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KRCD Irrigation Services, Offered at No Cost to Growers in the District

K I N G S R I V E R C O N S E R V A T I O N D I S T R I C T

IRRIGATIONN E W SVolume 14, No. 3 May - June 2003Plant stress is an important consideration in cropproduction. Proper irrigation management controls

when and how much stress occurs. Many growersmanage their own irrigations; some hire others tohandle the details. Ron Brase and Randy Kazarian

are consultants who bring a considerable amount ofirrigation experience to the their clients.

Ron Brase is the president of an agricultural con-sulting business in Fresno. His organization pro-vides diversified technical services including irriga-tion scheduling, pest and nutrition management,and crop damage and land development assess-ments. He has worked in this field for 25 years.

Randy Kazarian has literally worked with grapessince he was old enough to drive a tractor on his

father's farm. Currently, he manages approximately8,000 acres of vineyards for himself, family, andclients. Of this, about 1,000 acres are raisins withthe balance being wine grapes. Randy covers anarea from Chowchilla to Bakersfield plus someobservational work around Lodi and Paso Robles.

To these men, irrigation scheduling is both an artand a science. "We employ a variety of techniques tomeasure soil moisture as well as stress levels withinthe plant," says Brase. "We primarily use neutronprobes to monitor soil moisture and plant pressurechambers to measure leaf and stem water potential."

"The tools available enable me to adjust my irriga-tion schedules constantly, " says Kazarian.Scheduling irrigations is a constant part of hisduties. "I adjust my schedules weekly, based on pre-dicted weather and current soil and plant condi-tions." Excess water promotes vegetative growth,

while insufficient water will overstress the vines andruin quality.

What about irrigation management and crop stress?"It's all in the timing of the stress," says Brase."Properly timed stress discourages excessive vegeta-

Stress Management

tive growth and promotes fruit development with thecharacteristics a customer wants." The management

of soil moisture and vine stress is also critical tocanopy management. Brase adds, "With well-man-aged canopies, fruit exposure is enhanced and dis-ease pressure is reduced."

Many of Kazarian's growers deliver grapes for use in wineries. Each winery looks for specific qualitycharacteristics in the grapes that they buy, and thismakes his job a little trickier. "Grape growers typi-cally think in tons per acre and brix (sugar content),not color or taste. Taste is rapidly becoming one ofthe most important factors in grape selection. Many

wineries will produce small batches of wine from

selected loads then run blind taste tests on them. Ifa grower ranks well, it could mean the differencebetween a renewal contract being offered or not,"says Kazarian.

When asked how irrigation decisions are madebecause of a wet or dry winter, both responded thatthe local conditions dictate the schedule. "It'sdynamic" says Kazarian. "Each area is different.Each variety is different. Sometimes it is different inthe same block and variety. A grower must considerand prioritize their goals when planning an irriga-tion strategy."

Randy Kazarian and Ron Brase

Field Evaluation Services

Determine the uniformity of a drip, furrow, border,

or sprinkler system. Best month for evaluation:

_____________________________

The Irrigation pump also needs testing.

Irrigation System: __________________________________

Crop: ______________________________________________

Acres: _____________________________________________

Contact Person: ____________________________________

Phone:_____________________________________________

Mail To: Eric Athorp

Kings River Conservation District

4886 E. Jensen Avenue, Fresno, CA 93725

or email your information to:

eathorp@krcd.org

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How To Be EfficientBeing efficient is important for every grower.Greater yields are obtained with fewer inputs.Efficient irrigation depends upon both the uniformi-ty of the irrigation and the ratio of beneficially used

water to the total applied.

What is irrigation efficiency (IE)? It is the ratio ofbeneficial use to total input into a system. Beneficialuse is defined as crop ET plus the added leachingfraction. This is determined by accounting for all theinputs and outputs within a defined area. For ourpurposes, the defined area is from the soil surface tothe bottom of the effective root zone on a field level.The concept can be expanded to analyze an entiredistrict or groundwater basin.

Inputs consist of effective rainfall and irrigationwater. Effective rainfall is that fraction of total rain-

fall that actually infiltrates the soil profile and is notlost to evaporation or runoff. A simplified but rea-sonable estimate for effective rainfall is 50 percent ofthe yearly total. Outputs include surface runoff, cropET, and the deep percolation of water beyond theamount budgeted for leaching.

Application Efficiency (AE) is one method for evalu-ating efficiency:

AE* = Average Depth Contributing to Target x 100

Average Depth of Water Applied

*from Burt et al Irrigation Performance Measures: Efficiency and

Uniformity.Journal of Irrigation and Drainage Engineering, 1987

The target is defined as the consumption of water(either amount since last irrigation or season total)by the crop plus any applied for leaching. For exam-ple, if the target amount is 44 inches (40 inches ET,4 inches leaching) and the average applied was 50inches, the efficiency is 88 percent.

However, AE can sometimes mask problems withina field. If this water was not applied with a high

degree of uniformity, the usefulness of this numberis low. Distribution Uniformity (DU) must be takeninto account in order to define the true water useefficiency. DU is a measure of how evenly irrigation

water is applied. The goal is to deliver the sameamount of water to every plant. The AE may be veryhigh but if the DU is low then some areas will beseriously over irrigated while others are under irri-gated causing multiple problems including pooryields. Figure 1 shows this situation.

How does a grower apply water more efficiently?The first step is to improve DU. There are standard

methods for measuring DU for all irrigation systemtypes. Once the problem areas are identified, cor-rective actions can be taken to increase the watersupply to the driest areas without increasing theamount applied to the wetter areas. For pressurizedsystems, this usually involves a redistribution of sys-tem pressures and emitter maintenance. Surfacesystems may require land leveling or different fur-row configurations to correct non-uniformity. Pumprepairs can also be of benefit as higher flow rates caneither reduce set run times or increase set sizes.

Figure 2 shows a field with a higher DU. In thiscase, less water is wasted to deep percolation andthe drier part of the field is receiving more water

without increasing the total amount applied.

A KRCD irrigation review can provide growers withthe necessary tools to improve DU and use available

water with greater efficiency. This service is provid-ed free of charge to growers within the KRCD serv-ice area and can be scheduled using the coupon onthe front or by calling the KRCD Irrigation Specialistat 237-5567 ext. 117.

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Adapted from Burt & Styles, ITRC 1994

IRRIGATIONN E W S

Reprint freely with credit to:Irrigation News, a bimonthly

publication of the KingsRiver Conservation District

For more information contactan Irrigation Specialist at(559) 237-5567 ext. 117

eathorp@krcd.org

RETURN SERVICE REQUESTED

Kings River Conservation District4886 E. Jensen AvenueFresno, CA 93725-1899

NON-PROFIT ORG.U.S. Postage

PAIDPERMIT NO. 1687

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Figure 1 - Low Uniformity Condition

Figure 2 - Average Uniformity Condition

DepthofWater

Percent of Field

DepthofWater

Percent of Field

AE = 100% IE = 92% DU = 75%

AE = 100% IE = 87% DU = 60%

3 Irrigation Requirement

Low 1/4 Average = 2.25

3 Irrigation Requirement

Low 1/4 Average = 1.8

OverIrrigation

SevereUnder Irrigation

Deep PercolationReduced

UnderIrrigation Reduced