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The grower's options at this point are limited to liq-

uid fertil izers or anhydrous ammonia. Each has itsadvantages and risks. Anhydrous is dangerous to

handle, and can be difficult to meter out, but it pro-vides the most ni trogen per uni t of material (83 per-

cent) of any fertil izer. It wi ll burn any foliage itcomes in contact with, and should only be handledby trained personnel.

Liquid fertilizer formulations are generally safe to

handle and easy to apply. They can be appl ied asdirect soil in jection, as a carri er in pesticide appli ca-

tions, or directly by irrigation water. Irrigationappli ed ferti li zer has the advantage of not damaging

the plants or compacting the soil during appli cation.Injection knives do not prune roots, the tractor or i tstoolbar does not damage plants, and the appl ication

can occur after the rows have closed over.

Given the current climate regarding the quality ofsurface waters within California, and the growing

concern over groundwater quality and usage, it isimportant to discuss the regulations regarding themixi ng of chemicals into i rrigation water.

Fertigation is defined as the application of fertilizer

materials wi th irri gation water. Chemigation refersto the application of pesticides with the irrigation

system. Whi le the basic requi rements for both aresimilar, care should be taken to insure that you arein compliance with the strictest requirement when

performing chemigation. Consult with the labelrestrictions on the material you are applying.

Common to all the requirements is a physical means

of backflow prevention. There are two commonmethods used to achieve this. The first method is aphysical separation between the discharge and the

ir rigation system. This prevents the formation of asiphon, which can draw "contaminated" water back

in to the source. When using ditch water, the in takefor the irrigation system is located at the highest

point of the irrigation system.(conti nued on back page)

Volume 16 N o. 3 M ay- June 2005

Fertilizer, like water, is a cost that growers must

manage properly. Ferti li zer costs are rising i n di rectrelation to the cost of the energy necessary to pro-

duce and apply them. The over appl ication of a fer-tilizer runs the risk of groundwater contamination,

surface water contamination via erosion or off sitemovement of tail water, as well as increased pestcontrol costs. It i s important that a grower budget

their fertilizer applications to insure that the materi-als are appli ed to the crop when it is needed most.

Sound fertilizer management begins with a soil

analysis. The soil acts li ke a bank account for thecrop, carrying balances of water and nu trients from

season to season, waiting for the crop to make itswi thdrawals. H ow much of any one nutr ient presentwithin the soil depends upon the parent material of

the soil , the previous crop and ferti li zation practices.

A typical soil analysis will include the major nutri-ents of nitrogen, phosphorus and potassium. Other

nutr ients that may be mentioned include sul fur, cal-cium, magnesium and some of the minor nutrients.The results can be reported in either parts per mil-

li on (ppm) or pounds per acre.

Which fertili zer formulation and application methodis best? There is no correct answer to that question.

Some crops are more sensitive to the fertilizer for-mulation than others, and price will be a determin-ing factor as well . Dry formulations work well

regardless of the appli cation method (band or broad-cast), and the mix can be tailored to the needs of the

crop. They are typically applied prior to planti ng forfield crops or early in the spring for permanent

crops.

Once the season is under way, plant tissue samples

should be collected to determi ne the nutri tional sta-tus of the crop. If a healthy crop is present, addi-

tional fertil izer may be recommended to support theload. At thi s point, access to the field can be restrict -

ed and the most cost effective means to apply addi-tional fertili zer i s with the i rrigation water.

KRCD I rrigation Servic

es Offere

d at NO COST to Growers in the D istrict

Field Eva

luation S

ervi c

e

s Contact Person:___________________________Determine the uniformi ty of a drip, fu rrow,

border, or spri nkl er system. Phone:___________________________________

Best month to evaluate ____________________ M ail this form to:Eric Athorp

The I rrigati on pump also needs testi ng. Ki ngs River Conservati on Di strict4886 E. Jensen Avenue

Type of System ___________________________ Fresno, CA 93725

Type of Crop _____________________________ Or email your informat ion to:

eathorp@krcd.orgAcres ____________________________________

Water. Power. Environment.

Reli able resources for the Vall ey.

IRRIGATION NEWSGood Ferti l izer M anagement is a M ust

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Good Fert i l izer M anagement is a M ust (cont.)

When the water is shut off, the water naturally drainsaway from the source. When a pump is used, the dis-

charge must either be located above the highest levelthat water within the standpipe could reach (an airgap) or a backfl ow prevention valve must be installed.

A backflow prevention valve is a spring loaded valvethat opens while the pump is running, but as soon aswater begins to retreat into the pipe column, the spring

closes a rubber plate onto the discharge pipe, prevent-ing the movement of water into the well . A vacuumbreaker valve (air vent) must be located between the

pump and the backflow valve to allow air into the pipecolumn as the water retreats.

Pressure systems typical ly have two available points for

chemical injection, before or after the fil tration system.M any feel that the best place to inject is upstream ofthe filters, where any precipitated material can be fil-

tered out before it gets to the emi tters. For those thatare only applying liquid fertilizers, downstream of the

fil ters is preferred. This prevents the discharge ofmaterial i n the backflush water.

In systems that are designed to inject pest control

chemicals, the use of check valves at the source tankand at the injector site is required. This prevents thepressurized water from being forced backwards

through the system and into the source tank. Thesevalves can also be electrically controlled, so that they

automatically close when the power is shut off.

A simple method of material injection is through theuse of a venturi . Thi s device relies on the pressure di f-ferential between the upstream and downstream sides

of some device wi thi n the system. Some growerschoose to use a throttli ng valve to create thi s differen-

tial but th is reduces the overall efficiency of the pump-ing plant by creating excess pressure and restricting

flow. Others rely on the natural di fference in pressurecreated by the filter station. The in jected material i sintroduced into the water stream as the high-pressure

water moves into the lower pressure side of the venturi .

Another common method is the use of an injectorpump. This pump takes the source water, raises the

pressure, runs the pressuri zed water through a venturiand discharges the mixed water into the system. Somepumps are set up to directly pump the material into the

water stream at control led rates. These systems aremore common on acid injection systems, as it mini-

mizes the piping involved.

Calibration is also a key factor in saving money on fer-til izer. The first number that a grower needs to know isthe rate of irri gation within the field, in acres/hour. The

next number the grower needs is the pounds of materi-al per gall on of fertil izer. I f the target application is 35

pounds per acre, the i rri gation rate is 5 acres per hourand the fertilizer has 10 pounds per gallon of the

desired nutri ent, then the rate should be set at 17.5 gal-lons per hour (35 pounds/acre x 5 acres/hour divided by

10 pounds/gallon equals 17.5 gallons/hour), or 37ounces per minute (17.5 gallons/hour x 128 ounces/gal-lon divided by 60 minutes/hour equals 37.3

ounces/minute). Any change in irri gation rate requiresa corresponding change in appli cation rate to main tain

a uniform application.

If you have any questions regarding the precautionsneeded for irrigation-applied fertilizers, or any otherirrigation related question, call Eric Athorp at (559)

237-5567, ext. 117.

IRRIGATIONN E W S

Reprint freely with credit to:

Irrigation News, a bimonthlypublication of the Kings

River Conservation Di stri ct

For more information contact

Eric Athorp at(559) 237-5567 ext 117

www.krcd.org

RETURN SERVICE REQUESTED

Kings River Conservation Distri ct4886 E. Jensen AvenueFresno, CA 93725-1899

NON-PROFIT ORG.U.S. Postage

PAIDPERM IT N O. 1687

FRESNO, CA

AgLine M enu Options

In order to make your usage of the AgLine phone system easier, here is a quick guide to themenu options. The Agline phone number is (559) 237-4800.

Option 1 is Refe

rence ETo, as measured at the Kearney Ag Station, Parl ier.

Opti ons 2, 3, and 4 relate to Tree and Vine crops. Option 2 is the Predicted water use for thenext 7 days, Option 3 is the Actual water use for the last 7 days, and Option 4 is for Season toDa

te.

Field and Row Crops are covered in Options 5, 6, and 7. Option 5 is the P

re

dicted water use

for the next 7 days, Option 6 is the Actual water use for the last 7 days, and Option 7 is for

Season to Date.