Citation
Design of agricultural irrigation systems in Florida

Material Information

Title:
Design of agricultural irrigation systems in Florida
Series Title:
Florida Cooperative Extension Service bulletin 294
Creator:
Smajstrla, A. G. (Allen George)
Clark, G. A.
Haman, Dorota Z.
Zazueta, Fedro S.
Affiliation:
University of Florida -- Florida Cooperative Extension Service -- Institute of Food and Agricultural Sciences
Place of Publication:
Gainesville, Fla.
Publisher:
Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida
Publication Date:
Language:
English
Physical Description:
14 p. ; 28 cm.

Subjects

Subjects / Keywords:
Agriculture ( LCSH )
Farm life ( LCSH )
Farming ( LCSH )
University of Florida. ( LCSH )
Agriculture -- Florida ( LCSH )
Farm life -- Florida ( LCSH )
Irrigation -- Equipment and supplies -- Florida ( LCSH )
Irrigation engineering -- Florida ( LCSH )
Spatial Coverage:
North America -- United States of America -- Florida

Notes

Funding:
Florida Historical Agriculture and Rural Life

Record Information

Source Institution:
Marston Science Library, George A. Smathers Libraries, University of Florida
Holding Location:
Florida Agricultural Experiment Station, Florida Cooperative Extension Service, Florida Department of Agriculture and Consumer Services, and the Engineering and Industrial Experiment Station; Institute for Food and Agricultural Services (IFAS), University of Florida
Rights Management:
All rights reserved, Board of Trustees of the University of Florida
Resource Identifier:
30691237 ( OCLC )
AKA2278 ( NOTIS )
026328064 ( ALEPH )

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not reflect current scientific knowledge
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Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
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(EDIS)

site maintained by the Florida
Cooperative Extension Service.






Copyright 2005, Board of Trustees, University
of Florida




/o/


'UNIVERSITY OF

..,FLORIDA


Florida Cooperative Extension Service


Design of Agricultural Irrigation Systems in Florida'
A.G. Smajstrla, G.A. Clark, D.Z. Haman and F.S. Zazueta2


INTRODUCTION

Over two million acres of agricultural crops are
irrigated in Florida. See IFAS Ext. Cir. 1030 (56) and
Bul. 276 (39). This large acreage requires irrigation
despite Florida's high annual rainfall because 1)
typical sandy soils have low water-holding capacities;
2) rainfall is not uniformly distributed throughout the
year; 3) many high-value specialty crops are grown
and higher economic returns can be obtained by
avoiding water stress; and 4) irrigation systems are
extensively used for environmental modification,
including freeze protection and .crop cooling. See
IFAS Ext. Cir. 940 (9).

Many different types of irrigation systems are
used in Florida. Many different systems are required
because of the great variety of crops, the relative
availability of water, diverse hydrological conditions,
variable soil characteristics, and ranges in system
costs. Also, all irrigation systems are not adaptable to
all types of crops and crop production systems. See
IFAS Ext. Cir. 821 (34) and Cir. 1035 (44). In
Florida, irrigation systems are used to provide water
for crop evapotranspiration (ET), but also for many
other purposes as well, such as freeze protection and
crop cooling if required in a specific production
system. See IFAS Ext. Cir. 940, Uses of Water in
Florida Crop Production Systems (9).

The objective of irrigation system design is to
develop a system of irrigation components that is


capable of applying water (and often chemicals) in an
efficient and timely manner in order to optimize crop
production. Efficiency is defined broadly here to
consider economic, labor, management, and
production system constraints, as well as conservation
of natural resources. See IFAS Ext. Bul. 247 (40).
Timeliness refers to system capabilities which enable
irrigations to be applied when required and in the
amounts required to optimize crop production. See
IFAS Ext. Bul. 249 (43). General irrigation
terminology and terms related to irrigation in Florida
are defined in Agricultural Engineering Fact Sheets
AE-66, Basic Irigation Terminology (32) and AE-45,
Glossary of Trickle Inigation Terms (71).

Design of irrigation systems specifies individual
components and the conditions under which they will
be operated. This includes the types of components
required, their sizes, and other characteristics such as
pressure ratings, resistance to chemicals to be
injected, etc. Failure to consider all of these factors
may result in the design of an inefficient irrigation
system or system failure. For more information on
the consequences of poor design, see Ag. Eng. Fact
Sheet AE-73, Potential Impacts of Improper Irrigation
System Design (63).

Standards for. irrigation system design in Florida
have been developed by three agencies: American
Society of Agricultural Engineers (ASAE); Soil
Conservation Service (SCS); and Florida Irrigation
Society (FIS). Complete references to these


1. This document is Bulletin 294, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida.
Publication date: March 1994.
2. A.G. Smajstrla, Professor, Agricultural Engineering Department; G.A. Clark, Associate Professor, Gulf Coast Research and Education Center,
Brandenton, FL; D.Z. Haman, Associate Professor, and F.S. Zazueta, Professor, Agricultural Engineering Department, Cooperative Extension
Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville FL 32611.
The Institute of Food and Agricultural Sciences Is an equal opportunity/affirmative action employer 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. For Information on obtaining other extension publications, contact your county Cooperative Extension Service office.
Florida Cooperative Extension Service / Institute of Food and Agricultural Sciences / University of Florida / John T. Woeste, Dean


Bulletin 294
March 1994


el FO',!,1






Design of Agricultural Irrigation Systems in Florida

standards are included in the list of references in this
publication (1, 12, 13, 36). Copies of these standards
are available from the developing agency.

Computer software has been developed by the
University of Florida to help with the design and
management of Florida irrigation systems. Water
management utilities were published by Zazueta et al.
(69) and continue to be developed. A complete list
of available software is published in the IFAS
Microcomputer Software Catalog (64).

Major components of irrigation systems must
often be designed in groups for compatibility and
efficiency. This publication discusses the major
component groups of 1) control equipment; 2) water
conveyance system; 3) water distribution system; and
4) pumping system. Selection of operating conditions
(flow rates and pressures) is also discussed. This
publication references many other publications which
provide more information on specific aspects of
irrigation system design in Florida.

SYSTEM COMPONENT GROUPS

Control Equipment

The objective of control equipment design is to
specify components that will enable the irrigation
system to be efficiently and safely managed and
monitored in order to optimize crop production,
conserve water and preserve water quality. Control
equipment consists of the components required to
regulate and monitor water and chemical applications
to an irrigation system, and safety equipment required
to protect the water supply from contamination.
These include valves, pressure regulators, flow
meters, backflow prevention systems, filters, pressure
gauges, chemical injection equipment, and irrigation
controllers.

Valves

Valves are required to control the filling of
irrigation systems at pump startup, to control flows to
the desired subunits of a system, and to allow flushing
of irrigation pipes. Only properly pressure-rated
irrigation valves must be used to avoid failures due to
system pressure and hydraulic shock (water hammer)
problems. Valve materials and components must be
resistent to corrosion by the irrigation water and any
chemicals injected during irrigation. I o I


SC IECE
LIBRARY


Page 2


Valves must be properly sized to avoid excessive
pressure losses. Normally, valves should be the same
size as the pipeline in which they are installed.
Installing smaller valves to save initial costs will result
in higher operating costs for the life of the system due
to friction losses.

Automatically-controlled irrigation systems will
require the use of automatic valves. These may be
controlled by electric solenoids or hydraulic pressures,
depending upon the type of timer/controller used.
Like manual valves, automatic valves should be
selected based on friction loss and water hammer
considerations.

For more information on valve types and
selection, see IFAS Ext. Cir. 824, Valves in Irrigation
Systems (19). For information on estimating and
controlling hydraulic shock, see IFAS Ext. Cir. 828,
Water Hammer in Irigation Systems (7).

Pressure Regulators
Pressure regulators may be required to maintain
the desired operating pressure in pipe flow systems.
These valves are required when it is necessary to
manage changing pumping conditions such as those
due to changes in the water source or flow
requirements to subunits of the irrigation system.
Regulators are also required if some subsections of a
system operate at different pressures than others.

Pressure regulators are often installed at either
the irrigation pump outlet, the entrances to subunits,
or at both locations. Pressure regulators may include
slow opening and check valve features. The slow
opening feature will allow an irrigation system to fill
slowly upon pump startup, thus avoiding water
hammer problems. The check valve feature will help
to prevent backflow to the water source, thus helping
to protect the water supply from contamination.

Because of their cost and the pressure losses
which occur through them, pressure regulators should
be used only when absolutely necessary. The system
subunits should be designed to have as nearly the
same pressure and flow rate requirements as possible
to minimize the number of regulators. In some cases,
field sizes, layouts, or slopes will not permit the same
flow rate and pressure to be used for all subunits.
Then, pressure regulators will be necessary. For
more information on pressure regulating valves, see
IFAS Ext. Cir. 824, Valves in Irigation Systems (19).






Design of Agricultural Irrigation Systems in Florida

Flow Meters

Flow (water) meters are required to properly
manage irrigation systems, specifically to measure the
amount of water applied at each irrigation. Meters
may be located at the irrigation pump to total the
water applications to the entire area irrigated, or they
may be located at field subunits to accurately monitor
applications to each individual subunit. Flow meters
are also required to continuously monitor irrigation
pumping efficiency, to indicate clogging problems
when decreasing flow rates are measured, and to
allow chemical injections to be accurately made when
chemical concentrations in the irrigation water are
important.

For more information on selection and
applications of flow meters, see IAS Ext. Bul. 207,
Agricultural Water Measurement (58) and Ag. Eng.
Fact Sheet AE-156, Measuring Irrigation Water (38).
For information on the applications of specific types
of flow meters, see the following IFAS Ag. Eng. Fact
Sheets: AE-18, Selection and Use of Impeller Meters for
Inigation Water Measurement (50); AE-22, Orifice
Meters for Water Flow Measurement (48); AE-25, Weirs
for Open-Channel Flow Measurement (47); and AE-
155, Shunt Flow Meters for Inigation Water
Measurement (37).

Backflow Prevention System

Florida law requires that a backflow prevention
system be installed on most irrigation systems.
Backflow prevention systems are always required
when 1) chemicals are injected into an irrigation
system, or 2) a public (municipal) water supply is
used, whether or not chemicals are injected.

Check all applicable local, county, or municipal
codes to determine the type of backflow prevention
device required for public water supplies. Use a
reduced-pressure zone backflow prevention device or
an air-gap separation of the irrigation system from the
water supply when chemicals are injected into
irrigation systems that are connected to municipal
water supplies.

No backflow prevention assembly is required if
the water supply is not a public water supply (for
example, if the water supply is an irrigation well, lake
or canal) if no chemicals are injected into the
irrigation system.


Page 3


When the water supply is not a public water
supply, the minimum backflow prevention system
requires a check valve, low pressure drain, and
vacuum breaker on the irrigation pipe to prevent
water and chemicals from flowing back to the water
source. It also requires interlocked power supplies to
prevent chemical injection unless the irrigation water
is flowing, a check valve on the injection line to
prevent water flow to the chemical supply tank, and
a positive shutoff valve on the chemical tank to
prevent accidental drainage from the tank.

When Chemical Toxicity Category I pesticides are
injected into irrigation systems and the water source
is not a public water supply, a double check valve, low
pressure drain, and vacuum relief valve assembly is
required. These pesticides are marked with the
keywords Danger or Poison on the label. When these
pesticides are injected, 1) either reduced pressure
principle backflow prevention devices or air-gap
separations are required when a public (municipal)
water supply is used; 2) only piston or diaphragm
types of injection pumps are permitted for injection;
and 3) pressure switches are required to shut off the
injection pump when the irrigation system pressure
drops to the point that uniformity of water application
is affected.

The Environmental Protection Agency (EPA)
requires that all pesticide products be labeled to
clearly state whether injection into irrigation systems
is permitted. Pesticide labels must also list the
backflow prevention equipment requirements and
application instructions. For more information on the
Florida backflow prevention law and equipment
requirements, see IFAS Ext. Bul. 217, Florida
Backflow Prevention Requirements for Agricultural
Irrigation Systems (52).

Filters

Almost without exception filters are required to
prevent clogging of microirrigation systems. Filters
remove small particles that may clog the tiny orifices
in emitters. The type of filtration system required
depends on the type of emitter used and the source
and quality of the irrigation water. Filters should be
selected based on emitter manufacturer's
recommendations.

If manufacturer's recommendations are not
available, use the equivalent of a 200 mesh screen
filter for drip systems. A larger mesh (coarser
screen) is normally acceptable for spray emitters,






Design of Agricultural Irrigation Systems in Florida

depending on the emitter orifice size. An 80 mesh
screen is commonly used for many spray emitters.
The mesh size selected should be small enough to
remove all particles larger than 1/4 the size of the
emitter orifice. For more information on selection
and use of screen filters, see Ag. Eng. Fact Sheet AE-
61, Screen Filters in Trickle Irrigation Systems (25).

If organic matter is a problem when pumping
from surface waters, media (sand) filters should be
used as the primary filter, with a secondary screen
filter. A strainer should be used on the pump intake
to exclude as much organic matter as possible. Also,
the intake should be positioned below the water
surface to avoid floating debris, and above the bottom
to avoid pumping sediment from the bottom of the
pond or canal. Self-cleaning strainers for the pump
inlet are available to prevent larger particles from
entering the irrigation system.

When pumping from wells, screen filters alone
are normally adequate unless large amounts of sand
are being pumped. If large amounts of sand are
being pumped, a vortex-type sand separator may be
used, followed by a screen filter. Settling basins may
also be used to remove large amounts of sand, but
basins may cause problems if organic matter such as
algae is present in the basins.

For more information on the design of settling
basins, see Ag. Eng. Fact Sheet AE-65, Settling Basins
for Trickle Irigation in Florida (23). For more
information on selection and applications of media
filters, see Ag. Eng. Fact Sheet AE-57, Media Filters
for Trickle Inigation in Florida (22).

Pressure losses occur through all filters. These
losses must be considered when an irrigation system
is designed. Also, the pressure losses increase as the
filter begins to clog. To operate properly, a filter
must be cleaned periodically to maintain its
effectiveness and to maintain pressure losses within
acceptable limits. Cleaning can be done manually or
by automatically backflushing the filter. Automatic
backflushing can be based on a timer or on the
increase in pressure loss across the filter that occurs
as it begins to clog. The pressure loss method is
preferred because it avoids unnecessary flushing when
the filter is not clogged, yet also avoids large pressure
losses through the filter.

The size and number of filters required depend
on the irrigation water quality, the size of the smallest
particle to be filtered, and on the flow rate. Filter


Page 4


manufacturer's recommendations should be followed
for sizing filters and for selecting the number of filters
required for the specific water quality and flow rate.
If clogging occurs too frequently, additional filters
should be added in parallel, so that each filters a
portion of the water. Also, adding more filters or
larger filters, so that the velocity of flow through each
filter is reduced, will improve the filtration
effectiveness.

Filtration may not be required when irrigation
systems other than microirrigation systems are used.
Y-strainers are often required on sprinkler systems to
prevent flakes of limerock from plugging sprinkler
nozzles when the Floridan aquifer is the source of
irrigation water. Also, coarse strainers are often used
on intakes of pumping systems to prevent debris from
fouling or damaging pumps. Otherwise, filters are
typically not required for sprinkler, surface, or
seepage irrigation systems.

Pressure Gauges
Functioning pressure gauges are required to
properly monitor the operation of pressurized
irrigation systems. A minimum of one gauge at the
pump discharge and one at each field subunit are
required. When filters are used, two gauges, one on
each side of the filter system, are required near the
pump.

Pressure gauges allow quick checks of the
irrigation system to be made. They allow the
operator to check that the system is operating at the
correct pressure, and therefore that the proper
average amount of water can potentially be applied.
Together with flow meters, pressure gauges also help
detect leaks in pipelines or clogged emitters, and they
provide a means of monitoring pumping efficiency.

Chemical Injection Equipment

Pressurized irrigation systems are often used to
apply chemicals, especially fertilizers. Growers can
obtain yield increases and minimize leaching losses
(and pollution) by injecting nutrients and other
chemicals through the irrigation systems. Many
growers currently inject fertilizer through sprinkler
and microirrigation systems. Chemical injection
equipment is required to add the correct amount and
rate of chemical. See IFAS Ext. Bul. 250 (4), Bul.
258 (33), Cir. 1033 (46) and Cir. 1039 (6).






Design of Agricultural Irrigation Systems in Florida

Several types of chemical injectors are
commercially available. These range from the low
cost venturi devices and devices that inject on the
suction side of centrifugal irrigation pumps to high
cost diaphragm- or piston-type positive displacement
pumps. The venturi and suction-side injection devices
have the advantage of low cost. It is not possible to
obtain a high degree of accuracy of injection rates
with these devices, but sufficient accuracy can be
obtained for injection of fertilizers where the total
volume rather than the rate of injection is of primary
concern. For more information on the types of
chemical injectors available, see IFAS Ext. Cir. 864,
Chemical Injection Methods for Irrigation (26).

If a high degree of precision is required such as
during injection, pesticides that would be detrimental
in other than known low concentrations, more precise
injection methods must be used. These include the
high precision but more costly positive displacement
injection pumps such as diaphragm and piston type
pumps. For more information on selection and
applications of these high precision pumps, see IFAS
Ext. Cir. 826, Positive Displacement Pumps for
Agricultural Applications (16).

Microirrigation systems typically require injection
of chemicals to prevent emitter plugging. See IFAS
Ext. Bul. 258, Causes and Prevention of Emitter
Plugging in Microinigation Systems (33) and SS-AGE-
805, Water Quality Problems Affecting Microinigation in
Florida (24). Microirrigation systems require high
precision chemical injection pumps to precisely
control biocides and water amendments used to
prevent emitter plugging.

Irrigation Controllers

Irrigation controllers are devices which
automatically turn the irrigation system and associated
equipment such as chemical injection pumps on and
off. Controllers are not mandatory for system
operation, but they are time- and labor-saving devices.
They are especially economical and efficient for
management of microirrigation systems on Florida's
sandy soils because of the requirement for frequent
irrigations.

Controllers range in capabilities from simple
timers which can turn a single valve on and off at pre-
set times to complex computer controllers. Computer
controllers are very complex systems that are
programmable and have microcomputer capabilities.
They can collect data from sensors, make calculations,


Page 5


and adjust water and chemical application schedules
in response to plant needs.

Irrigation timers use clocks to turn irrigation
systems on and off at pre-set times. This is done by
switch closures at pre-set times to open and close
solenoid valves and start or stop pump operations.
Irrigation controllers can provide other functions
besides those of a simple timer, including starting
irrigations based on soil moisture sensors or climate
factors, chemical injection control, recording times
and amounts of water applied to each zone, sensing
system problems and interrupting system operation
due to low pressure or low flow rates.

Controller prices range from less than $50 for
simple single-station timers to several thousand
dollars for the more complex programmable
controllers. Selection should be based on controller,
water, and labor costs, the irrigation system
complexity, and the number of tasks that are to be
automated.

Understanding of irrigation scheduling is
necessary to assess controller needs. For general
information on scheduling irrigations in Florida, see
IFAS Ext. Bul. 249, Basic Irigation Scheduling (43),
Bul. 254, Irrigation Scheduling with Evaporation Pans
(60), Cir. 487, Tensiometers for Soil Moisture
Measurement and Irrigation Scheduling (54), and Cir.
532, Measurement of Soil Water for Irrigation
Management (49).

For information on specific crops and production
systems, refer to the appropriate crop production
guides or crop-specific publications. For example, for
citrus, see Bul. 208, Trickle Irrigation Scheduling for
Florida Citrus (59); for microirrigation of row crops,
see Fact Sheet AE-72, Microirigation in Mulched Bed
Production Systems: Irrigation Depths (3); for
microirrigation of tomatoes, see Cir. 872, Irrigation
Scheduling and Management of Micro-inigated
Tomatoes (5). Other publications on specific crop
production systems are included in the list of
references to this publication.

For more information on irrigation controllers,
see IFAS Ext. Cir. 670, Computer Control of Mist
Systems for Nursery Propagation Houses (70), Cir. 688,
Control +:A Computer Controller forIrrigation Systems
(66), Cir. 705, IR-CONTROL: A Computer Controller
for Irrigation Systems (67), and Zazueta and Smajstrla,
Microcomputer-Based Control of Irrigation Systems
(68).






Design of Agricultural Irrigation Systems in Florida

Water Conveyance System
Water is conveyed from the pumping system to
the distribution system in open ditches or pipelines.
Ditches may be used for low-pressure (gravity-flow)
systems such as flood or seepage systems, when
permitted by topography, as in Florida flatwoods soil
areas. When pressurized irrigation systems are used,
water (and pressure) must be conveyed in pipelines.
Water is typically not conveyed in pipelines when
open ditches can be used because pipelines are much
more expensive than ditches, especially for large flow
rates.

Ditches may be either lined or unlined. Pipelines
may be permanent or temporary (portable). The
criteria for design of water conveyance systems are
primarily economic, and include an analysis of the life
expectancy of the conveyance system. The system
that conveys the required flow rate at the lowest cost
with the required life expectancy is normally chosen.

Open Ditches

Open ditches are used where water losses from
the ditches are small or when the cost per unit of
water is low. Losses occur due to deep percolation
and evaporation (or ET). Lined ditches are used
when deep percolation losses are large but
evaporation losses are relatively small. Ditch liners
may be concrete or plastic.

Ditch liners are not typically used in Florida
because open ditch systems are used only in soils with
restrictive layers or high water tables, both of which
minimize deep percolation losses. Also, the cost of
pumping water in Florida is relatively low. Open
ditches are used in flood and seepage irrigation
systems in Florida. However, many open ditches have
been replaced with pipelines in semi-closed seepage
systems to improve irrigation efficiency.

Pipelines

The mainline pipe in an irrigation system carries
water from its source (normally at the pump
discharge) to the field subunits where water is
distributed to the crop. Conveyance losses are
eliminated when pipelines are used. However, the
cost per unit of water delivered favors the use of
pipelines only when conveyance losses would
otherwise be large, the cost of conveyance losses
would exceed the pipeline cost, or pressurized
irrigation systems are used.


Page 6


There are several considerations in mainline pipe
design: a) pipe materials; b) potential water hammer
problems; c) pressure rating; and d) cost.

Pipe Materials

The preferred mainline pipe for permanent
irrigation systems is poly-vinylchloride (PVC) for
several reasons:

* low cost

* easy installation using either gasketed or glued
fittings

compatibility with chemicals typically injected into
irrigation systems

resistance to rust or corrosion, so that emitter
clogging from this source is not a problem

long life expectancy (approximately 40 years)
when properly buried and protected against
crushing by overburden pressures such as the
weight of heavy vehicles.

PVC mainline and submain pipes are normally
buried when permanently installed, because burying
will greatly extend the useful life of the pipe. If PVC
is not buried, it should be painted to protect it from
the sun.

Steel pipe should be used near the pumping and
control systems where pipes will be exposed to solar
radiation and where extra strength is required because
of the hydraulic shocks associated with pump startups.
Steel pipe should be used under roadways where extra
strength is required, or the PVC pipe should be
placed within a sleeve (typically corrugated steel is
used). Steel pipe is normally too expensive to use as
mainlines for irrigation systems and PVC is a better
alternative.

Aluminum pipe is primarily applicable only to
portable systems where the pipe will be left on the
surface. Uncoated aluminum pipe should never be
buried because it will rapidly deteriorate in Florida's
acid soils.












'BATTERY


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flow measurement.




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Figure 2. Price current meter for stream velocity measm




THE WATER BALANCE OF A FIELD


EVAPOTRANSPIRATION


LOSSES


1. Water balance components of an irrigated field.


RUNOFF

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WATER STORAGE
BOTTOM OF ROOT ZONE
7, DEEP
PERCOLATION
(DRAINAGE)






Design of Agricultural Irrigation Systems.in Florida

Water Hammer

To avoid water hammer problems in pipelines,
water velocity should be kept low, normally less than
5 feet per second (fps) for other than experienced
irrigation system designers. Under no conditions
should velocities ever exceed 10 fps. Velocities in the
range of 5 to 10 fps are sometimes used if:

* it is economical when both fixed and operating
costs are considered

pipe is properly pressure rated

startup velocities are controlled by slow-opening
valves

thrust blocks are installed as required at tees,
elbows, valves, or other points where hydraulic
shocks may occur

air relief valves are installed at all high points
along the pipeline as required

valves at the irrigation system subunits are not
normally all closed at pump startup.

For more information on water hammer, see
IFAS Ext. Cir. 828, Water Hammer in Irrigation
Systems (7).

Pressure Rating

Mainline pipe must be properly pressure rated to
withstand the normal system operating pressure plus
that due to hydraulic surges (water hammer). Also,
the pressure due to surges should normally not be
allowed to exceed 28% of the pipe pressure rating.

Class 160 (160 psi pressure rated, or SDR 26) is
normally adequately pressure-rated when velocities
are kept below 5 feet per second (fps). Higher
pressure ratings may be required if higher velocities
are used.

Cost

Mainline pipe sizes should be selected based on
cost and the previously discussed water hammer
considerations. The cost of the energy consumed by
friction losses should not exceed the amortized cost of
the next larger-sized pipe. The economic analysis
should consider the additional pumping costs
associated with smaller pipe sizes, fuel cost escalation


Page 7


for the life of the system, as well as any anticipated
expansions of the system that would require greater
flow rates in existing mainline pipes.

Friction loss tables that are used to estimate
pressure losses for the selection of mainline pipes
assume that the pipes flow full. Air relief valves
should be installed at all high points along the pipes
to ensure that air will not be trapped at these points,
causing the pipes to flow less than full. Trapped air
may also lead to water hammer problems when the
air is suddenly displaced.

For more information on irrigation pipelines, see
the appropriate ASAE, FIS and SCS standards. Also,
see Agricultural Engineering Fact Sheet AE-69,
Fittings and Connections for Flexible Polyethylene Pipe
Used in Microinigation Systems (14).

Irrigation Distribution Systems

Irrigation distribution systems are those
components of irrigation systems which apply water to
the irrigated areas. In seepage and flood irrigation
systems, these are the lateral ditches or pipes that
distribute water throughout the fields. In pressurized
systems, these are the system subunits or zones.
Subunits are the groups of emitters and lateral and
manifold pipelines that operate at the same time.

Subunit design criteria are 1) uniformity of water
application; and 2) economic considerations. Lateral
ditches and pipes must be large enough and spaced
closely enough that water is applied uniformly, but
ditches and pipes must be small enough and widely
enough spaced to be affordable. Absolute (100%)
uniformity is impossible. Extremely high uniformities
are costly. Tradeoffs of benefits from uniformities
versus cost must be made. For more information on
uniformity, see Agricultural Engineering Fact Sheet
AE-43 (65), and Bulletins 256 (2), 265 (41) and 266
(42). For more information on system costs, see
IFAS Ext. Cir. 821 (34), Bul. 276 (39), and Fact
Sheets AE-30 (53) and AE-74 (35).

Pressurized (Sprinkler and Microirrigation)
Systems

Pressure is normally regulated at the entrance to
a subunit, especially for large field-scale systems.
Control components located here are normally a valve
(manual or automatic), pressure regulator, pressure
gauge, and, for microirrigation systems, sometimes a
secondary (screen) filter.






Design of Agricultural Irrigation Systems in Florida

For sprinkler irrigation systems, high uniformity
is achieved by designing pipelines so that the variation
in flow rates between sprinklers within a subunit is
small. Sprinklers must be properly spaced and the
water distribution patterns from individual sprinklers
must be selected to ensure high uniformity. In
addition, prevailing wind conditions must be
considered to ensure that uniformity remains high for
typical prevailing winds. In general, maximum minus
minimum flow rates from sprinklers in a subunit
should not be greater than 10% of the average
sprinkler flow rate in the subunit. Uniformity should
be higher when chemicals are applied with the
irrigation water since chemical application uniformity
will be limited by the water application uniformity.

For more information on sprinkler irrigation
systems, see IFAS Ext. Cir. 348, Sprinkler Irrigation for
Cold Protection (27), and Cir. 804, Center Pivot
Inigation Systems and Applications in Florida (62).

For microirrigation systems the design water
emission uniformity, EU, is defined as:

EU = 100 [1.0 1.27 C/Sqrt(n)] Q,/Q,

where

EU = subunit design emission uniformity
(%),
C- = emitter manufacturer's coefficient of
variation,
Sqrt(n) = square root of the number of emitters
per plant or 1.0, whichever is greater,
Q, = minimum emitter flow rate within the
subunit (gph), and
Q. = average emitter flow rate within the
subunit (gph).

The minimum acceptable subunit uniformity of
water application (EU) should be 80% for Florida
microirrigation systems. If chemicals (including
fertilizers) are applied with the irrigation water, the
water and chemicals should be applied more
uniformly, thus the minimum acceptable uniformity is
90%. See ASAE (1), FIS (12, 13) and SCS (36)
standards for acceptable uniformities of water
application. See Agricultural Engineering Fact Sheet
AE-70, Principles of Microimigation (18), for more
information on microirrigation system design
considerations.

Subunit uniformity refers to the uniformity of
water application, but it must be expressed in terms


Page 8


of pressure variation (loss) so that the designer can
select pipe sizes. The relationship between flow
variation and pressure variation depends on the
emitter hydraulic characteristics, that is, how the
individual emitter or sprinkler flow varies with
pressure. These data must be obtained from the
emitter manufacturer or by testing a representative
sample of emitters. Manufacturing variation, Cv,
between individual microirrigation emitters must also
be considered in design, and these data should be
provided by the emitter manufacturer.

The type of emitter used in a pressurized
irrigation system affects the system design. Emitter
hydraulic properties affect the allowable pressure
losses in subunits, and manufacturer's variation and
friction losses associated with emitter connections
must be considered when microirrigation systems are
designed.

Lateral pipes are pipes on which the emitters are
mounted. They are typically rigid PVC pipe for
permanent sprinkler systems, aluminum pipe for
portable sprinkler systems, or flexible polyethylene
(PE) pipe for microirrigation systems. Sprinkler
laterals are typically buried for permanent systems
and placed on the surface for portable systems.

Microirrigation laterals are typically installed on
the soil surface or buried at shallow depths. When
laterals are buried, small risers or flexible PE tubes
usually supply water to the emitters on the surface.
In some cases, both laterals and emitters are buried;
however, emitters are normally not buried more than
1 to 3 inches below the surface because upward
capillary water movement in Florida's typical sandy
soils is very limited.

Manifold pipes are pipes which feed the laterals.
Manifolds are normally buried PVC pipe with risers
to connect the laterals. Burial is required to prevent
organic growths in the pipe and to protect it from
deterioration in sunlight. Pipe is connected using
solvent cemented or slip couplings. Short riser pipes
are normally used to conduct water to lateral
pipelines. Risers are normally constructed of either
rigid PVC pipe or flexible PE or PVC tubing.
Flexible tubing is preferred because it minimizes riser
breakage, light cannot penetrate it, and it is protected
against degradation by sunlight.

Manifolds are sometimes placed on the surface.
This arrangement is often used for annual crops such
as vegetables. Surface manifolds are often







Design of Agricultural Irrigation Systems in Florida

constructed from "lay-flat" collapsible hose which is
similar in appearance to fire hose. The manifolds are
then rolled up and stored between crop seasons.

Flush valves should be installed on the ends of
manifolds to permit periodic manual flushing to
minimize clogging problems. To adequately flush a
manifold, a minimum velocity of 1 ft/sec should be
provided. Normally the smallest manifold pipe size
and flush valve required for commercial-scale
installations is 2 inches in order to obtain flow rates
large enough to adequately flush the manifold.

Seepage Systems

For seepage irrigation systems, water is applied to
lateral pipes or ditches, and it moves horizontally at
rates that depend on the soil hydraulic properties.
Depending on soil hydraulic properties, ditch spacings
may range from 20 to 60 feet in sandy soils and up to
300 feet in muck soils. Spacings are computed based
on soil hydraulic properties, slope, water use rates,
system efficiencies, and required water table heights.
Nonuniformity in water table heights will result in
nonuniform production since water moves up into the
crop root zone by soil capillarity.

Seepage irrigation systems require flow rates of 5
to 10 gpm per acre depending on crop water use rates
and irrigation efficiencies. Design of seepage systems
requires calculating lateral spacings needed to
maintain the required water table heights. Closer
spacings produce greater uniformities, while wider
spacings are less expensive. For more information on
seepage irrigation, see IFAS Ext. Cir. 309-C, Seepage
Irrigation for Pastures (28), Cir. 729, Factors to
Consider When Applying Seepage Irigation and
Drainage (31), and Cir. 769, Water Budgeting for High
Water Table Soils (30).

Surface Systems

Surface irrigation requires 1) applying water to
wet the soil surface as quickly as possible and then
maintaining water applications at rates approximately
equal to infiltration rates until the required amount of
water has been applied; or 2) continuously flooding
the soil surface. In Florida, only two types of surface
systems are used, crown flood irrigation of citrus and
Flood irrigation of rice.

In citrus crown flood systems, water is quickly
applied to flood water furrows, then it is allowed to
stand until the required depth has infiltrated, after


Page 9


which the excess is drained. The amounts and times
depend on soil properties, bed widths between
furrows, ET rates, and irrigation efficiencies.
Normally, however, an irrigation requires 2 to 4 days.

In rice flood systems, the production areas are
continuously flooded and the required water
application rates depend on ET rates and irrigation
efficiencies. Irrigation occurs continuously throughout
the growing season until the fields are drained in
preparation for harvest except when adequate rainfall
occurs.

Pumping Systems

An irrigation pumping system must have sufficient
capacity to irrigate all subunits to meet crop water
requirements. Crop water requirements include
evapotranspiration and other requirements such as
cold protection or water required as a carrier for
fertilizer applications, etc. See IFAS Ext. Cir. 822,
Atmospheric Parameters which Affect
Evapotranspiration (8) and Bul. 205, Potential
Evapotranspiration Probabilities and Distributions in
Florida (45).

The pump must have sufficient flow and pressure
for the most extreme subunit conditions. The critical
flow is that of the largest subunit. The critical
pressure subunit is the most distant, the one at the
greatest elevation, or which for other reasons requires
the greatest pressure to deliver its water. Ideally, all
subunits should be of about the same size and have
about the same pressure requirements because an
irrigation pump operates most efficiently at a single
flow rate and pressure.

The total pressure that the pumping system must
produce is the sum of the pressures required to
operate the critical subunit, friction losses through the
mainline (including all losses through valves, filters,
meters, fittings, etc.), and elevation changes including
pumping lift.

For surface water supplies and water at pumping
levels of less than 20 feet in wells, centrifugal pumps
are the most economical option. Low-lift axial-flow
(propeller) pumps may be required in seepage
irrigation systems because of their high flow
capabilities.

For water at depths greater than 20 feet in wells,
turbine pumps must be used. For large systems,
deep-well turbines, with power units on the surface,






Design of Agricultural Irrigation Systems in Florida

are commonly used. For smaller units, submersible
turbines are a less expensive option. With
submersible turbines, electric motors are directly
connected to the pumps and lowered into the well.

For automatic operation, turbine pumps have the
advantage that they do not require priming for the
pump to operate. Conventional centrifugal pumps
require priming to operate. Although self-priming
centrifugal pumps are available, they generally
operate less efficiently than turbines. To avoid
problems with loss of prime, turbines are
recommended for systems that will start and stop
automatically.

For automatic operation, electric motors are
recommended as power units for drip irrigation
systems. They have lower initial costs than internal
combustion engines, especially for smaller sizes.
There may be a demand charge on the electric bill for
their use, especially for larger units. Most power
companies now have off-peak rates for irrigation
pumps. Some power companies have also eliminated
stand-by or demand charges for off-peak users. Local
power company policies will dictate actual costs.

Diesel power units are the most common type of
internal combustion engines used for irrigation in
Florida. They are more efficient than other types of
internal combustion engines. Internal combustion
engines are recommended when irrigation systems
will be used for cold protection because of the
possibility of electric power interruption and loss of
pumping capability on cold nights.

For more information on pumping systems, see
IFAS Ext. Cir. 832, Pumps for Florida Irrigation and
Drainage Systems (20), Cir. 653, Performance of
Irigation Pumping Systems in Florida (55), and Ag.
Eng. Fact Sheets AE-24, Evaluating Irrigation Pumping
Systems (57) and AE-62, Power Requirements and Cost
Estimates for Irrigation Pumping (51). For more
information on wells, see IFAS Ext. Cir. 803, Water
Wells for Florida Irrigation Systems (21).

SELECTION OF OPERATING CONDITIONS

The design of an irrigation system requires that
the designer specify the system operating conditions.
The operating conditions include the operating
pressure and flow rate that must be provided by the
pump.


Page 10


Because the flow rate of a water emitter depends
on pressure, selection of the operating pressure for a
given type of emitter also determines the average flow
rate for the system. Likewise, selecting the average
flow rate determines the operating pressure required
to achieve that flow rate.

Operating Pressure
The operating pressure of an irrigation system is
the pressure at which the typical subunit operates.
For gravity flow systems such as many flood and
seepage systems, water is pumped into open ditches.
In these cases, the only pressure required is the
pressure needed to lift water from its source to its
point of discharge and to overcome friction losses in
the pipelines. If the water source is a well, lift also
includes drawdown in the well. For all water sources,
lift should be calculated based on the lowest expected
water elevation so that pressures would then be
adequate even under drought conditions.

For pressurized irrigation systems, including
sprinkler, microirrigation, and seepage systems which
convey and distribute water from pipelines, the
operating pressure required includes lift, friction
losses, and pressure required to operate the emitters.
Lift is the difference in elevation from the water
source to the emitters in the field, including
drawdown. Friction losses include all losses in
pipelines, valves, fittings, filters, and other
components between the water source and the field
subunits.

The pressure required to operate the emitters
depends on the type of emitter used. For seepage
and microirrigation systems, the emitter pressure is
low, typically less than 30 psi. For sprinkler systems,
the required pressure can range from 20 to 100 psi
depending on the type of sprinkler selected.

High operating pressure increases the cost of
operating an irrigation system because the pumping
cost increases directly with the pressure that the
pump operates against. Low pressure increases pipe
costs because the allowable pressure loss to achieve
a high degree of uniformity of water application is
less, and this requires larger pipe sizes. The final
decision on operating pressure selection must be
based on economics. The optimum set of operating
conditions will only result from a detailed cost
analysis.







Design of Agricultural Irrigation Systems in Florida

Flow Rates
Flow rates required for irrigation depend on many
irrigation system and crop production system factors.
For seepage irrigation, flow rates of 5 to 10 gpm per
acre are required in order to establish and maintain
a field water table. These values can range even
wider depending on site-specific factors such as the
permeability of restrictive layers, depth to water table,
and time of year that the crop is grown.

For sprinkler irrigation, the required flow rate
depends on the sprinkler application rate selected.
Application rates typically range from 0.12 to 0.25
inches per hour (54 to 113 gpm per acre), although
they may be larger if required for freeze protection.
Smaller application rates will be required on heavier
soils and steeper slopes in order to avoid runoff.

For microirrigation systems, flow rates required
will vary depending on the type of emitters selected
and emitter spacings. The flow rate from individual
emitters in a drip irrigation system are rarely greater
than 1 gallon per hour (gph). For spray emitters,
flow rates typically range from 10 to 25 gph per
emitter.

The flow rate required per acre can be as high as
30 to 40 gpm per acre if closely-spaced plants are
drip-irrigated, and it will be much lower for widely
spaced plants. For example, to drip irrigate a
vegetable crop with 7,260 row feet per acre will
require about 35 gpm if 0.5 gpm/100 ft drip tubing is
used, while a crop with 5,000 row feet per acre will
require 25 gpm per acre with the same drip tubing
and only 15 gpm per acre if 0.3 gpm/100 ft drip tubing
is used.

For tree crops such as citrus, microspray emitters
are typically used. Citrus trees will require 25 gpm
per acre for 100 trees per acre and one 15-gph
microspray emitter per tree, and 50 gpm per acre for
200 trees per acre. Sometimes even higher flow rates
are used when microirrigation systems are designed
for freeze protection.

For more information on flow rate requirements
for specific crops, see the irrigation publications or
crop production guides for those crops.


Page 11


SUMMARY

Components of irrigation systems for crop
production in Florida were defined. Design of control
equipment, mainline pipes, system subunits, and
pumping systems were discussed. Considerations in
selecting irrigation system operating conditions,
consisting of operating pressures and flow rates were
presented. An extensive list of IFAS extension
publications was provided for additional information
on the design and installation of various system
components.

REFERENCES

1. ASAE. 1993. ASAE standards 1993: Standards,
engineering practices and data developed and
adopted by the American Society of Ag. Eng.
ASAE, St. Joseph, MI.

2. Boman, BJ. 1989. Distribution patterns of selected
emitters used for microinigation of Florida citrus.
IFAS Ext. Bul. 256. Univ. of Fla.

3. Clark, G.A. and D.Z. Haman. 1988.
Microirigation in mulched bed production systems:
irrigation depths. Ag. Eng. Fact Sheet AE-72.
Univ. of Fla.

4. Clark, G.A., D.Z. Haman and F.S. Zazueta. 1990.
Injection of chemicals into irigation systems: rates,
volumes, and injection periods. IFAS Ext. Bul.
250. Univ. of Fla.

5. Clark, G.A., G.N. Maynard, C.D. Stanley, GJ.
Hochmuth, E.A. Hanlon and D.Z. Haman. 1990.
Inigation scheduling and management of micro-
irrigated tomatoes. IFAS Ext. Cir. 872. Univ. of
Fla.

6. Clark, G.A. and A.G. Smajstrla. 1992. Treating
irrigation systems with chlorine. IAS Ext. Cir.
1039. Univ. of Fla.

7. Clark, G.A., A.G. Smajstrla and D.Z. Haman.
1989. Water hammer in irrigation systems. IAS
Ext. Cir. 828. Univ. of Fla.

8. Clark, G.A., A.G. Smajstrla and F.S. Zazueta.
1989. Atmospheric parameters which affect
evapotranspiration. IAS Ext. Cir. 822. Univ. of
Fla.







Design of Agricultural Irrigation Systems in Florida

Flow Rates
Flow rates required for irrigation depend on many
irrigation system and crop production system factors.
For seepage irrigation, flow rates of 5 to 10 gpm per
acre are required in order to establish and maintain
a field water table. These values can range even
wider depending on site-specific factors such as the
permeability of restrictive layers, depth to water table,
and time of year that the crop is grown.

For sprinkler irrigation, the required flow rate
depends on the sprinkler application rate selected.
Application rates typically range from 0.12 to 0.25
inches per hour (54 to 113 gpm per acre), although
they may be larger if required for freeze protection.
Smaller application rates will be required on heavier
soils and steeper slopes in order to avoid runoff.

For microirrigation systems, flow rates required
will vary depending on the type of emitters selected
and emitter spacings. The flow rate from individual
emitters in a drip irrigation system are rarely greater
than 1 gallon per hour (gph). For spray emitters,
flow rates typically range from 10 to 25 gph per
emitter.

The flow rate required per acre can be as high as
30 to 40 gpm per acre if closely-spaced plants are
drip-irrigated, and it will be much lower for widely
spaced plants. For example, to drip irrigate a
vegetable crop with 7,260 row feet per acre will
require about 35 gpm if 0.5 gpm/100 ft drip tubing is
used, while a crop with 5,000 row feet per acre will
require 25 gpm per acre with the same drip tubing
and only 15 gpm per acre if 0.3 gpm/100 ft drip tubing
is used.

For tree crops such as citrus, microspray emitters
are typically used. Citrus trees will require 25 gpm
per acre for 100 trees per acre and one 15-gph
microspray emitter per tree, and 50 gpm per acre for
200 trees per acre. Sometimes even higher flow rates
are used when microirrigation systems are designed
for freeze protection.

For more information on flow rate requirements
for specific crops, see the irrigation publications or
crop production guides for those crops.


Page 11


SUMMARY

Components of irrigation systems for crop
production in Florida were defined. Design of control
equipment, mainline pipes, system subunits, and
pumping systems were discussed. Considerations in
selecting irrigation system operating conditions,
consisting of operating pressures and flow rates were
presented. An extensive list of IFAS extension
publications was provided for additional information
on the design and installation of various system
components.

REFERENCES

1. ASAE. 1993. ASAE standards 1993: Standards,
engineering practices and data developed and
adopted by the American Society of Ag. Eng.
ASAE, St. Joseph, MI.

2. Boman, BJ. 1989. Distribution patterns of selected
emitters used for microinigation of Florida citrus.
IFAS Ext. Bul. 256. Univ. of Fla.

3. Clark, G.A. and D.Z. Haman. 1988.
Microirigation in mulched bed production systems:
irrigation depths. Ag. Eng. Fact Sheet AE-72.
Univ. of Fla.

4. Clark, G.A., D.Z. Haman and F.S. Zazueta. 1990.
Injection of chemicals into irigation systems: rates,
volumes, and injection periods. IFAS Ext. Bul.
250. Univ. of Fla.

5. Clark, G.A., G.N. Maynard, C.D. Stanley, GJ.
Hochmuth, E.A. Hanlon and D.Z. Haman. 1990.
Inigation scheduling and management of micro-
irrigated tomatoes. IFAS Ext. Cir. 872. Univ. of
Fla.

6. Clark, G.A. and A.G. Smajstrla. 1992. Treating
irrigation systems with chlorine. IAS Ext. Cir.
1039. Univ. of Fla.

7. Clark, G.A., A.G. Smajstrla and D.Z. Haman.
1989. Water hammer in irrigation systems. IAS
Ext. Cir. 828. Univ. of Fla.

8. Clark, G.A., A.G. Smajstrla and F.S. Zazueta.
1989. Atmospheric parameters which affect
evapotranspiration. IAS Ext. Cir. 822. Univ. of
Fla.






Design of Agricultural Irrigation Systems in Florida

9. Clark, G.A., A.G. Smajstrla, F.S. Zazueta, F.T.
Izuno, BJ. Boman, DJ. Pitts and D.Z. Haman.
1991. Uses of water in Florida crop production
systems. IFAS Ext. Cir. 940. Univ. of Fla.

10. Clark, G.A. C.D. Stanley and P.R. Gilreath. 1990.
A preliminary guide to fully enclosed subsurface
irrigation. IFAS Ext. Special Series Rpt. SS-AGE-
006. Univ. of Fla.

11. Clark, G.A. C.D. Stanley and A.G. Smajstrla.
1988. Microinigation on mulched bed systems:
components, system capacities and management.
IFAS Ext. Bul. 245. Univ. of Fla.

12. FIS. 1989. Standards and specifications for turf
and landscape irrigation systems. Florida
Irrigation Society, Winter Park.

13. FIS. 1991. Standards and specifications for
agricultural solid-set sprinkler and microirrigation
systems. Florida Irrigation Society, Winter Park.

14. Haman, D.Z. and G.A. Clark. 1988. Fittings and
connections for flexible polyethylene pipe used in
microirigation systems. Ag. Eng. Fact Sheet AE-
69. Univ. of Fla.

15. Haman, D.Z., GA. Clark and DJ. Pitts. 1991.
Excavated pond construction in Florida. IFAS Ext.
Cir. 939. Univ. of Fla.

16. Haman, D.Z., G.A. Clark and A.G. Smajstrla.
1989. Positive displacement pumps for agricultural
applications. IFAS Ext. Cir. 826. Univ. of Fla.

17. Haman, D.Z., G.A. Clark and A.G. Smajstrla.
1992. Irigation of lawns and gardens. IFAS Ext.
Cir. 825. Univ. of Fla.

18. Haman, D.Z. and F.T. Izuno. 1988. Principles of
microirrigation. Ag. Eng. Fact Sheet AE-70.
Univ. of Fla.

19. Haman, D.Z., F.T. Izuno and G.A. Clark. 1989.
Valves in irrigation systems. IFAS Ext. Cir. 824.
Univ. of Fla.

20. Haman, D.Z., F.T. Izuno and A.G. Smajstrla.
1989. Pumps for Florida irrigation and drainage
systems. IFAS Ext. Cir. 832. Univ. of Fla.


Page 12


21. Haman, D.Z., A.G. Smajstrla and G.A. Clark.
1988. Water wells for Florida irrigation systems.
IFAS Ext. Cir. 803. Univ. of Fla.

22. Haman, D.Z., A.G. Smajstrla and F.S. Zazueta.
1987. Media filters for trickle irrigation in Florida.
Ag. Eng. Fact Sheet AE-57. Univ. of Fla.

23. Haman, D.Z., A.G. Smajstrla and F.S. Zazueta.
1987. Settling basins for trickle irrigation in Florida.
Ag. Eng. Fact Sheet AE-65. Univ. of Fla.

24. Haman, D.Z., A.G. Smajstrla and F.S. Zazueta.
1987. Water quality problems affecting
microirrigation in Florida. IFAS Ext. Special
Series Rpt. SS-AGE-805. Univ. of Fla.

25. Haman, D.Z., A.G. Smajstrla and F.S. Zazueta.
1988. Screen filters in trickle irrigation systems. Ag.
Eng. Fact Sheet AE-61. Univ. of Fla.

26. Haman, D.Z., A.G. Smajstrla and F.S. Zazueta.
1990. Chemical injection methods for irrigation.
IFAS Ext. Cir. 864. Univ. of Fla.

27. Harrison, D.S., J.F. Gerber and R.E. Choate.
1987. Sprinkler irrigation for cold protection. IFAS
Ext. Cir. 348. Univ. of Fla.

28. Harrison, D.S., J.M. Myers and D.W. Jones.
1974. Seepage irrigation for pastures. IFAS Ext.
Cir. 309-C. Univ. of Fla.

29. Harrison, D.S. and A.G. Smajstrla. 1985. Plans
for trickle and sprinkler irrigation for the home and
garden. Ag. Eng. Fact Sheet AE-29. Univ. of Fla.

30. Izuno, F.T. 1987. Water budgeting for high water
table soils. IFAS Ext. Cir. 769. Univ. of Fla.

31. Izuno, F.T. and D.Z. Haman. 1987. Factors to
consider when applying seepage irrigation and
drainage. IFAS Ext. Cir. 729. Univ. of Fla.

32. Izuno, F.T. and D.Z. Haman. 1987. Basic
irrigation terminology. Ag. Eng. Fact Sheet AE-66.
Univ. of Fla.

33. Pitts, DJ., D.Z. Haman and A.G. Smajstrla. 1990.
Causes and prevention of emitter plugging in
microirrigation systems. IFAS Ext. Bul. 258. Univ.
of Fla.







Design of Agricultural Irrigation Systems in Florida

34. Pitts, DJ. and A.G. Smajstrla. 1989. Inigation
systems for crop production in Florida: descriptions
and costs. WAS Ext. Cir. 821. Univ. of Fla.

35. Pitts, DJ., A.G. Smajstrla, D.Z. Haman and G.A.
Clark. 1990. Irrigation costs for tomato production
in Florida. Ag. Eng. Fact Sheet AE-74. Univ. of
Fla.


36. SCS. 1982. Florida Irrigation Guide.
Conservation Service. Gainesville.


Soil


Page 13


evapotranspiration probabilities and distributions in
Florida. IFAS Ext. Bul. 205. Univ. of Fla.

46. Smajstrla, A.G., D.Z. Haman and F.S. Zazueta.
1992. Calibration of fertilizer injectors for
agricultural irrigation systems. IFAS Ext. Cir. 1033.
Univ. of Fla.

47. Smajstrla, A.G. and D.S. Harrison. 1981. Weirs
for open-channel flow measurement. Ag. Eng. Fact
Sheet AE-25. Univ. of Fla.


37. Smajstrla, A.G. 1992. Shunt flow meters for
irrigation water measurement. Ag. Eng. Fact Sheet
AE-155. Univ. of Fla.

38. Smajstrla, A.G. 1993. Measuring irrigation water.
Ag. Eng. Fact Sheet AE-156. Univ. of Fla.

39. Smajstrla, A.G., W.G. Boggess, BJ. Boman, G.A.
Clark, D.Z. Haman, G.W. Knox, SJ. Locascio,
TA. Obreza, L.R. Parsons, F.M. Rhoads, T.
Yeager and F.S. Zazueta. 1993. Microinigation in
Florida: systems, acreage and costs. IFAS Ext. Bul.
276. Univ. of Fla.

40. Smajstrla, A.G., BJ. Boman, G.A. Clark, D.Z.
Haman, D.S. Harrison, F.T. Izuno, DJ. Pitts and
F.S. Zazueta. 1991. Efficiencies of Florida
agricultural irrigation systems. IFAS Ext. Bul. 247.
Univ. of Fla.

41. Smajstrla, A.G., BJ. Boman, G.A. Clark, D.Z.
Haman, DJ. Pitts and F.S. Zazueta. 1990. Field
evaluation of microinigation water application
uniformity. IFAS Ext. Bul. 265. Univ. of Fla.

42. Smajstrla, A.G., BJ. Boman, G.A. Clark, D.Z.
Haman, DJ. Pitts and F.S. Zazueta. 1990. Field
evaluation of irrigation systems: solid set or portable
sprinkler systems. IFAS Ext. Bul. 266. Univ. of
Fla.

43. Smajstrla, A.G., BJ. Boman, G.A. Clark, D.Z.
Haman, F.T. Izuno and F.S. Zazueta. 1988.
Basic irrigation scheduling in Florida. IFAS Ext.
Bul. 249. Univ. of Fla.

44. Smajstrla, A.G. and G.A. Clark. 1992. Florida
irrigation systems. IFAS Ext. Cir. 1035. Univ. of
Fla.

45. Smajstrla, A.G., G.A. Clark, S.F. Shih, F.S.
Zazueta and D.S. Harrison. 1984. Potential


48. Smajstrla, A.G. and D.S. Harrison.
meters for water flow measurement.
Sheet AE-22. Univ. of Fla.


1982. Orifice
Ag. Eng. Fact


49. Smajstrla, A.G. and D.S. Harrison. 1985.
Measurement of soil water for irigation
management. IFAS Ext. Cir. 532. Univ. of Fla.

50. Smajstrla, A.G. and D.S. Harrison. 1985.
Selection and use of impeller meters for irrigation
water measurement. Ag. Eng. Fact Sheet AE-18.
Univ. of Fla.

51. Smajstrla, A.G. and D.S. Harrison. 1988. Power
requirements and cost estimates for irrigation
pumping. Ag. Eng. Fact Sheet AE-62. Univ. of
Fla.

52. Smajstrla, A.G., D.S. Harrison, WJ. Becker, F.S.
Zazueta and D.Z. Haman. 1991. Florida
backflow prevention requirements for agricultural
irrigation systems. IFAS Ext. Bul. 217. Univ. of
Fla.

53. Smajstrla, A.G., D.S. Harrison and G.A. Clark.
1987. Irigation lateral costs per acre. Ag. Eng.
Fact Sheet AE-30. Univ. of Fla.

54. Smajstrla, A.G., D.S. Harrison and F.X. Duran.
1985. Tensiometers for soil moisture measurement
and irrigation scheduling. IFAS Ext. Cir. 487.
Univ. of Fla.

55. Smajstrla, A.G., D.S. Harrison and J.C. Good.
1985. Performance of irrigation pumping systems in
Florida. IFAS Ext. Cir. 653. Univ. of Fla.

56. Smajstrla, A.G., D.S. Harrison, D.Z. Haman and
F.S. Zazueta. 1992. Irrigated acreage in Florida.
IFAS Ext. Cir. 1030. Univ. of Fla.







Design of Agricultural Irrigation Systems in Florida

57. Smajstrla, A.G., D.S. Harrison and J.M. Stanley.
1985. Evaluating irigation pumping systems. Ag.
Eng. Fact Sheet AE-24. Univ. of Fla.

58. Smajstrla, A.G., D.S. Harrison and F.S. Zazueta.
1985. Agricultural water measurement. IFAS Ext.
Bul. 207. Univ. of Fla.

59. Smajstrla, A.G., D.S. Harrison, F.S. Zazueta, L.R.
Parsons and K.C. Stone. 1987. Trickle irrigation
scheduling for Florida citrus. IFAS Ext. Bul. 208.
Univ. of Fla.

60. Smajstrla, A.G., F.S. Zazueta, G.A. Clark and DJ.
Pitts. 1989. Irrigation scheduling with evaporation
pans. IFAS Ext. Bul. 254. Univ. of Fla.

61. Smajstrla, A.G., F.S. Zazueta and D.Z. Haman.
1986. Selection of pressure tanks for water supply
systems. IFAS Ext. Cir. 741. Univ. of Fla.

62. Smajstrla, A.G., F.S. Zazueta and D.Z. Haman.
1988. Center pivot irrigation systems and
applications in Florida. IFAS Ext. Cir. 804. Univ.
of Fla.

63. Smajstrla, A.G., F.S. Zazueta and D.Z. Haman.
1989. Potential impacts of improper irrigation
system design. Ag. Eng. Fact Sheet AE-73. Univ.
of Fla.

64. Watson, D.G. 1992. IFAS microcomputer
software catalog. Univ. of Fla.

65. Zazueta, F.S. 1985. Understanding the concepts of
uniformity and efficiency in irrigation. Ag. Eng.
Fact Sheet AE-43. Univ. of Fla.

66. Zazueta, F.S., D. Gilpin-Hudson, A.G. Smajstrla
and D.Z. Haman. 1985. Control +: a computer
controllerfor irrigation systems. IFAS Ext. Cir. 688
(software). Univ. of Fla.

67. Zazueta, F.S. and A.G. Smajstrla. 1986. IR-
CONTROL: a computer controller for irrigation
systems. IFAS Ext. Cir. 705 (software). Univ. of
Fla.

68. Zazueta, F.S. and A.G. Smajstrla. 1992.
Microcomputer-based control of irrigation systems.
Applied Engineering in Agriculture 8:593-596.


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69. Zazueta, F.S., A.G. Smajstrla and D.Z. Haman.
1989. Water management utilities. IFAS
Microcomputer Software #009. Univ. of Fla.

70. Zazueta, F.S., A.G. Smajstrla and D.S. Harrison.
1986. Computer control of mister systems for
nursery propagation houses. IFAS Ext. Cir. 670
(software). Univ. of Fla.

71. Zazueta, F.S., A.G. Smajstrla and D.S. Harrison.
1986. Glossary of trickle irrigation terms. Ag. Eng.
Fact Sheet AE-45. Univ. of Fla.