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Group Title: Bulletin
Title: Injection of chemicals into irrigation systems
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Permanent Link: http://ufdc.ufl.edu/UF00008538/00001
 Material Information
Title: Injection of chemicals into irrigation systems rates, volumes, and injection periods
Series Title: Bulletin
Physical Description: 12 p. : ; 28 cm.
Language: English
Creator: Clark, Gary A
Publisher: Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida
Place of Publication: Gainesville
Publication Date: 1990
 Subjects
Subject: Irrigation   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Includes bibliographical references (p. 12).
Statement of Responsibility: G.A. Clark ... et al..
General Note: "June 1990"--Cover.
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Bibliographic ID: UF00008538
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: ltqf - AAA6800
ltuf - AHG0549
oclc - 22232879
alephbibnum - 001547011

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June 1990
)~; June 1990


D 0 GUI M1TA2E


Bulletin 250


Injection of Chemicals Into Irrigation Systems:

Rates, Volumes, and Injection Periods

G.A. Clark, D.Z. Haman and F.S. Zazueta


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Florida Cooperative Extension Service
Institute of Food and Agricultural Sciences
University of Florida
John T. Woeste, Dean








Injection of Chemicals Into Irrigation Systems: Rates,
Volumes, and Injection Periods


G.A. Clark, A.G. Smajstrla, F.S. Zazueta, and D. Z. Haman*


Introduction

Irrigation systems can be used to transport
soluble chemicals to the crop. Depending on the
type of irrigation system, chemicals may be applied
to the root zone, the aerial part of the plant, or
both. The process of chemical transport using the
irrigation system is referred to as chemigation.
Specific terms may be used to refer to specialized
applications of chemigation, such as nematigation
and fertigation.
Irrigation systems designed or adapted for
chemigation require specialized equipment for the
injection of the chemical solution into the irrigation
system at a controlled rate. Several injection
methods are possible and are discussed in detail in
other publications (Nakayama and Bucks, 1986;
Smajstrla et al., 1987; and Yeager and Henley,
1987). The cost, accuracy, reliability, and longevity
of the equipment varies greatly among manufactur-
ers.
It is important to select adequate equipment,
maintain it regularly, and properly operate it to
insure a successful chemigation system. New
irrigation system designs must consider which
chemicals are to be injected while selecting the
system components to insure compatibility. Uni-
formity of chemical application cannot exceed that
of the irrigation system. Therefore, it is very
important to have a well designed and well main-
tained irrigation system to provide the greatest
potential for a high level of application uniformity.
When existing irrigation systems are to be adapted
for chemigation, they should be thoroughly exam-
ined for uniformity of application as well as com-
patibility of the chemicals to be injected with
existing components.
Water quality is another factor to consider in the
design or adaptation of an irrigation system for
chemigation. Some water supplies require chemi-
cal amendment to prevent bacterial growths or


chemical precipitants from clogging the system.
This publication will concentrate on the manage-
ment aspects of chemigation and how chemigation
influences other aspects of irrigation management.

Chemical Mixtures and Injections

Chemicals may be applied as a precisely man-
aged level of concentration or as a bulk mass of
chemical with possibly varying concentration
levels. Concentration management requires a
precise injection system and is more involved than
bulk injection. The injection system must be
specifically calibrated for the irrigation system it is
to be operated on and under the operating condi-
tions that will exist when chemicals are to be
injected. Variations in operating pressure, system
flow rate, and at times even temperature can
influence the calibration of the system. Bulk
injection simply involves the injection of a desired
volume or amount of chemical into the system. The
injection rate does not need to be precisely con-
trolled. However, it should not be damaging to any
part of the system or crop, should not exceed
manufacturers' recommended application rates,
and should apply the chemical in a time period
which does not result in over-irrigation or leaching
of previously applied chemicals.

Concentration Mixtures of a Stock Solution
Some chemical applications require that a
certain concentration level be maintained for
proper use of that chemical in that situation.
Concentrations are generally expressed in parts per
million (ppm), which is not a convenient term for
mixing purposes. Chemicals may be supplied in
dry form or liquid form; however, the end result is a
liquid mixture of a desired concentration. The
following equation can be used to determine the
mass of chemical required to achieve a particular
ppm level.


* Assistant Professor, Extension Irrigation Specialist, Gulf Coast Research and Education Center, Bradenton, FL;
Professor,Associate Professor and Assistant Professor, respectively, Agricultural Engineering Department; IFAS, Uni-
versity of Florida, Gainesville, FL.









desired ppm
lb of raw chemical per 100 gal = .(1)
1205

This provides the mass of actual chemical that
must be dissolved per 100 gallons of water. For
example, a 200 ppm concentration level of nitrogen
as a fertilizer solution will require:


200 ppm
--- = 0.17 lb. of N per 100 gal. of water.
1205


This is pounds of actual nitrogen required and
not pounds of fertilizer mix as either a dry or liquid
source.
Many chemicals are supplied as either a percent-
age by weight of a dry or liquid mixture. Therefore
the mass of chemical mixture required will depend
on the concentration of raw chemical in the mix-
ture. Equation (2) can be used to determine the
mass of chemical mixture required to provide the
necessary level of raw chemical.


(M)(100)
M(mixture) = (2)
%X


where M(mixture) = the required mass of
chemical mixture (lb.),
M = the desired mass of chemi-
Scal X (lb.), and
%X = the percentage of chemical
X in the mixture.

If in the above example a 16-4-8 (N-P205-K20)
dry fertilizer mix was used, then the required mass
of fertilizer mix for 100 gallons of solution would
be:


(0.17 pounds)(100)
= 1.1 pounds.
16%


Therefore 1.1 pounds of 16-4-8 fertilizer source
mix are required to supply 0.17 pounds of nitrogen.
Table 1 combines both Equations (1) and (2) to
provide the mass of chemical mixture (for example,
fertilizer mix) to add to 100 gallons of water to
obtain a certain ppm level for the desired chemical.


An example using Table 1 is included in the Ap-
pendix.
It is important to remember that the A-B-C
analysis of a fertilizer label refers to the nitrogen
(N), phosphorus oxide (P205), and potash (K20).
Therefore only 44% of the B factor (P 20) refers to
actual phosphorous (P), and only 83%of the C
factor (K20) refers to actual potassium (K). Equa-
tion (2) can be slightly rearranged to solve for M
based on M(mixture), and used to determine the
mass of actual P or K contained in a fertilizer mix.
For example, in 50 pounds of 16-4-8 fertilizer the
mass of P20 is


(50 pounds)(4%)
0 = 2.0 pounds of P20 .
100


Similarly, the mass of actual P would be



(2.0 pounds)(44%)
= 0.88 pounds of P.
100


Therefore 50 pounds of a 16-4-8 fertilizer mix-
ture contains only 0.88 pounds of actual P. The
same procedure can be used to determine that the
amount of actual K is 3.32 lbs.
When chemicals are supplied in liquid form, it is
more convenient to measure volumes rather than
masses or weights. This requires the specific
density or specific weight (S ) of the liquid mixture
such as pounds of chemical per gallon of liquid.
This property should be provided by the manufac-
turer or chemical supplier and can be used to
simply convert from required lbs. to required
gallons. For example a liquid fertilizer provided as
a 4-0-8 solution has 4% nitrogen by weight. How-
ever, the amount of nitrogen is not known unless
the specific weight of the chemical (fertilizer)
solution is known, such as 9.6 lb. per gallon. As
was previously mentioned, this value varies among
chemical mixtures and should be on the chemical
label, but may be obtained from the chemical
supplier.

Concentration Injection Rates
The previous section described the procedure for
mixing particular concentrations of a stock solu-
tion. However, many systems will have flowing
water with a requirement to maintain a desired
concentration of a chemical in that system. This







requires injecting a supply mixture at the proper
rate to maintain the desired concentration level.
The following equation or Tables 2 and 3 can be
used to determine the injection rate necessary to
maintain the desired concentration of a chemical X.


(ppmx) (Qw) (8.3)

[(%X)(Sx) (10000)] [(ppmx) (Sx)]


where Qi = Injection rate in gallons per minute
(gpm),
Q = Water supply flow rate (gpm),
83 = Specific weight of water (lb. /gal.),
ppm = Desired ppm level of chemical X,
%X = Percentage of chemical X in the
stock solution, and
Sx = Specific weight of the stock solution
mix (lb. /gal.).

For example, chlorine is to be injected to provide
10 ppm of free chlorine into a micro-irrigation
system which has a system flow rate of 550 gpm.
The chlorine stock solution contains 5% free chlo-
rine (sodium hypochlorite source, NaOC1) and has a
specific weight of 9.1 lbs. per gallon. Therefore,

Qw = 550; ppmx = 10; %X = 5; Sx = 9.1; and


(10) (550) (8.3)
i=[(5) (9.1) (10000 10) (9.
[(5) (9.1) (10000)] [(10) (9.1)1


= 0.100 gpm.


Therefore, the injector should be set to provide
0.10 gallons per minute of stock solution into the ir-
rigation system in order to maintain an injected
free chlorine level of 10 ppm. The actual ppm of
free chlorine throughout the system will depend on
how much free chlorine is used by organic in the
water supply and in the irrigation system.
If the specific weight of the chemical is close to
that of water, Equation (3) can be simpified. The
simplified approximation to Equation (3) is:


(ppmx) (Qw)
Qi = -- (4)
(%X) (10000)


where Qi = Injection rate in gallons per minute
(gpm),
Qw = Water supply flow rate (gpm),
ppmx = Desired ppm level of chemical X,
and
%X = Percentage of chemical X in the


stock solution.
In repeating the above chlorine example we get:


Q = 550 gpm; ppmx = 10; and %X = 5; and


(10)(550)
Qi= -----= 0.10 gpm
(5) (10000)


This result is consistent with the previous
example. In most cases, Equation (4) may be used.
However, if greater accuracy is needed, then use
Equation (3).
Some injectors are operated to inject on a gal-
lons-per-hour (gph) basis. Therefore, the injector
rate determined above must be converted using the
following equation:


Qi(gph) = (60) (Qi[gpm]).


For example, a flow rate of 0.10 gpm is equal to a
flow rate of 6.0 gph.

Injection Volumes and Periods

Chemical mixtures may be injected directly from
the stock supply tank or from an injector feeder
tank. Injector feeder tanks are useful for injecting
a specific volume of liquid, regardless of the injec-
tion rate. When the tank is empty the desired
volume of chemical mixture has been injected. This
procedure eliminates excess applications of chemi-
cals which may occur due to pump or controller
failure.
The size of the required feeder tank will depend
on the volume of chemical mixture to be injected,
which in turn will depend on either the total
amount or volume of chemical to be applied or on
the length of the injection period. Volumetric
applications can be based on area applications or
the sum of individual applications. For example, a
pesticide may require that X pounds of a chemical
be applied per acre; a vegetable grower may want
to apply a certain mass of fertilizer per acre or per
1000 bedded feet of plant row; or a citrus or nursery
operator may want to supply a certain amount of
fertilizer per irrigated plant. In addition to the
desired level of fertilization, these situations
require knowledge of the irrigated acreage per set,
total feet of bedded production area irrigated per
set, or the number of plants or trees irrigated in
each set.







Injection Volumes
To determine the required injection volume for
bulk applications, the mass of the desired chemical
or compound dissolved per gallon of stock solution
must be known. This can be determined by using
Table 4 or Equation (6) as follows:


(%X) (Sx)
Sm =
100


where S = Mass of chemical X per gallon of
stock solution (lb/gal),
%X = Percentage of chemical X in the
solution (%), and
S = Specific weight of the stock solution
(Ib/gal).

Then by knowing the mass of that chemical
contained per gallon of stock solution, the required
volume can be determined using Table 5 or the
following equation:


(Mx)
m


where V = Required mixture volume (gal),
M = Mass of chemical required (lb), and
S = Mass of chemical per gallon of
mixture, (lb/gal; from Table 4 or
Equation 6).

For example, a vegetable grower wishes to apply
4 lb. of N per 1000 bedded feet of plant row each
week; the N is to be applied in 3 applications per
week; 20 acres are to be irrigated per set; and the
system has 4500 bedded feet per acre. What size
feeder tank is necessary for injecting a 4-0-8 fertil-
izer solution which has a specific weight of 9.55 lb
per gallon?


The weekly production requirement of
total N is:
(20 acres) (4500 ft/acre) (4 lb of N/1000
feet) =
= 360 lb of N per week.
The application requirement of N (3 ap-
plications) is:
(360 lb of N per week) / (3 applications
per week) =
= 120 lbs of N per application.


Using Equation (6)

( 4 ) (9.55)
S = = 0.38 lb of N per gallon of solution.
100

The injection volume per application is (Equa-
tion 7):


120 lb of N per application


0.38 lb of N per gallon of solution.


= 316 gallons.


Therefore, the feeder tank must be at least 316
gallons to provide room for this fertilizer applica-
tion.
Sometimes chemicals are injected on a periodic
basis to maintain a certain injected concentration
of that chemical during that period. In this case,
the required injection volume of stock solution
depends on the length of the injection period, and
the injection rate. The required stock solution
volume can be determined from Equation (8) as
follows:


Vm (Q) (Ti)


where V = Required mixture injection volume
(gal),
Q = Injector flow rate (gpm), and
T = Injection period (minutes).

For example, a micro irrigation system manager
desires to inject 10 ppm of free chlorine into his
irrigation system for a period of 40 minutes. The
irrigation system delivers water at a rate of 550
gpm, the chlorine stock solution weighs 9.1 lbs. per
gallon and contains 5% of free chlorine. From a
previous example using Equation (3), the required
injector flow rate was 0.10 gpm. Therefore, the
required injection volume is:

V = (0.10 gpm) (40 minutes)
= 4 gallons of stock solution.


Therefore, only a small feeder tank is required
for this application.

Injection Periods and Calibration
The length of the injection cycle is important
from an irrigation management viewpoint. With
respect to the injection period, several criteria may
need to be addressed, such as the frequency of








chemical application (daily, semi-weekly, weekly,
etc.) and the maximum time allocated per irrigation
zone. For example, for daily chemical applications
the number of irrigation zones multiplied by the
injection period per zone cannot exceed 24 hours.
Furthermore, if the injection period exceeds the
maximum irrigation period which results in over-
irrigation and leaching, then split chemical applica-
tions are necessary.
The injection period is generally determined
from the volume of chemical to be applied and the
rate of injection. As was previously mentioned,
some chemical applications require that a specific
concentration be maintained for a particular
application or injection period. In this case the
injection period is already pre-set.
The injection volume was discussed in the
previous section. Injection rate may be provided by
the supplier of the injection system. However,
whether the injection rate is already available or
not, calibration is required. Calibration should be
performed on the irrigation system which is to be
used with the injection system. Also, because
irrigation system operating pressures and flow
characteristics may influence injection rates,
calibration should be performed while the irrigation
system is operating.
One simple calibration procedure involves
placing a flow meter on the injection line and then
measuring the volume of chemical injected in a
specific period. A measurement period of 2 to 5
minutes should suffice, however longer measure-
ment periods provide better results. Also, three or
more replications of the measurement should be
performed to obtain an accurate calibration and to
eliminate measurement error or discrepancies. The
quality of the flow meter will influence the quality
of the calibration. Therefore, use a good flow meter
sized to operate in the estimated flow range of the
injection system and manufactured for use with the
chemicals being injected. Corrosion of the flow
meter could alter the injection rate and possibly
result in damage to some other part of the irriga-
tion system. Also, be sure that the flow meter can
operate under the higher pressures associated with
some injectors.
A second calibration procedure involves physical
measurement of the injected volume during the
measurement period. This procedure can be
performed using one of two methods. In each
method a container is filled with a known volume of
the chemical to be injected. Water or colored water
may be substituted for the chemical but may not
provide accurate results with some injectors if the
viscosity is very different from that of the chemical.
The first method measures the time required to
inject all of the known chemical volume and then


uses the following formula to determine the injec-
tion rate


Qi "
T.
1


where Q. = Injection rate (gpm),
V. = Injected volume (gal), and
T. = Time required (min) to inject
volume V..


The second method measures the initial volume
and the final volume after a specified injection
period. The injection period should be at least
several minutes but short enough that all of the
chemical has not been injected. Calculation of the
injection rate is similar to the above procedure with
a slight modification of Equation (9) as follows:


V1-V2
Qi =--


(10)


where Q. = Injection rate (gpm),
Vi = Initial chemical volume (gal),
V2 = Final chemical volume (gal), and
T. = Injection measurement period
(min).

If a positive displacement type of pump is used,
the injected volume can be determined by counting
the number of piston strokes in the measurement
period and then multiplying the number of strokes
by the displacement volume per stroke. The
displacement volume per stroke should be meas-
ured periodically to insure proper operation.
Once the injection rate is known, the injection
period for any chemical volume can be determined
from rearranging Equation (9) as follows:


T. = --
SQi


(11)


where T. = Required injection period (min),
= Volume of chemical to be injected
(gal),and
Qi = Injection rate (gpm) of the system.

For example, the vegetable grower in the previ-
ous fertilizer example has a piston injection pump







which was measured to give 42 piston strokes in a
three-minute period. Each piston stroke of the
pump corresponds to 0.10 gallons. Therefore, the
injection rate is


(42 strokes) (0.10 gallons/stroke)


3 minutes


= 1.40 gpm


In the previous example the grower needed to
apply 316 gallons of fertilizer mix three times each
week. The required injection period for this volume
of fertilizer will be

316 gallons
T. = 225 minutes.
1.40 gpm


Therefore the system must be operated for about
225 minutes on each of the three fertilizer injection


days to apply the required level of fertilizer. If the
crop is shallow rooted and the soil is sandy, it may
be best to apply the fertilizer in three 75 minute
cycles (i.e. morning, mid-day and afternoon) to
avoid moving fertilizer out of the root zone of the
crop. If this injection schedule is a problem, it may
be better to inject fertilizer every day or upgrade
the capacity of the injection system to reduce the
total injection period.

Summary

Information pertaining to the injection of chemi-
cals into irrigation systems was discussed in terms
of concentration injections, bulk injections, quan-
tity of chemicals to be injected, injection system
calibration and injection periods. The information
was provided to assist irrigation system designers
and operators with the chemigation aspects of
irrigation system design, scheduling and manage-
ment.


Qi =








APPENDIX TABLES


Table 1. The mass (lb) of chemical mixture (i.e., fertilizer mix) to add to 100 gallons of water for different
ppm level solutions.


PPM PERCENT ANALYSIS OF THE MIXTURE
LEVEL
5 10 15 20 25 30 40 50


(lb per 100 gallons)

10 0.17 0.08 0.06 0.04 0.03 0.03 0.02 0.02
20 0.33 0.17 0.11 0.08 0.07 0.06 0.04 0.03
30 0.50 0.25 0.17 0.12 0.10 0.08 0.06 0.05
40 0.66 0.33 0.22 0.17 0.13 0.11 0.08 0.07
50 0.83 0.41 0.28 0.21 0.17 0.14 0.10 0.08
60 1.00 0.50 0.33 0.25 0.20 0.17 0.12 0.10
70 1.16 0.58 0.39 0.29 0.23 0.19 0.15 0.12
80 1.33 0.66 0.44 0.33 0.27 0.22 0.17 0.13
90 1.49 0.75 0.50 0.37 0.30 0.25 0.19 0.15
100 1.66 0.83 0.55 0.41 0.33 0.28 0.21 0.17
200 3.32 1.66 1.11 0.83 0.66 0.55 0.41 0.33
400 6.64 3.32 2.21 1.66 1.33 1.11 0.83 0.66
600 9.96 4.98 3.32 2.49 1.99 1.66 1.24 1.00
800 13.28 6.64 4.43 3.32 2.66 2.21 1.66 1.33
1000 16.60 8.30 5.53 4.15 3.32 2.77 2.07 1.66







Table 2. Chemical injection rate expressed in gpm of injection rate per 100 gpm of irrigation system flow
rate for different desired concentration levels (ppm) and different stock solution concentration levels.1


DESIRED PERCENT ANALYSIS OF THE CHEMICAL IN THE STOCK SOLUTION
PPM
LEVEL 4 8 12 16 20 30 40 50


(gpm of injection per 100 gpm of irrigation rate)

10 0.025 0.013 0.008 0.006 0.005 0.003 0.003 0.002
20 0.050 0.025 0.017 0.013 0.010 0.007 0.005 0.004
30 0.075 0.038 0.025 0.019 0.015 0.010 0.008 0.006
40 0.100 0.050 0.033 0.025 0.020 0.013 0.010 0.008
50 0.125 0.063 0.042 0.031 0.025 0.017 0.013 0.010
60 0.150 0.075 0.050 0.038 0.030 0.020 0.015 0.012
70 0.175 0.088 0.058 0.044 0.035 0.023 0.018 0.014
80 0.200 0.100 0.067 0.050 0.040 0.027 0.020 0.016
90 0.225 0.113 0.075 0.056 0.045 0.030 0.023 0.018
100 0.250 0.125 0.083 0.063 0.050 0.033 0.025 0.020
200 0.500 0.250 0.167 0.125 0.100 0.067 0.050 0.040
400 1.000 0.500 0.333 0.250 0.200 0.133 0.100 0.080
600 1.500 0.750 0.500 0.375 0.300 0.200 0.150 0.120
800 2.000 1.000 0.667 0.500 0.400 0.267 0.200 0.160
1000 2.500 1.250 0.833 0.625 0.500 0.333 0.250 0.200


(Caution: these values assume a stock solution specific weight equal to water. If necessary, these num-
bers may be adjusted by multiplying by the ratio of the specific weight of the chemical solution to the specific
weight of water.)








Table 3. Chemical injection rate expressed in gph of injection rate per 100 gpm of irrigation system flow rate
for different desired concentration levels (ppm) and different stock solution concentration levels.1


DESIRED PERCENT ANALYSIS OF THE CHEMICAL IN THE STOCK SOLUTION
PPM
LEVEL 4 8 12 16 20 30 40 50


(gph of injection per 100 gpm of irrigation rate)


10
20
30
40
50
60
70
80
90
100
200
400
600
800
1000


1.50
3.00
4.50
6.00
7.50
9.00
10.50
12.00
13.50
15.00
30.00
60.00
90.00
120.00
150.00


0.75
1.50
2.25
3.00
3.75
4.50
5.25
6.00
6.75
7.50
15.00
30.00
45.00
60.00
75.00


0.50
1.00
1.50
2.00
2.50
3.00
3.50
4.00
4.50
5.00
10.00
20.00
30.00
40.00
50.00


0.38
0.75
1.13
1.50
1.88
2.25
2.63
3.00
3.38
3.75
7.50
15.00
22.50
30.00
37.50


0.30
0.60
0.90
1.20
1.50
1.80
2.10
2.40
2.70
3.00
6.00
12.00
18.00
24.00
30.00


0.20
0.40
0.60
0.80
1.00
1.20
1.40
1.60
1.80
2.00
4.00
8.00
12.00
16.00
20.00


0.15
0.30
0.45
0.60
0.75
0.90
1.05
1.20
1.35
1.50
3.00
6.00
9.00
12.00
15.00


0.12
0.24
0.36
0.48
0.60
0.72
0.84
0.96
1.08
1.20
2.40
4.80
7.20
9.60
12.00


1(Caution: these values assume a stock solution specific weight equal to water. If necessary, these num-
bers may be adjusted by multiplying by the ratio of the specific weight of the chemical solution to the specific
weight of water.)







Table 4. The mass (lb) of active chemical contained per gallon of stock solution (Smx) for different
combinations of specific weight and chemical concentration.


SPECIFIC PERCENT CONCENTRATION OF THE ACTIVE CHEMICAL
WEIGHT
(lb/gal) 4 8 12 16 20 30 40 50


(lb of active chemical per gallon)

8.0 0.32 0.64 0.96 1.28 1.60 2.40 3.20 4.00
8.5 0.34 0.68 1.02 1.36 1.70 2.55 3.40 4.25
9.0 0.36 0.72 1.08 1.44 1.80 2.70 3.60 4.50
9.5 0.38 0.76 1.14 1.52 1.90 2.85 3.80 4.75
10.0 0.40 0.80 1.20 1.60 2.00 3.00 4.00 5.00
10.5 0.42 0.84 1.26 1.68 2.10 3.15 4.20 5.25
11.0 0.44 0.88 1.32 1.76 2.20 3.30 4.40 5.50
11.5 0.46 0.92 1.38 1.84 2.30 3.45 4.60 5.75








Table 5. Required volume (gal) of chemical mixture to provide a desired level of an active chemical for
different concentrations (lb/gal) of the chemical in the stock solution from Table 4.


MASS OF S
mx
CHEMICAL MASS OF CHEMICAL (lb) PER GALLON OF STOCK SOLUTION
DESIRED
(lb) 0.2 0.4 0.6 0.8 1.0 2.0 3.0 4.0


(gallons of stock solution)

20 100 50 33 25 20 10 7 5
40 200 100 67 50 40 20 13 10
60 300 150 100 75 60 30 20 15
80 400 200 133 100 80 40 27 20
100 500 250 167 125 100 50 33 25
150 750 375 250 188 150 75 50 38
200 1000 500 333 250 200 100 67 50
250 1250 625 417 313 250 125 83 63
300 1500 750 500 375 300 150 100 75
350 1750 875 583 438 350 175 117 88
400 2000 1000 667 500 400 200 133 100
450 2250 1125 750 563 450 225 150 113
500 2500 1250 833 625 500 250 167 125







TABLE EXAMPLES

1. How much 10-10-10 soluble fertilizer mix is
required to mix with water to make a 100 ppm
solution of actual nitrogen?
From Table 1 a value of 0.83 lb of soluble fertil-
izer is required per 100 gallons of water (solution)
to provide a 100 ppm solution of nitrogen.

2. Chlorine is to be injected into an irrigation
system which has a water delivery (supply) rate of
400 gpm. The chlorine stock solution contains 8 %
of "free" chlorine. What stock solution injection
rate is necessary to provide 20 ppm of "free" chlo-
rine to the irrigation supply water?
Table 2 (or Table 3) indicates that to provide a 20
ppm concentration level with an 8 % stock solution,
approximately 0.025 gpm (1.50 gph) of stock
solution injection is necessary per 100 gpm of water
delivery rate. Therefore, a 400 gpm water delivery
rate requires a stock solution injection rate of:


(0.025 gpm/100 gpm) (400 gpm) = 0.10 gpm.


(1.50 gph/100 gpm)(400 gpm) = 6.0 gph.


Therefore injecting an 8 % stock solution of chlo-
rine at 0.10 gpm (6.0 gph) into an irrigation system
with a system flow rate of 400 gpm will provide ap-
proximately 20 ppm of "free" chlorine into the
system.

3. A vegetable field is to be fertigated (have
fertilizer injected) on a weekly basis with three
pounds of nitrogen (N) per 1000 feet of plant bed
per week. The field is 25 acres in area with 6000
bedded feet per acre. What size of feeder tank is
necessary to hold the required volume of fertilizer
mixture if the mixture is a 4-0-8 solution with a
specific weight of 10 lb/gal?

The required amount of fertilizer is:

= (3 lb/1000 ft) (6000 ft/acre) = 18 lb/acre

= (18 lb/acre) (25 acres)

= 450 lb of N per week.

Table 4 is used to determine the amount of
chemical (nitrogen) per gallon of solution. A 4-0-8
solution of fertilizer (Sx = 10) has 4 % nitrogen.

From Table 4 read the actual amount of N as 0.40
lb per gallon of solution.


Next use Table 5 to determine the required
volume of mixture. For a 0.40 lb/gal chemical
(nitrogen) density and 450 lb requirement, read
1125 gallons of fertilizer mixture required. There-
fore, the supply tank must have a minimum capac-
ity of 1125 gallons to hold the weekly supply of
fertilizer.

References

Ingram, D., and B. Hoadley. 1986. Chemical
Injection for Drip Irrigation in the Woody Or-
namental Nursery. Ornamental Horticulture
Commercial Fact Sheet OHC-6. IFAS, Univ.
of Florida, Gainesville, FL.

Kovach, S.P. 1984. Injection of Fertilizers into Drip
Irrigation Systems for Vegetables. IFAS
Circular 606, Univ. of Florida, Gainesville, FL.

Nakayama, F.S., and D.A. Bucks. 1986. Trickle
Irrigation for Crop Production: Design, Opera-
tion, and Management. Elsevier. Amsterdam.
383 p.

Smajstrla, A.G., D.S. Harrison, W.J. Becker, F.S.
Zazueta, and D.Z. Haman. 1985. Backflow
Prevention Requirements for Florida Irriga-
tion Systems. Bulletin 217. IFAS, Univ. of
Florida, Gainesville, FL.

Smajstrla, A.G., D.Z. Haman, and F.S. Zazueta.
1986. Chemical Injection (Chemigation):
Methods and Calibration. Agric. Engr. Ext.
Report 85-22 (revised). IFAS, Univ. of Florida,
Gainesville, FL.

Yeager, T.H. 1986. Fertigation Management for the
Wholesale Container Nursery. IFAS Bulletin
231. Univ. of Florida, Gainesville, FL.

Yeager, T.H. and R.W. Henley. 1987. Techniques of
Diluting Solution Fertilizers in Commercial
Nurseries and Greenhouses. IFAS Circular
695. Univ. of Florida, Gainesville, FL.



























































This publication was produced at a cost of $816.50, or 33.0 cents per copy to provide information about
injection of chemicals into irrigation systems: rates, volumes, and injection periods. 06-2500-90

COOPERATIVE EXTENSION SERVICE, UNIVERSITY OF FLORIDA, INSTITUTE OF FOOD AND AGRICULTURAL SCIENCES, John T.
Woeste, Director, in cooperation with the United States Department of Agriculture, publishes this information to further the purpose of the May 8
and June 30, 1914 Acts of Congress; and is authorized to provide research, educational information and other services only to individuals and
institutions that function without regard to race, color, sex, age, handicap or national origin. Single copies of extension publications (excluding 4-
H and youth publications) are available free to Florida residents from county extension offices. Information on bulk rates or copies for out-of-state
purchasers is available from C.M. Hinton, Publications Distribution Center, IFAS Building 664, University of Florida, Gainesville, Florida 32611.
Before publicizing this publication, editors should contact this address to determine availability.


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