Group Title: Circular
Title: Irrigation systems for crop production in Florida
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 Material Information
Title: Irrigation systems for crop production in Florida descriptions and costs
Series Title: Circular
Physical Description: 8 p. : ; 28 cm.
Language: English
Creator: Pitts, Donald J ( Donald James )
Smajstrla, A. G ( Allen George )
Publisher: Florida Cooperative Extension Service
Place of Publication: Gainesville
Publication Date: 1989
 Subjects
Subject: Irrigation -- Florida   ( lcsh )
Irrigation engineering -- Florida   ( lcsh )
Irrigation -- Equipment and supplies -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Bibliography: Includes bibliographical references (p. 5).
Statement of Responsibility: D.J. Pitts and A.G. Smajstrla.
General Note: Title from caption.
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Bibliographic ID: UF00014484
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 - AAA6924
ltuf - AJQ7627
oclc - 28923232
alephbibnum - 001833514

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Irrigation Systems for Crop Production in Florida: Descriptions and Costs1

D.J. Pitts and A.G. Smajstrla2


Although Florida receives between 45 and 65
inches of rainfall annually, irrigation is required for
commercial production of many of the agricultural
crops grown in the state. This requirement is due to
a number of factors:

* typical sandy soils have limited water-holding
capacity,

*seasonal distribution of rainfall is uneven with
extended dry periods common, and

* the high economic value and high costs of other
production factors for many Florida crops make
the relative cost of irrigation small by comparison.

In fact, more water is withdrawn for irrigation in
Florida than in all other states east of the Mississippi
river combined (Edward and Patton, 1984). Currently,
Florida ranks tenth among all states in the United
States in the number of irrigated acres (Irrigation
Journal, 1987). In addition to providing water to
meet the evapotranspiration demands of crops, some
irrigation methods can provide freeze protection and
reduced heat stress, as well as an economical means
of applying fertilizers and pesticides (Burman et al.,
1980).

Irrigation systems currently in use in Florida can
be broadly classified as subsurface, flood, sprinkler
and micro. There are several methods of subsurface
irrigation. However, with each an artificial water
table is maintained, and water reaches the root zone
by capillary forces. Flood irrigation has limited
application, and is practiced primarily with rice on
organic soils. Overhead sprinkler irrigation is the


application of water through a spray device. Usually
the water is applied over the top of the crop canopy,
though sometimes under-tree sprinklers are used.
Microirrigafion includes drip, trickle and
microsprinkler devices.

Each irrigation method has advantages and
disadvantages that need to be considered when
selecting a system for a specific application. The
decision as to which irrigation system is most
appropriate is dependent on many factors, among
which are: topography, soil, requirements for freeze
protection or plant establishment, availability and
quality of water, disease factors, cost-of pumping and
labor, initial system cost and other economic factors.

The efficiency of an irrigation system is also an
important element in the decision on which irrigation
method to employ. Irrigation efficiency has several
components. The water conveyance efficiency (Ec)
represents the losses in transporting the irrigation
water from the source to the field where it is to be
applied. Conveyance efficiency is the ratio of the
volume of water delivered to the volume of water
placed in the conveyance system. Application
efficiency (E,) is the ratio of the volume of water
stored in the root zone to the volume of water
delivered by the irrigation system. Reservoir storage
efficiency (E5) is the ratio of the volume of water
available from the reservoir to the volume of water
delivered to the reservoir. The overall irrigation
efficiency of'a system (Eo) is the product of the
efficiencies of the components. More information on
irrigation system efficiencies is available in IFAS
Extension Bulletin 247 "Efficiencies of Florida
Agricultural Irrigation Systems."


1. This document was published May 1989 as Circular 821, Florida Cooperative Extension Service. For more information, contact your county
Cooperative Extension Service office.
2. Former Assistant Professor, Southwest Florida Research and Education Center, Immokalee ,and Professor, Agricultural Engineering
Department, respectively, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville.

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, or national origin.
Florida Cooperative Extension Service / Institute of Food and Agricultural Sciences / University of Florida / John T. Woeste, Dean
""trSITY OF FLORIDA LIBRARIES







Irrigation Systems for Crop Production in Florida: Descriptions and Costs


This publication describes the various types of
irrigation systems used in Florida, their applications,
limitations, and estimated costs. Characteristics of
systems are presented in Table 1. Table 2
summarizes estimated labor requirements and costs.

SUBSURFACE IRRIGATION

Florida has about one million acres utilizing
subsurface irrigation (Irrigation Journal, 1987).
Subsurface irrigation has historically been one of the
most common forms of irrigation practiced in Florida.
Under subsurface irrigation, water is applied to the
field through lateral ditches or underground pipes
spaced on centers from 10 to 200 feet apart from
which water moves horizontally by subsurface flow to
form a perched (mounded) water table on an existing
hardpan or on a naturally occurring high water table.
Water then moves upward to the root zone by
capillary forces. This irrigation method is used with
a variety of crops including citrus, sugarcane,
vegetables, pasture, and hay. There are four main
variations of sub-surface irrigation practiced in
Florida: open ditch seepage, semi-closed seepage,
sub-irrigation and crown flood.

Seepage Systems

Open ditch seepage irrigation is common on
vegetable crops and sugarcane. With this method
water is conveyed from the pump to the field by open
field ditches and then is distributed through the field
by a network of lateral ditches. The water table is
generally held at a constant level. Due to deep
percolation and evaporation, there may be significant
conveyance losses with this method.

Conveyance losses are eliminated with the
semi-closed seepage system since water is brought to
the field through underground PVC pipe. Lateral
ditches are generally shallower and closer together.
They are often installed on a grade, and the irrigation
water is either continuously or periodically distributed
through the ditches. Therefore, with these systems,
the perched water table may be held constant or
allowed to fluctuate. For both the open ditch and the
semi-closed seepage methods, the ditches serve both
for drainage and for irrigation.
1 0 I



FIc -


Sub-irrigation

Water is both conveyed to and distributed through
the field by underground pipe with sub-irrigation.
The field distribution pipe is perforated and can
function both for drainage and irrigation. Clogging
problems may develop in the perforated pipe due to
iron ocher deposits (Ford, 1987).

Crown Flood

Crown flood subsurface irrigation is common with
citrus. With this method, raised beds are formed on
which the trees are planted. The beds provide
elevation above what is often a naturally occurring
high water table, allowing for more root development.
The resulting furrows between the beds are used to
distribute water for irrigation and to provide a flow
path for drainage water.

Subsurface irrigation requires flat topography, a
soil layer with limiting permeability, and soils with a
high degree of lateral hydraulic conductivity, such as
the sandy flatwoods soils and the organic soils of
south Florida. The efficiencies of these methods are
quite variable and are dependent on the depth to the
naturally occurring water table, the permeability of
the hardpan, and management of the system.
Efficiencies are generally low, ranging from 20 to 60
percent. Major advantages of these systems are low
initial costs and low levels of management that is
required. The well or water source capacity normally
required ranges from 8 to 25 gpm/ac, but is
sometimes more, depending on irrigation system
efficiency.

SPRINKLER SYSTEMS

Sprinkler irrigation systems are adaptable to many
crops, soils -and topographical conditions. These
systems are common in Florida and can be
categorized by how they are moved or cycled to
irrigate a field. Sprinkler systems can be grouped into
the following broad categories: solid set, portable set,
guns, center pivots, and lateral moves.

Solid Set Systems

Solid set systems take two forms:


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Irrigation Systems for Crop Production in Florida: Descriptions and Costs


*an underground network of PVC piping
permanently installed with sprinklers that provide
coverage for the entire area to be irrigated, or

* above-ground portable piping systems which are
placed in the field at the start of the irrigation
season and are left in place during the entire
season.

Both of these systems have high initial costs because
pipe and sprinklers must be bought to cover the
entire area at once.

Due to these high initial cost, these systems are
generally limited to use on high value crops such as
ornamentals, citrus, orchards, vegetables and for lawns
and golf courses. The portable solid set system
usually consists of aluminum pipes laid out to irrigate
the entire field in one set to minimize labor.

Solid set systems can be automated to operate in
zones and therefore require little labor. In addition,
they have the capacity to deliver fertilizer and
chemicals directly to the crop through the irrigation
system (fertigation). These systems can also be used
to reduce heat stress by intermittent sprinkling. Solid
set systems are common in Florida, covering more
than 200,000 acres, not including home and golf
course sprinkler systems (Irrigation Journal, 1987).
These systems, if properly designed and operated, can
have application efficiencies from 70 to 86 percent.
A disadvantage of this method on some crops is that
leaf wetting can promote disease and pest problems.

If freeze or frost protection is required, these
systems can serve a dual purpose, thus justifying the
large investment cost. As many as 80,000 acres of
ornamental crops in Florida have frost and freeze
protection, as well as irrigation needs, provided by
this method (Irrigation Journal, 1987). When
operating for freeze protection, pumping capacity
requirements may be as high as 115 gpm/acre.
Researchers have reported success in providing
protection for strawberries, citrus, vegetables and
ornamentals against temperatures as low as 15
degrees F (Burman et al., 1980).

Portable Set Systems

Portable set systems are above-ground, moveable
systems in which only a portion of the field is covered
at one time. These systems usually consist of


aluminum pipe that is coupled together and can be
easily disassembled to be moved to different parts of
the field. The advantage of portable over solid set
systems is the lower initial cost. The disadvantage is
the high labor requirement for moving the piping
system, which is normally moved by hand. This labor
requirement is of particular concern where
coarse-textured soils with low water-holding capacities
are common, thus requiring frequent moves of the
irrigation system. These systems can provide only
limited freeze protection, and only to that specific
portion of the field that is being irrigated at the time.

Guns

Guns are simply large sprinklers that can be
moved by hand or tractor or that are self-propelled.
The self-propelled (traveling) guns were first
introduced in the 1960s and are still in common use.
Their capacities range from 100 to 1000 gpm with
operating pressures from 60 to 120 psi. These high
operating pressures have large power requirements,
causing high energy costs.

An advantage of traveling guns is that they can be
used to irrigate irregularly shaped fields. They have
medium initial investment costs and labor
requirements (see Tables 1 and 2). Because of high
application rates, land irrigated by this method should
be relatively flat and have soil with a high infiltration
capacity. Irrigation efficiency varies (60 to 75
percent) depending on operating conditions. The well
or water source capacity usually required is from 8 to
12 gpm/acre. These systems are in extensive use
throughout Florida with approximately 150,000 acres
currently being irrigated by this method (Irrigation
Journal, 1987).

Center Pivots and Lateral Moves

The center pivot and lateral move sprinklers are
large, self-propelled and highly mechanized irrigation
systems. They provided major advancements in
irrigation technology in the 1960s. These systems
have gained widespread usage throughout the United
States for agronomic crop production because they
are relatively efficient, low in labor and operating
costs, and medium in initial investment cost. The two
common types of drive units are hydraulic (water) and
electric.


Page 3







Irrigation Systems for Crop Production in Florida: Descriptions and Costs


The center pivot is a radial-move pipeline that
rotates around a pivot point. These systems can be
towable and thus moved from one field to another to
reduce the cost per acre. They cover a circular area,
but can be attached with an optional end gun or
cornering mechanism to irrigate the corners of the
field. The lateral move is a self-propelled sprinkler
system that travels in a linear direction. These
systems have guidance and water feed mechanisms
that allow the irrigation of rectangular fields.
Although similar to the center-pivot, the lateral move
has higher labor and initial investment costs.

These systems are suitable for many crops and are
adaptable to most soils and topography with slopes
less than 15 percent. They can be used for fertigation
and the application of other chemicals. The length of
these systems ranges from 300 to 2600 ft with 1/4 mile
being most common. Operating pressures range from
15 to 70 psi. The lower pressure systems are
becoming more common due to reduced pumping
costs. With proper design and operation, these
systems can be very efficient; 70 to 80 percent
efficiency is common. They require a water source
capacity ranging from 5 to 8 gpm per acre. Center
pivot and lateral move irrigation systems currently
irrigate more than 130 thousand acres in Florida
(Irrigation Journal, 1987). For more discussion on
center pivot irrigation systems, see IFAS Extension
Circular 804.

MICROIRRIGATION

Microirrigation systems are the most recent
advancement in irrigation technology. These systems
distribute water through a network of plastic pipe
directly to the soil near the plant by small frequent
applications through devices called emitters. A micro-
irrigation system consists of a water source, pump,
power unit, filtration and chemical injection
equipment, main pipelines, manifold pipelines, lateral
pipelines and emitters. The term microirrigation is a
general term which includes several specific types of
systems, including drip or trickle, microsprinklers,
bubbler line sources, perforated pipes and seepage
hoses.

Microirrigation can dramatically reduce the
amount of water applied compared to some of the
other irrigation methods. It also has other potential
advantages such as:


* providing adequate moisture to the root zone at
all times,

* minimizing weed growth since the entire soil
surface is not irrigated, and

* controlling nutrient application, thus minimizing
leaching.

Some of the disadvantages of the microirrigation
systems are:

* medium to high initial cost,

* high level of management particularly on the
sandy soils common in Florida, and

* emitter clogging can be a serious problem if
proper precautions are not taken with regard to
water treatment.

For more information on causes and prevention of
emitter plugging, see IFAS Bulletin 258.

These irrigation systems operate at low pressures
(less than 30 psi), thus reducing pumping costs in
comparison to some other systems. The water
capacity requirements generally range from 5 to 10
gpm/acre. Efficiencies are typically high, ranging from
75 to 90 percent if properly designed and operated.
Currently in Florida over 350,000 acres are being
irrigated by some form of microirrigation (Irrigation
Journal, 1987).

There are two primary categories of
microirrigation systems in use in Florida: drip and
microsprinklers. Drip type microirrigation systems
apply water from discrete point source emitters
attached to or molded into lateral lines.
Microsprinklers spray water through the air from a
network of plastic lateral pipes.

Drip

In Florida, drip irrigation systems are common
with vegetable, citrus and ornamental crops. There
are two basic types of drip irrigation systems in use:
permanent lateral lines (5 to 10 years of useful life),
and disposal tubing that is replaced after each crop.
The permanent lateral is common with citrus
production while the disposable is used more often
with vegetable production. Emitter discharge rates


Page 4







Irrigation Systems for Crop Production in Florida: Descriptions and Costs


range from 0.3 gph to 2.0 gph with 1 gph being most
common. Operating pressures typically range from 10
to 20 psi.

Microsprinklers

Since Florida's typically sandy soils limit the
lateral movement of water from the emitter, reduced
wetted volume of the soil results. To overcome this
limitation with drip systems, microsprinklers are often
used. With microsprinklers the flow rate and wetted
volume of soil is significantly greater than the
traditional drip irrigation systems. Flow rates range
from 10 to 30 gph per sprayer with wetted diameters
from 5 to 30 feet. This system is most common in
citrus production. Distributing water over a larger
area has resulted in increased yields. In addition,
larger flow rates have reduced filtration requirements
and plugging problems.

ENERGY COSTS IN IRRIGATION

Pumping costs are a major factor to consider
when choosing an irrigation system and its power
source. The power and energy requirements of a
pumping unit depend upon the pumping rate,
irrigation system pressure requirements, friction losses
within the distribution system and pump efficiency.
The cost and convenience of the fuel sources needs to
be evaluated in the decision on which type of power
unit to purchase. For more information on irrigation
pumping costs see IFAS Extension Publication AE-62.

SUMMARY

Irrigation is required for much of the crop
production in Florida. The type of irrigation system
that should be used is specific to the crop and
location. Such factors as the availability and the cost
of irrigation water, and the requirements for freeze
protection, fertigation or heat stress reduction are all
important in determining which irrigation system is
most appropriate for a particular application. In the
final analysis, economic factors such as cost of labor
or fuel, initial system cost, and interest rates are of
primary importance for determining which system to
purchase.


This circular provides a brief description of the
various irrigation systems used in Florida, their
applications, limitations, and some relative cost
information. Publications providing more detailed
information on the various irrigation systems were
referenced. They are available by contacting your
county Extension agent.

REFERENCES

Burman, R.D., P.R. Nixon, J.L. Wright and W.O.
Pruit. 1980. Water Requirements in: Design and
Operation of Farm Inigation Systems. M.E.
Jensen, ed. pp. 215-216. ASAE. St. Joseph, MI.


Edward, F.A. and D.J. Patton. 1984.
Resources Atlas of Florida. Florida
University Press. Tallahassee, FL.


Water
State


Ford, H.W. 1987. Iron Ocher and Related Sludge
Deposits in Subsurface Drain Lines. Extension
Circular 671 IFAS, University of Florida,
Gainesville, FL.


Irrigation Journal. 1987.
January/February, pp. 23-31.


Inigation Survey.


Page 5







Irrigation Systems for Crop Production in Florida: Descriptions and Costs


Table 1. Characteristics of Florida irrigation systems.

System Area Initial Operating Efficiency Estimated Life
Type (acres) Costz'y Pressure (percent) (years)
($/ac) (psi)

Subsurface
Seepage Variable 30-100 5-20 20-60 20
Flood Variable 30-100 5-10 20-50 20
Sprinkler
Solid-set Variable 1200-2000 15-60 70-85 20
Gun 10-100 300-400 60-120 60-75 10
Pivot 40-500 300-500 15-70 65-80 15
Microirrigation
Micro Various 600-1200 10-30 75-90 10
ZInitial cost estimates include water supply unit.
YDoes not include the cost of land forming.



Table 2. Estimates of labor, pumping and annual costs of Florida irrigation systems.

System Annual Labor Pumping Total Annual
Type Pumpage (man-hr/ Costsz Costsx
(inches) ac-inch) ($/ac-inch) ($/ac-inch)

Subsurface
Seepage 30-90 0.05-0.1 0.75-1.50 75-150
Flood 30-90 0.05-0.1 0.75-1.50 75-150
Sprinkler
Solid set 10-25 0.04-0.6 1.75-2.50 350-500
Traveling Gun 10-30 0.1-0.5 3.00-5.00 300-500
Center Pivot 10-25 0.05-0.1 1.00-1.75 75-200
Microirrigation
Micro 10-25 0.1-0.5y 1.00-1.75 200-350
zWill vary depending on year, crop and location.
YDepends heavily on system maintenance requirements, water quality, filtration needs, etc.
XAssumed 10 percent interest rate.


Page 6






Irrigation Systems for Crop Production in Florida: Descriptions and Costs


Table 3a. Pumping Costs per HP-hour with electricity as fuel source (based on motor efficiency of 88% 1.18
hp hr/KWH).
Electricity Cost per Kilowatt-Hour
Pump Load (HP) $ .05 $ .06 $ .07 $ .08 $ .10 $ .12

:.. i!::(10 $.42 $.51 $.59 $.68 $.85 $1.02
20 .84 1.02 1.19 1.36 1.69 2.03
30 1.27 1.53 1.78 2.03 2.54 3.05
40 1.69 2.03 2.37 2.71 3.39 4.07
50 2.12 2.54 2.97 3.39 4.24 5.08
75 3.18 3.81 4.45 5.08 6.36 7.63
100 4.24 5.08 5.93 6.78 8.47 10.17 .
125 5.30 6.35 7.41 8.48 10.59 12.71
150 6.36 7.62 8.90 10.17 12.71 15.26


Table 3b. Pumping costs per HP-hr with gasoline as fuel source (based on 11.54 hp-hr/gal corrected for 5%
drive loss).

Fuel Cost Per Gallon
Pump Load (HP) $ .80 $ .90 $ 1.00 $1.20 $ 1.40 $ 1.60

10 $ .69 $ .78 $ .87 $ 1.04 $ 1.21 $ 1.39
20 1.39 1.56 1.73 2.08 2.43 2.77
30 2.08 2.34 2.60 3.12 3.64 4.16
40 2.77 3.12 3.47 4.16 4.85 5.55
50 3.47 3.90 4.33 5.20 6.07 6.93
75 5.20 5.85 6.50 7.80 9.10 10.40
100 6.93 7.80 8.67 10.40 12.13 13.86
125 8.66 9.75 10.84 13.00 15.16 17.33
150 10.40 11.70 13.00 15.60 18.20 20.79


Page 7







Irrigation Systems for Crop Production in Florida: Descriptions and Costs


Table 3c. Pumping costs per HP-hr with propane as fuel source (based on 9.2 hp-hr/gal corrected for 5% drive
loss).
Fuel Cost Per Gallon

Pump Load (HP) $ .70 $.80 $ .90 $1.00 $1.20 $1.40

10 $ .76 $.87 $.98 $1.09 $1.30 $1.52
20 1.52 1.74 1.96 2.17 2.61 3.04
30 2.28 2.61 293 3.26 3.91 4.57

40 3.04 3.48 3.91 4.35 5.22 6.09
50 3.80 4.35 4.89 5.43 6.52 7.61
75 5.71 6.52 7.34 8.15 9.78 11.41
100 7.61 8.70 9.78 10.87 13.04 15.22
150 11.42 13.05 14.67 16.31 19.56 22.83



Table 3d. Pumping costs per HP-hr with diesel as fuel source (based on 14.58 hp-hr/gal corrected for 5% drive
loss).
Fuel Cost Per Gallon

Pump Load (HP) $ .80 $ .90 $ 1.00 $ 1.20 $ 1.40 $ 1.60
$.0 $..55. $.62 $.69 $ .82 $ .96 $1.10

20 1.10 1.23 1.37 1.65 1.92 2.19
30 1.65 1.85 2.06 2.47 2.88: 3.29
40 2.19 2.47 2.74 3.29 3.84 4.39
50 2.74 3.09 3.43 4.12 4.80 5.49
75 4.12 4.63 5.14 6.17 7.20 8.23
100 5.49 6.17 6.86 8.23 9.60 10.97
125 6.86 7.71 8.58 .10.29 12.00 13.71
150 8.24 9.26 10.29 12.35 14.40 16.46


Page 8




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