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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 S

Volume 14, No. 4 September - October 2003

New System Pros and ConsDaniel Moseley has a modest sized operation nearSelma. Until recently, he irrigated his mix of fruit

trees with a conventional surface system, whichdated back to the 1930's. Moseley described the sur-

face system as "not flexible enough" and has recent-ly replaced it with microsprayers that allow greater

flexibility, uniformity and control.

Three factors led Moseley to the decision to change

irrigation systems. "Labor was a major factor" hesaid. "I would have to have an irrigator here all day

under the old system, for the entire time I was irri-gating. Now I check the system periodically while it

is running. I have cut my labor costs from six hoursper day for someone else to one hour of my time."

Water use was the second reason. "My well wouldpump about 1,000 gpm for 18 hours at a time during

an irrigation under the old system. Now, my flowsare reduced to about 350 gpm for 10 hours, and I

cover more acres."

Energy was the third reason. "I seem to be running

my pumping plant less than before, and that is trans-

lating into lower costs," says Moseley. "The systemis on a timer and I can set it to run when I want. I

also had soil moisture sensors installed this summerso I can monitor the performance more closely."

Some people think that changing systems is a long,drawn-out process. Not so in this case.

"Construction took about three weeks, from thetrenching to laying the laterals to installing thesprinkler heads," says Moseley. "It went very

smoothly."

A change in irrigation systems necessitates a changein management practices. Moseley agrees. "Weed

control is now an issue that I am dealing with. Idon't plow my middles, and the grasses there and inthe berms have grown so tall that they interfere with

the spray patterns. It will take some adjustments,like using a preemergent herbicide to keep the

weeds down. Using the moisture meters is new, too.I will need to get used to that as well," says Moseley.

"Also, I have found that the components are more'delicate' than I anticipated."

Other problems that have arisen include the rutswhere the trenching took place and some breakage

of lines when the system was first turned on. "I thinkthe contractor could have filled the trenches better,

but they have been very good about replacing teesand couplers that pop off due to the system pres-

sure."

Asked what he would do differently or what he

would tell others who are thinking of making thechange from one system to another, Moseley replied,

"Do your homework. Research the type of systemthat you want, know the components that you need

so that you can ask intelligent questions of thedesigner, without just taking what they say for grant-ed. You need understand your system, because once

it's in, it is yours to maintain." Good advice.

New Method to Estimate Grape YieldsEstimating grape yields can require a considerable amount of time and labor. In the August 2003 issue of

Trellis Talk, a new technique is being researched that can tell a grower what their yield potential is bymeasuring the tension changes on the trellis wire.

Julie Tarara, a research horticulturalist with USDA/ARS in Washington, is using load cells to measure thechanges in wire tension as the fruit develops. The signal from the load cell is recorded in a data logger for

later retrieval. Her research has been going on for the last three years.

According to Tarara, wine grapes are better suited for this technique, since canopy development is arrestedafter fruit set. Other vineyards could benefit as well, but the additional vine growth present would need tobe accounted for. Additional questions need to be answered before the technique is used commercially, but

the potential is considerable.

The original article can be seen at www.trellistalk.com.

Daniel Moseley discusses his

conversion experiences.

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System Design Considerations

When a grower decides to look at changing irriga-tion systems, the possibilities may seem overwhelm-

ing. Here are some basic guidelines to help pointgrowers in the right direction.

The major factors to consider are the things that willnot change with the system. These include the soiltype, slope of the field, water source, water qualityand crop type. Other factors are the capital cost of

the system, operation and maintenance costs, andmanagement considerations.

Soils

The texture of a soil (the ratio of sand, silt, and clay)determines its infiltration rate and its ability to hold

water, the water holding capacity (WHC). Coarse,

sandy soils have low WHC values and high infiltra-tion rates, while finer clay soils have high WHC val-

ues and lower infiltration rates. Water quality cannegatively impact infiltration rates without a corre-

sponding change in WHC.

Sandy soils with their low WHC (less than 1.2 inch-

es of water per foot) require frequent irrigations toavoid plant stress. Such soils are better irrigated

with sprinkler or microirrigation systems. Loam andclay soils have higher WHC values, and can support

longer irrigation intervals depending upon the cropgrown. As the texture of the soil becomes finer, therisk of having water pond on the surface during irri-

gation increases. This can create an anaerobic (nooxygen) situation within the soil that harms the roots

and prevents water and nutrient uptake. Undersuch conditions, it is critical to match application

and infiltration rates.

Restrictive layers in the subsoil require a differentapproach to irrigation. Adding water to the rootzone at a rate faster than the subsoil can drain

results in an impoundment of water above theimpermeable layer. If allowed to remain, this water

will bring previously leached salts back into the rootzone or even to the soil surface. Intensive manage-

ment and reduced application rates are required toavoid this condition.

Slope

The slope of the field also determines the suitability

of an irrigation method. Flat or nearly flat terrain works well for all irrigation methods. As slopes

increase, erosion becomes a factor and the irrigation

method employed must reflect that risk. Methodssuch as sprinklers or microirrigation can bring suchland into production.

Water Source and Quality

The timing of available water can limit system

options, unless a supplemental source exists. Forsurface systems, it is critical that the supply remains

even during the course of the season so that all areasof the field receive water at equal intervals. Well

water can supplement surface deliveries but this

adds cost to the system.

Poor water quality will increase the cost of operationand maintenance of any pressurized system.

Surface water usually contains organic matter thatrequires filtration or chemical treatment prior to usein microirrigation systems. Well water frequently

contains dissolved minerals that can impact systemperformance and the physical properties of a soil.

The pH of the water can have an adverse affect oncertain components such as aluminum pipe.

Management Considerations

Capital and operational costs vary by system. As the

complexity increases, the capital costs increase.Highly engineered systems are the most expensive

but can be the most efficient in controlling the appli-cation of irrigation water. Such systems are most

practical for high value crops or in areas wherewater is expensive.

Maintenance costs of such systems are higher due to

increased component content. Emitters require

replacement due to plugging, wear or simple breakage.

The table below is a summary of system selection con-

siderations. If you are considering changing irrigation

methods or have any other irrigation related questions,call the KRCD Irrigation Specialist at 237-5567.

IRRIGATIONN E W S

Reprint freely with credit to:

Irrigation News, a bimonthlypublication of the Kings

River Conservation District

For more information contact

Eric Athorp at(559) 237-5567 ext 117

www.krcd.org

RETURN SERVICE REQUESTED

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

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PERMIT NO. 1687FRESNO, CA

Relative Comparisons of Irrigation System Types and Primary Concerns

System Type Soil Type Slope

Water

Quality Capital Cost

Operational

Cost Filtration

Crop

Suitability

Flood Loam to Clay Mild EC LowLow to

ModerateNone All

Furrow Loam to Clay Mild EC Low Moderate None All

Sprinkler All All EC, pHModerate

to HighModerate Sand Only All

Drip* All All EC, pH High Moderate RequiredTrees,

Vines

Microsprinklers All All EC, pH HighModerate

to HighRequired Trees

*Sub Surface drip is available for row crop applications