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not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
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Copyright 2005, Board of Trustees, University
.j CIRCULAR 276 B
liuv 1i J 10
I.F.A.S. Univ. of Florida
LIQUID FERTILIZER MATERIALS
INTO IRRIGATION SYSTEMS
D. S. HARRISON
Florida Cooperative Extension Service
Institute of Food and Agricultural Sciences
University of Florida, Gainesville
INJECTION OF LIQUID FERTILIZER
INTO IRRIGATION SYSTEMS
Dalton S. Harrison
Applying fertilizer materials through irrigation water is fre-
quently called "fertigation." It has been practiced with varying
degrees of success in many areas of the United States since 1930.
There many advantages in using an irrigation system to
apply fertilizer. A major advantage is that labor required for
both irrigation and fertilizer application is only slightly greater
than that required for irrigation alone. In addition to good sur-
face distribution, excellent control can usually be maintained on
placement depth of some fertilizer materials, especially nitrogen.
As another advantage, nutrients become available to plants
sooner than when applied on the ground, since they are already
in solution. And, less fertilizer may be required throughout the
But, there are certain disadvantages to fertilizer application
through irrigation systems, namely: (a) an improperly designed
system will not give equal distribution, (b) lower cost fertilizer
materials often cannot be used, (c) localized fertilizer placement
cannot be obtained as in conventional band placed applications,
(d) materials containing phosphoric acid concentrate near the
surface of the soil and anhydrous and free ammonia in other
nitrogen solutions may be lost into the air when applied through
irrigation water, and (e) free ammonia may also damage the
green foliage, as well as some other problems.
Persons trained in soils and use of fertilizer should be con-
sulted before promiscuously injecting any material in an irriga-
Methods of Injection
Suction intake or "two-valve": This is perhaps the easiest
method but it is applicable only to shallow well centrifugal
pumping systems. Install as follows:
Connect one line from open fertilizer tank to suction line of
pump, thus letting pump draw fertilizer into the intake side. A
valve is required in this line to adjust intake rate and to cut off
fertilizer, when irrigating only. On the discharge line of pump
install a line for filling fertilizer tank. Barrel or other open con-
tainer for fertilizer solution should be made of corrosion-resistant
-Main Discharge Line
I To Water Supply
Fig. 1. Equipment and arrangement necessary for injection of fertilizer
into a horizontal centrifugal pump.
materials (Fig. 1). A disadvantage of this method is that rates
of injection are often difficult to ascertain.
rDeep Well Turbine Pump
Main Discharge Line Sprinklers
W--l ~ Cut-off Valves
Casing I For
Container High Pressure
---Pipe for Emptying
Fertilizer I Container
Fig. 2. Equipment and arrangement necessary for injection of fertilizer
into the discharge line of a deep-well turbine pump, using an auxil-
iary driven motor and pump.
Auxiliary Displacement Pump: This type of injector can
be used with shallow or deep centrifugal pumping systems.
Since deep-well pumps do not exert suction in any part of the
system above ground, fertilizer solution must be introduced into
either the well or the discharge line. A common method, especi-
ally adapted where electric power is available, is use of a small
high pressure pump (stainless steel) to inject solution into the
The fertilizer injector pump must deliver a higher pressure
than the main discharge line. The injector should also be able to
deliver a small volume at a high head (3 to 3 gpm at 80-100 psi).
It may be electric or air-cooled gasoline engine driven (Fig. 2).
Another accepted and proven method of supplying power to
the small injection pump is to install a jack-shaft and drive it
through a separate clutch from the main irrigation power unit.
Gear and other type rotary pumps may be severely damaged
by the fertilizer solution. This is especially true for bronze or
Aspirator Pump: This type of injector can be used with
shallow or deep well centrifugal pumping systems. With this
method, a portion of the water discharged from the irrigation
pump is bypassed through an aspirator (an apparatus for pro-
ducing a movement of fluids by suction). This creates a suction
*Deep Well Turbine Pump
Tube to Aspirator
Fig. 3. Arrangement of equipment necessary for injecting fertilizer into
irrigation water when using an Aspirator unit.
that draws fertilizer solution into the line (Fig. 3) An open fer-
tilizer tank can be used.
Commercially available injection units which introduce fer-
tilizer directly into the irrigation discharge lines are made by a
number of manufacturers. Some typical examples are as follows:
V-Belt driven auxiliary positive displacement pump. The
injector illustrated in Figure 4 is powered with a one-half inch
V-belt from the drive shaft of the irrigation engine; therefore, it
is not necessary to either take water from the irrigation line nor
to obstruct the irrigation line in order to power the injector. Elec-
tric motor driven models are also available.
Figure 4. Fertilizer injector using an auxiliary positive displacement
pump to force materials into irrigation water.
This injector is equipped with a flow meter which is graduated
from 10-100 %. Calibrated charts are furnished with each unit so
the application rate can be set by adjusting only one ball valve
located at the top of the flow meter. This flow meter also serves
as a continuous application sight gauge. At any time, should
trouble develop and the fertilizer not applied as desired, the float
in the flow meter will automaticaPy register this event.
This unit will build pressures up to 175 psi; therefore, the
unit will inject into any pressure or non-pressure irrigation
system. The pump on this unit is designed to run at 1750 rpm.
The governor incorporated in the system automatically compen-
sates the changes in volume by passing the excess amount back
to the fertilizer tank.
Eighty mesh screens are furnished to filter foreign particles
out of the fertilizer being applied. A spring loaded two-way check
valve is also furnished, which is installed on the irrigation pipe to
prevent gravity flow of the fertilizer when the unit is not in op-
eration. It also prevents water from coming back through the
unit to the fertilizer tank when the unit is not in operation. Since
the injector is powered from the drive shaft of the irrigation
engine, there is no danger of loading the irrigation pipe with
chemicals when irrigation stops.
Water-motor powered auxiliary positive displacement pump.
-The injector shown in Figure 5 is driven by water pressure.
No motor or gas engines are required. There are no restrictions
or pressure drop in lines. Fertilizer injection rate is from 3 to
45 gallons per hour. The unit handles all liquid fertilizers, in-
Figure 5. Water-motor powered fertilizer injecting pump.
cluding phosphoric acid and suspensions or slurries. It will also
handle Eptam herbicide and Vapam soil fumigant. A model is
now available to handle the chlorinated hydrocarbon soil fumi-
The manufacturer suggests that line pressures of 35 to 150
psi function best with the injector. Also, the speed of the pump
increases or decreases with variations in flow of the main line,
therefore providing a constant ratio of fertilizer injection. The
fertilizers do not contact the power portion of the pump. Rate of
output is regulated through use of a simple throttle valve.
The new 1967 model embodies functional improvements to
make this a versatile unit.
Impeller driven auxiliary positive displacement pump. A
unit of this type is shown in figure six. It is a lightweight por-
table self-contained ratio-feeder. This injector is powered by the
flow of water in the irrigation line instead of a differential in pres-
sures. It operates in direct proportion to the water flow offering
ratio-feeding; stopping and starting automatically with the
water as it passes through the water motor. Since the water
motor stops when the flow in the line stops, the injector can not
load the irrigation lines with a high concentration of chemicals.
Figure 6. Injector pump driven by impeller located in irrigation pipe
The unit can be inserted directly into most irrigation systems
where flows are from 100 gpm to 800 gpm. A by-pass assembly
is available for permanent irrigation systems and large flow lines
running over 800 gpm. Pressure drop through HydroMotor is less
than 5 psi when working at full capacity, and it operates against
pressures up to 125 psi. Injection ratios from 1 part in 300 down
to 1 part in 10,000 may be easily set while unit is operating.
Figure 7. Injector with integrally mounted, water motor powered aux-
iliary positive displacement pump.
Integrally mounted, water motor powered auxiliary positive
displacement pump. This precision unit will proportion liquid
into the line at a rate that will not vary more than 5 percent
regardless of changes in water flow rate or pressure (Fig. 7).
The unit consists of a water motor direct-driven injector pump.
all water used is passed and metered through the water motor.
The positive action piston injector pumps handle the liquid fer-
tilizer. These units handle water at rates from 25 to 700 gpm
with a proportion range of 1:2000 to 1:800.
Positive displacement injector with gear reduction drive:
a unit of this type, shown in figure eight, has a range of output
from 8 oz. per hour to 36.4 gals. per hour on one model and up to
600 gallons per hour on other models. All pumps are made alike
and are accurate with 3% per hour of 1/2 of 1% per hour.
They are constructed of stainless steel and teflon, allowing one
to pump anything from sulphuric-acid to black strap molasses to
Figure 8. Side view of positive displacement injector with gear reduc-
all grades and mixtures of liquid, slurry and suspension mixed
fertilizers as well as all herbicides, pesticides and insecticides.
By using teflon packing, it can be run for an indefinite period
of time without any liquid in the pump and no damage will be
done. The pump is positive displacement and has a built-in pres-
sure spring to prevent any liquid from siphoning back into the
water stream, if zero pounds of pressure occurs.
The piston runs at 70 strokes per minute, based on a 1750 rpm
power supply which can be powered by electric motor, water
drive, V-belt drive from the drive shaft of the irrigation pump or
crankshaft pulley of the engine. The pump requires only 1/10 of
1 hp., so any power source is sufficient to operate the pump, and
at pressures of 0 to 2500 psi.
Operation and Maintenance
When the equipment is properly flushed out after each opera-
tion, there has been little evidence that the solutions are harm-
ful to either the pump, pipe or sprinklers; however, phosphoric
acid and superphosphate will cause excessive corrosion and
extreme caution must be taken. Plastic (PVC) pipe and sprinkler
may offer a better solution for corrosion problems.
In general it will take from 30 minutes to a number of hours
to inject the fertilizer solution, depending on the irrigation and
injection rate. After fertilizer injection, depending on the concen-
tration of fertilizer used, allow additional running time to flush
fertilizer from the system and to wash fertilizer from the plants.
When irrigation is to be done at the same time as fertiliza-
tion, the "fertigation" should be done at the beginning of the
application period or setting. Then, operate the irrigation system
for a period to wash fertilizer off plants in order to avoid burn.
The use of trade names in this publication is solely for the purpose of
providing specific information. The information given is supplied with the
understanding that no discrimination is intended and no endorsement by
the Florida Agricultural Extension Service is implied.
Acknowledgement is given to the following firms for their cooperation
in furnishing information for this booklet:
1. Inject-O-Meter Mfg. Co., Clovis New Mexico (Figure 4).
2. K. C. Mattson Co., Pasedena, California (Figure 5).
3. General Hydrodynamics, Inc., Chula Vista, California (Figure 6).
4. Smith Precision Products Co., South Pasadena, California,
5. Nor-Pak Division of North Plains Fertilizer and Chemical, Inc.,
representatives of the Hills-McCanna Co., Dumas, Texas (Fig-
This public document was promulgated at an annual cost
of $677.46, or 6/4 cents per copy to inform farmers how to
apply liquid fertilizers.
COOPERATIVE EXTENSION WORK IN AGRICULTURE AND HOME ECONOMICS
(Acts of May 8 and June 30, 1914)
Cooperative Extension Service, IFAS, University of Florida
and United States Department of Agriculture, Cooperating
Joe N. Busby, Dean