SDI for the long-season regions, but perhaps not for the short-season Intermountain areas.

Fig7.Leaks&driptapedamageduetorodents

UCwebresourcesforSDIcanbefoundat:http://alfalfa.ucdavis.edu