• TABLE OF CONTENTS
HIDE
 Front Cover
 Table of Contents
 Introduction & Sprinkler irrigation...
 Surface irrigation systems
 Subirrigation (seepage) system...
 Microirrigation systems
 Summary
 Back Cover














Group Title: Circular Florida Cooperative Extension Service
Title: Florida irrigation systems
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 Material Information
Title: Florida irrigation systems
Series Title: Circular Florida Cooperative Extension Service
Physical Description: 13 p. : ill. ; 28 cm.
Language: English
Creator: Smajstrla, A. G ( Allen George )
Clark, Gary A
Publisher: Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida
Place of Publication: Gainesville
Publication Date: 1992
 Subjects
Subject: Irrigation -- Florida   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: Allen G. Smajstrla and Gary A. Clark.
General Note: Cover title.
General Note: "February 1992."
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Bibliographic ID: UF00014462
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 - AAA6895
ltuf - AJC9168
oclc - 25677567
alephbibnum - 001716769

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Table of Contents
    Front Cover
        Front Cover 1
        Front Cover 2
    Table of Contents
        Table of Contents 1
        Table of Contents 2
    Introduction & Sprinkler irrigation systems
        Page 1
        Page 2
        Page 3
        Page 4
        Page 5
        Page 6
    Surface irrigation systems
        Page 7
        Page 8
        Page 9
    Subirrigation (seepage) systems
        Page 10
    Microirrigation systems
        Page 11
        Page 12
    Summary
        Page 13
    Back Cover
        Page 14
Full Text




Fe~rary1992Cirular103


Florida Irrigation Systems







Allen G. Smajstrla and Gary A. Clark

















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


Februa-ry 1992


Circular 1035














































































*Allen G. Smajstria is a Professor, Agricultural Engineering Department, IFAS, University of Florida, Gainesville, FL, and Gary A.
Clark is an Associate Professor, IFAS Gulf Coast Research and Education Center, Bradenton, FL.








TABLE OF CONTENTS


Introduction ................................... .......... 1

Sprinkler irrigation systems ................. .............. 1
Multiple sprinkler systems ................. ............ .. .2
Portable sprinkler systems ............................ 2
Hand-moved systems ............................ 2
Tractor-moved systems ........................... 3
Self-moved systems ............................. .3
Side-wheel-roll sprinkler systems .................. 3
Side-move sprinkler systems ................... .. 3
Semi-permanent sprinkler systems ................... .. 3
Permanent sprinkler irrigation systems ................. 4
Solid set irrigation systems ................... .... .4
Self-propelled sprinkler irrigation systems ............. .4
Center pivot irrigation systems ................. .. .4
Lateral-move irrigation systems .................. 5
Single sprinkler (gun) irrigation systems ................... .6
Portable gun systems ........................... ... .6
Hand-moved portable guns ................... .... .6
Tractor-moved portable guns ................... ... .6
Self-propelled (traveling) gun systems .................. 6
Cable-tow traveling guns .......................... 7
Hose-reel traveling guns .......................... 7

Surface irrigation systems ............... .................... 7
Level systems ............................. ........ .... 8
Level furrows ................................ .... 8
Level borders .................. .... ............ 8
Basins ................................ ..... ....... 8
Graded system s ............................... ....... .8
Graded furrows ................. ................. 9
Contour furrows ................ ..... ........... 9
Corrugations .............................. ..........9
Graded borders .................................9.
Flooding .............................. ....... ..... 9

Subirrigation (seepage) systems ........................... 10
Constant water table systems .......................... 10
Fluctuating water table systems ................. ....... .11

Microirrigation systems .............. .......... ........... 11
Drip .................................... ........... 11
Spray (microsprinkler) .............................. . 12
Bubbler ................................. .......... 12
Line-source ............................ ............ 12


Summary .................. .......


........... ....... ... 13








Introduction
Irrigation is extensively used for crop production
in Florida. Currently, more than two million acres
of cropland are irrigated. Florida's large irrigated
acreage is due to low water-holding capacity soils
and nonuniform rainfall distributions, despite large
annual rainfall amounts. The high cash values of
many crops grown, and the sensitivity of yield and
quality to drought stress provide the economic in-
centives for irrigation.

Many different types of irrigation systems are
used in Florida. This occurs because of the great
variety of crops, the relative availability of water,
diverse hydrological conditions, the costs of differ-
ent systems, and the fact that all irrigation systems
are not adaptable to all types of crops and crop pro-
duction systems. Irrigation system selection is also
affected by soil type. The deep sandy ridge soils re-
quire water to be transported in pipes and pressur-
ized irrigation systems to be used, while the high
water table flatwoods and muck soils permit the
use of gravity-flow irrigation systems and open
ditches. Microirrigation systems are becoming in-
creasingly popular, especially in areas where peri-
odic water shortages have occurred. Sprinkler sys-
tems may be required for irrigation for freeze pro-
tection, transplant establishment, crop cooling, and
some field preparation procedures.

Irrigation systems can be grouped into four gen-
eral classes, all of which are in use in Florida. The
four classes are: (1) sprinkler, (2) surface, (3)
subirrigation (seepage), and (4) microirrigation.
Most Florida acreage (about 900,000 acres) is irri-
gated with seepage systems. Sprinkler systems
rank second, irrigating almost 600,000 acres.


Microirrigation systems (about 450,000 acres) are
the newest and most rapidly increasing type of sys-
tem. Only about 100,000 acres are surface (flood)
irrigated.


Sprinkler irrigation systems
Sprinkler irrigation systems are systems in
which water is applied by spraying it through the
air from nozzles mounted on pressurized pipelines.
Thus, water applications approximate rainfall, and
systems are designed to apply water uniformly over
the crop production area.

Sprinklers consist of nozzles mounted in a sprin-
kler body through which water is discharged under
pressure. Nozzles may either rotate or be fixed. Ro-
tating nozzles are typically impact-driven, gear-
driven, or driven by the reaction as the jet of water
is discharged. All of these methods use the energy
of the flowing water to make the system operate.
Individual sprinklers apply water to a circular or
part-circle pattern created by the nozzle rotation.
A typical impact sprinkler is shown in Fig. 1.

Fixed (spray) nozzle systems use a rigidly-
mounted nozzle which discharges against a deflec-
tor plate to distribute water (Fig. 2). Circular, part-
circle, square, or rectangular water application pat-
terns are possible, depending on the nozzle and de-
flector design.

Nozzle sizes for sprinkler irrigation vary widely.
Sizes range from very small (1/8-inch or smaller)
diameters which discharge only 1 to 2 gallons per
minute (gpm) to very large (over 1-inch) diameters
which discharge up to 1000 gpm.


Figure 1. Typical impact-type rotating sprinkler. Figure 2. Typical fixed nozzle (spray) Irrigation sprinkler.








Operating pressures also vary widely, ranging
from only 10 pounds per square inch (psi) to over
100 psi. Larger nozzles usually require larger oper-
ating pressures to provide sufficient energy for
proper water distribution.

Rotating nozzle sprinklers have much larger di-
ameters of coverage than fixed nozzle sprinklers.
As a result, they are most commonly used in large
field systems where it is desirable to uniformly dis-
tribute water over large areas with as few sprin-
klers as possible. Spray nozzles are used in appli-
cations where the diameters of coverage are not as
critical, such as small plot areas and in self-pro-
pelled irrigation systems (center pivots and linear
move systems) where the irrigation system travels
over the area to be irrigated.

Many types of sprinkler irrigation systems are in
use, ranging from small, portable manually-oper-
ated systems to large permanent, automatically-
operated systems. Sprinkler systems are classified
in the following sections of this circular, and typical
applications of each class are discussed.


Multiple sprinkler systems
Multiple sprinkler systems use many small
sprinklers with overlapping patterns. The amount
of overlap is critical to achieve high uniformity of
water application. Sprinklers are typically over-
lapped 50% to 60% of their diameters of coverage
under low wind (less than 5 mph) conditions.
Greater overlaps (and thus closer spacings) are re-
quired for higher wind speed conditions.

In multiple sprinkler systems, sprinklers are
mounted on a lateral pipe or network of lateral
pipes which carry water to the sprinklers. Water is
supplied to the laterals from manifold (header) or
main pipelines, depending on the system design.
Multiple sprinkler systems are classified as por-
table, semi-permanent, or permanent based on
whether the sprinklers and pipelines are moved
from location-to-location between irrigation sets or
whether the components are permanently buried in
the field.


Portable sprinkler systems
Portable sprinkler systems are systems in which
the sprinklers are mounted on movable lateral pipe
sections which are transported from one location to
another between irrigations (Fig. 3). The lateral
pipes and sprinklers are set up on the soil surface


Figure 3. Portable sprinkler irrigation system with impact
sprinklers installed on aluminum lateral pipelines.


and remain in place while irrigation occurs, then
they are moved to a new location (zone, or set) and
the process is repeated. These systems are typi-
cally designed with sufficient capacity to irrigate all
zones in time to be returned to the first zone before
plant water stress occurs. There are three types of
portable sprinkler systems based on the method
used to move the lateral pipes and sprinklers be-
tween irrigations: hand-moved, tractor-moved, and
self-moved.


Hand-moved systems
Portable, hand-moved sprinkler systems are
manually-moved from zone to zone. They consist of
sprinklers mounted on portable aluminum lateral
pipes, usually using short risers. Aluminum pipe is
used because it is strong, light-weight, resistant to
degradation by sunlight, and easily transported
and connected with quick-connect couplings. Short
risers are typically used because the laterals are
not firmly anchored, and tall risers tend to lean or
fall.

Laterals may be connected to portable aluminum
manifold and mainline pipes, which may also be
moved between sets. Buried PVC mainlines and
manifolds are sometimes installed, and lateral con-
nections are made through permanent hydrant
valves which bring the water to the surface. These
systems are sometimes called semi-permanent be-
cause the mainlines are permanently installed and
only the laterals are portable.

Portable hand-moved sprinkler systems are
widely used in Florida because they (1) have a low
initial cost, (2) are flexible, easily adapted to vari-



















Figure 4. Side-wheel-roll sprinkler system irrigating cabbage
transplants for establishment.

ous field shapes and sizes, and (3) can be moved
with many Florida vegetable crops which are ro-
tated from field-to-field to avoid disease problems
or on rented land. A limitation to the use of por-
table hand-moved systems is the large labor re-
quirements to move the pipe between zones. Be-
cause the pipes must be manually moved, these
systems are not adaptable to tall crops such as
corn, or other crops which would prohibit easily
moving the system.


Tractor-moved systems
Portable tractor-moved sprinkler systems consist
of sprinklers mounted on portable aluminum lat-
eral pipes which are rigidly connected and mounted
on wheels or skids. The laterals are towed between
zones by pulling from the ends of the laterals with
a tractor. These systems are more expensive than
portable hand-moved systems, but have lower labor
requirements. They are only used on short crops
which are not disturbed by the skids or tractor traf-
fic. These systems are most adaptable to larger
land areas (longer lateral lengths) than hand-
moved systems, or heavier soils than typical
Florida sands so that less frequent moves are re-
quired. Therefore, portable tractor-moved sprin-
kler systems are not often used in Florida.


Self-moved systems
Portable self-moved sprinkler systems consist of
sprinklers mounted on aluminum lateral pipes
which are mounted above the soil surface on wheels
(Fig. 4). They also contain the mechanical compo-
nents required to move the system, thus making
these systems more expensive than hand or tractor-
moved systems. There are 2 types of self-moved
sprinkler systems, classified by the method of
movement: (a) Side-wheel-roll, and (b) Side-move
sprinkler systems.


Side-wheel-roll sprinkler systems. These sys-
tems use laterals which serve as the axle for wheels
located along the length of the lateral. This system
is moved between sets by rotating the lateral pipe
(axle). The lateral pipe is typically rotated by a
chain drive system powered by a small gasoline-
powered engine located near the center of the lat-
eral. Sprinklers are kept in an upright position for
effective operation by means of a weighted swivel
coupling on each sprinkler.

Because the lateral pipe is mounted only 3-4 ft
above the soil surface, this system is only adaptable
to short crops. Few of these systems are used in
Florida. The most common applications are for
vegetables, short forage crops, and turf production.

Side-move sprinkler systems. These systems
use a lateral pipe mounted on a short A-frame 4-5
ft above the soil surface. Each A-frame is sup-
ported by 2 wheels, which are typically powered by
a chain-drive mechanism from a drive shaft that
runs parallel to the lateral pipe along the length of
the lateral. These systems are more expensive, but
have no appreciable advantages over side-wheel-
roll systems for Florida crop production systems.
Thus, they are not commonly used in Florida.


Semi-permanent sprinkler systems
A semi-permanent sprinkler irrigation system
(Fig. 5) is a system which is set up and left in place
throughout the crop growing season, after which it
is manually removed and stored for the next grow-
ing season. Components of the system, such as the
main or manifold pipelines are often permanently
installed. A type of semi-permanent multiple sprin-
kler irrigation system used in Florida is the solid
set system. Solid set systems are those in which the
laterals and sprinklers cover the entire field to be


Figure 5. Semi-permanent sprinkler system with portable lat-
erals fed from permanent underground pipelines.








irrigated, thus they do not need to be moved be-
tween irrigations.

The entire production area under a semi-perma-
nent solid set system is not necessarily irrigated at
once. In many cases, valves are used to control flow
to individual laterals or zones. In other cases, such
as when required for freeze protection, the entire
field may be irrigated at once. In both cases, labor
costs for system operation are low, because irriga-
tions are controlled simply by opening and closing
valves rather than by moving pipe.

Solid set, semi-permanent systems typically con-
sist of sprinklers mounted on portable aluminum
pipe. Because the entire production area is simulta-
neously covered with pipe and sprinklers, the ini-
tial system cost is much greater than the cost of a
portable sprinkler system. Field traffic problems
may also exist because the pipe remains in place on
the soil surface during the irrigation season. In
Florida, these irrigation systems are primarily used
for vegetable and sod production.


Permanent sprinkler irrigation systems
There are two types of permanent irrigation sys-
tems: solid set and self-propelled irrigation sys-
tems. Both types are commonly used in Florida.


Solid set irrigation systems
Permanent solid set irrigation systems are sys-
tems which consist of permanently placed pipes
and sprinklers. In Florida, lateral, manifold, and
mainline pipes are typically buried, and only the
sprinklers and risers extend above the ground sur-
face (Fig. 6). Because pipes and sprinklers are re-
quired to cover the entire production surface, per-
manent solid set systems are usually considerably
more expensive than other types of irrigation sys-
tems. Therefore, permanent systems are typically


Figure 6. Pipelines are buried In permanent solid set sprinkler
systems used for strawberry production.


Figure 7. Center pivot irrigation laterals are supported by large
A-frames with drive wheels for self-propelled operation.


used only on high cash value crops including citrus,
strawberries, ornamental ferns and other nursery
crops.

As with semi-permanent solid set systems, the
entire production area under a permanent solid set
system is not necessarily irrigated at once. Valves
are often used to control flow to individual zones.
However, when required for freeze protection, plant
establishment, or crop cooling, the entire field may
be irrigated at once. In both cases, labor costs for
system operation are low because water delivery to
a zone is controlled by simply opening and closing
valves rather than by moving pipe.


Self-propelled sprinkler irrigation systems
Self-propelled irrigation systems are those which
operate under their own power. During irrigation,
they move slowly and continuously across the field
as it is being irrigated. There are two types of self-
propelled multiple sprinkler irrigation systems
which are being manufactured: center pivot and
lateral-move systems.

Center pivot irrigation systems. These sys-
tems consist of sprinklers which are mounted on a
lateral pipe which is supported approximately 10-
12 ft above the ground by large A-frames (Fig. 7).
The lateral is fixed to a pivot point at one end. Wa-
ter is supplied at the pivot point. In most systems,
the lateral rotates around the pivot point and irri-
gates a circular or part-circle area in the center of a
square block of land (Fig. 8).

Most center pivot systems are equipped with a
large diameter end gun. The end gun operation is
normally limited to a 180-degree arc, and its appli-
cation is directed to areas beyond the lateral pipe-
























Figure 8. Center pivots irrigate circular (or part-circle) land
areas.


line. This extends the effective diameter of the irri-
gation lateral. In many systems, the end gun is op-
erated only in the corners of the square field, thus
increasing the acreage that can be irrigated.

Some center pivot systems are equipped with
corner units which operate only in the corners of a
square field to irrigate most of the square. Corner
units typically consist of one additional tower and
section of lateral pipeline which are extended for
irrigation of the corners of the field and retracted
along the sides of the field.

Because the laterals travel over the area to be
irrigated, center pivots can effectively use low pres-
sure spray nozzles to distribute water. When spray
nozzles are used, pumping costs are reduced, how-
ever, application rates are high because the water
is applied near the lateral rather than being dis-
tributed over a wide area. The high application
rates can cause runoff from soils with low infiltra-
tion rates. This is normally not a problem in
Florida because of the high infiltration rates of
typical sandy soils. Thus low pressure center pivot
systems equipped with spray nozzles are often used
in Florida.

Because of the height of the lateral, center pivot
systems are adaptable to most crops, including tall
crops like corn. The cost of a center pivot system
per acre irrigated decreases with increasing size up
to the common size of 160 acres. Thus center pivots
are often used to irrigate large acreages of lower
cash value crops such as field crops. They are also
adaptable to both small and large acreages of high
cash value crops, but irrigation schedules are not as
flexible as solid set system schedules. For example,


24 to 48 hours may be required to complete one
revolution of a center pivot system, and this time
may be excessive for shallow-rooted vegetable crops
grown on sandy soils.

Center pivot systems are more expensive than
portable systems, but less expensive than perma-
nent solid set systems. Because they are self-pro-
pelled, irrigations are easily scheduled and ad-
justed, and labor costs are low.

Center pivot systems are widely used for field
crop production throughout the world. They are
used for field crops in north Florida, and for sod,
forage crops, pasture, and waste disposal through-
out Florida.

Lateral-move irrigation systems. Lateral-
move irrigation systems are similar to center pivot
systems with the exception that the A-frame sup-
ported lateral pipe travels in a lateral (linear) di-
rection rather than pivoting around a central point
(Fig. 9). Thus, lateral-move systems are better
adapted to rectangular land areas than center
pivots.

Because lateral-move systems do not rotate
about a fixed pivot point, they must drag a large
flexible hose, use a permanent underground pipe-
line with risers modified for automatic operation, or
use an open ditch for the water supply. The hose-
drag units are the most common. The open ditch
systems require a pump to travel with the lateral
pipe to pressurize the water. Lined ditches would
be required in the deep sandy soil areas of Florida,
but unlined ditches could be used in the flatwoods
soil areas where high water tables exist. Perma-
nent underground pipe systems with automatic


Figure 9. Lateral-move irrigation systems irrigate rectangular
land areas. The pumping station travels with the lateral.








couplers are more technically complicated and ex-
pensive than the other methods of supplying water
to a lateral-move irrigation system.

Lateral-move irrigation systems are more expen-
sive than center pivots. Thus, these systems are
primarily used in areas where the value of land dic-
tates the use of systems which are adapted to rect-
angular land areas, and for irrigation of very large
land areas so that the cost per acre is lower. Lat-
eral-move systems are not commonly used in
Florida.


Single sprinkler (gun) irrigation
systems
Gun sprinklers are very large sprinklers which
operate at high pressures (Fig. 10). Nozzle sizes
commonly range to over 1-inch in diameter. Pres-
sures required for proper operation typically range
from 80 to 120 psi, with 100 psi being very common.
While flow rates may range up to 1000 gpm for very
large guns, rates of 500 to 600 gpm are very com-
mon for large field scale guns. Typically only one or
two guns are used in a gun irrigation system.

Gun irrigation systems require large energy in-
puts per unit of water delivered because of their
high operating pressures. They also have relatively
high labor requirements, both to move the portable
guns between sets and to set up the self-propelled
(traveling) guns. Despite these limitations, gun
systems are popular in Florida. They are flexible,
that is, they allow irrigation of oddly-shaped fields,
they are available in a range of sizes to permit irri-
gation of small to relatively large (up to 90 acres


U .- -,

-Th -


Figure 10. Gun sprinklers use large diameter nozzles to dis-
charge high flow rates at high pressures.


Figure 11. Portable gun system for field crop irrigation in
north Florida.


per gun) areas, and they are easily transported be-
tween fields. Guns also have relatively low initial
costs as compared to permanent or portable solid set
irrigation systems, and they require less labor than
portable multi-sprinkler systems.


Portable gun systems
Portable gun irrigation systems (Fig. 11) are
widely used in Florida. Guns may be moved by
hand, but due to their size, they are typically towed
with tractors.


Hand-moved portable guns
Hand-moved portable guns have larger labor re-
quirements than other types of guns because they
must be manually moved between sets, and a gun is
a relatively large item of equipment. Hand-moved
guns are most adaptable to relatively small acre-
ages. They are commonly used to irrigate small
fields of vegetables, melons, and tobacco, especially
in north Florida. Water for hand-moved portable
guns is typically supplied by either portable alumi-
num pipe or large diameter flexible hoses.


Tractor-moved portable guns
Tractor-moved guns are mounted on skids or
wheels to facilitate moving them between sets. Less
labor is required, thus permitting them to be used on
larger acreages than hand-moved guns.


Self-propelled (traveling) gun systems
Traveling guns are widely used in Florida. These
are self-propelled irrigation systems. Two types of






















Figure 12. A cable-tow traveling gun pulls itself through the
field by winding up a cable anchored at the edge of the field.


traveling gun systems are in common use. They
both use the same types of guns for water distribu-
tion, but they are different with respect to the way
the guns are moved through the field. With both
systems the guns are mounted on carts or trailers
that are slowly and continuously moved through
the field as the guns operate. The rate of water ap-
plication and total depth applied depend on the
flow rate from the gun, the diameter of coverage,
and the speed at which the gun travels.


Cable-tow traveling guns
Cable-tow systems automatically tow a large gun
through the field by winding up a cable (Fig. 12).
The gun is mounted on a cart which also contains a
cable reel and winch. The cable is stretched across
the field in the desired direction of travel, and the
end of the cable is firmly anchored at the end of the
travel lane. As water flows to the gun, an impeller
drive unit or water piston is used to power the
winch. Thus, the cable-tow traveling gun pulls it-
self across the field by winding up the cable. The
speed of travel is adjustable from only a few feet
per minute (fpm) to 10 or more fpm. Water is sup-
plied to the gun by a collapsible, flexible hose that
is also towed by the system. A travel lane approxi-
mately 10 ft wide is required for this type of travel-
ing gun because the flexible hose loops behind the
cart.

Because they are set up to irrigate long travel
lanes, cable-tow systems require much less labor
than portable guns. Travel lane lengths of up to
1320 ft are typical. A typical 500 gpm cable-tow
traveling gun can irrigate up to 80 acres.

. Despite the high cost of gun operation, cable-tow
systems are commonly used to irrigate field crops,


J.


Figure 13. A hose-reel traveling gun winds up the hose on a
large reel to move the gun during Irrigation.


j6 A,^


vegetables, melons, and citrus in Florida. They are
widely used throughout the state, although their
high operating costs have caused some systems to be
replaced by more energy-efficient microirrigation sys-
tems, especially for perennial crops such as citrus.


Hose-reel traveling guns
A hose-reel traveling gun uses a large reel unit to
wind up the hose and retract the gun (Fig. 13). The
hose is semi-rigid and does not collapse on the reel,
so that water can be continuously pumped through it
during operation. The hose and gun are laid out in
the desired direction of travel. The reel is then used
to retract the hose and gun at slow speeds, irrigating
as the gun is retracted.

Hose-reel systems require less labor than cable-
tow systems because they are easier to set up for op-
eration. A typical 500 gpm hose-reel traveling gun
can irrigate up to 90 acres. However, these systems
are more expensive than cable-tow systems, thus
they have not displaced all cable-tow systems.

Hose-reel systems are used for the same crops as
cable-tow gun systems. In addition, there is some
use of hose-reel systems for the establishment of
transplanted vegetable crops. The smaller cart on
which the hose-reel gun is mounted permits use in
row crops without the need for a wide travel lane to
tow the hose behind the gun.


Surface irrigation systems
Surface irrigation systems are those in which wa-
ter is applied on the soil surface and is distributed








across the surface by the soil hydraulic characteris-
tics or by flooding the entire area to be irrigated.
Surface irrigation is primarily applicable on
heavier clay and loam soils which have finer tex-
tural classifications and lower hydraulic conductivi-
ties than typical Florida sandy soils. Where such
heavy soils exist in Florida (primarily in north
Florida, near Georgia and Alabama), irrigation is
not generally practiced because of the high water-
holding capacities of these soils and Florida's large
annual rainfall. Thus, except for rice flood irriga-
tion systems and citrus crown flood systems, sur-
face irrigation is not commonly used in Florida.


Level systems
Level surface irrigation systems are those in
which the soil surface is essentially level and the
water moves across the surface primarily due to the
difference in water depths. These systems are irri-
gated by applying water at high rates across the
soil surface to wet the surface as quickly as pos-
sible, and then continuing to apply water at re-
duced rates while infiltration occurs simulta-
neously across the entire field being irrigated. The
water is applied and then allowed to stand and in-
filtrate until all of that applied has infiltrated.
Normally several inches (2 to 6 inches) are applied
per irrigation.


Level furrows
Level furrows are used in row crop production
systems. Crops are planted on beds and water is
directed into the furrows, normally into each or ev-
ery other furrow. Water is typically applied by si-


Figure 14. Field ditches are flooded with water for crown flood
Irrigation of citrus.


phon tubes from open ditches or by gates or valves
from gated aluminum pipes.

In Florida, a type of level furrow irrigation sys-
tem is used to irrigate bedded citrus on flatwoods
(high water table) soils. This "crown flood" irrigated
citrus is irrigated by allowing water inflow to large
furrows between the citrus beds (Fig. 14), allowing
the water to stand in the furrows for 8 to 24 hours,
and then draining the furrows by pumping the wa-
ter to the next citrus grove. In these systems, wa-
ter is applied through large diameter conduits from
a large manifold or header ditch.


Level borders
Borders are typically rectangular blocks of land
bordered by soil ridges (levees or borders) 1 to 2 ft
high. The borders retain the water applied within
the area to be irrigated. Water is typically applied
by large gates from open ditches, portable gated
pipe, or valves from underground pipelines. Less
frequently, siphon tubes are used in open ditches.

Rice irrigation systems are the only level border
surface irrigation system used in Florida (Fig. 15).
Levees (borders) maintain water depths in each
paddy (border) within about 1 inch of the average
depth. Water levels are maintained above the soil
surface to flood the area for weed control. Water
levels in each paddy are maintained by drop struc-
tures or weirs which are set at the required water
elevation. Runoff from each paddy flows into the
next downstream paddy.


Basins
Basins are small border areas, primarily used for
permanent crops such as orchards or vineyards, but
also used for some ornamental crops. Basins may
encompass only one or several trees or other plants.
Irrigation may be applied by risers from under-
ground pipelines into individual basins, or by any
of the other methods discussed for level border sys-
tems.


Graded systems
Graded surface irrigation systems are those in
which the field slope is large enough that it signifi-
cantly influences the way that water must be man-
aged to obtain uniform water applications. Graded
systems are typically irrigated by initially applying
water at high rates to wet the entire surface, then
reducing the application rate or pulsing the appli-





















Figure 15. Rice production systems are flooded for irrigation,
weed control, and to prevent oxidation of muck soils.


cations to closely approximate the soil infiltration
rate. Large amounts of runoff may occur if slopes
are steep.

Land smoothing is typically required to obtain
high efficiencies from graded surface irrigation sys-
tems. Other techniques used to obtain high irriga-
tion efficiencies are tailwater recovery (re-use or
recycling), cablegation (an automated flow rate cut-
back irrigation method), and surge irrigation
(where several separate pulses of water rather than
continuous applications are used).


Graded furrows
Graded furrows are irrigated with the same
equipment as level furrows. In order to obtain uni-
form water applications along the furrow without
excessive runoff, cut-back irrigation is practiced. In
cut-back irrigation, the flow rate is reduced to the
rate required for infiltration after the water
reaches the distant end of the furrow.


Contour furrows
A contour furrow has a gradient to allow runoff
from rainfall to flow nonerosively from the field
site. Irrigation management is similar to the man-
agement of graded furrows. However, more labor is
typically required to avoid erosion and nonuniform
water application which might occur if furrows
overflow during irrigation.


Corrugations
Corrugations are small furrows which are
formed when small grain seeds are drill-planted.
Management of the irrigation of corrugated fields is
similar to the management of graded furrows.


However, irrigation of corrugated fields is more dif-
ficult and labor-intensive than that of conventional
furrows because it is difficult to prevent these small
furrows from overflowing.


Graded borders
Graded borders retain irrigation water within
the border areas because the ridges constructed are
typically 1 to 2 ft tall. However, if rapid surface
wetting followed by reduced (cut-back) flow rates
are not used, the uniformity of water application
will be reduced. If cut-back irrigation is not accu-
rately practiced, excess water will accumulate and
infiltrate at the lower ends of the borders, and thus
the efficiency of these systems will be reduced.


Flooding
The term "flooding" is used to describe three dis-
tinctly different types of irrigation practices: (1) in
many parts of the world, flooding refers to the irri-
gation of heavy soils where furrows, corrugations,
or borders do not exist to direct water uniformly
across the surface, (2) this term is also widely used
to describe the practice of inundating the soil sur-
face in rice production systems, and (3) in Florida,
the term "crown flood" is used to refer to a citrus
irrigation method that was previously discussed in
the "level furrow" section of this publication.

Flooding is often practiced where water supplies
are plentiful and inexpensive, so that irrigation ef-
ficiency is not the major concern, although irriga-
tion efficiencies can be relatively high, depending
on soil properties and whether tailwater is re-used.


Figure 16. Seepage irrigation of sandy soils uses water fur-
rows to distribute water for tomato production.









-.-- &... __~


Figure 17. Muck soils are seepage irrigation with widely
spaced surface ditches for sugarcane production.

In Florida, both rice and citrus are irrigated with
flood irrigation systems. Rice is produced on high
water table organic soils which must also be flooded
for another purpose, to prevent oxidation and loss of
the organic soil. When citrus is produced using the
crown flood method, runoff water is typically used to
irrigate another citrus grove in a large management
area, thus the overall efficiency of water use is high.


Subirrigation (seepage) systems
Subirrigation (seepage) systems are those in
which water is supplied at rates high enough to es-
tablish and maintain a water table just beneath the
crop root zone. Irrigation then occurs by capillary
movement of water into the crop root zone. This
method of irrigation is limited to use on sandy (Fig.
16) and muck (Fig. 17) soils with high hydraulic
conductivities in the surface soil layers, but with re-
strictive subsurface layers and existing high water
tables. Large quantities of water must also be
available to raise the water tables in addition to
providing water for crop evapotranspiration (ET).

Water is typically applied from a parallel network
of open field ditches (water furrows) or underground
pipe (drain tiles), called laterals. Open ditches are
more common because underground pipe systems
are more expensive, and they are sometimes clogged
by bacterial activity, chemical precipitation, and
other causes. The ditches are also required for sur-
face drainage during large rainfall events. Re-
cently, subsurface drip irrigation systems have been
developed for water table control (Fig. 18). Al-
though they are more expensive and have higher
maintenance requirements than open ditches, they
conserve water by avoiding runoff and standing wa-
ter in ditches, and they allow more precise water
table control through the network of underground


pipelines. Thus, these systems are primarily being
installed in areas where water shortages exist.

Lateral ditches are typically spaced from 12 to 60
ft apart on sandy soils, depending on the soil hydrau-
lic conductivity and on irrigation, drainage, cultural,
and field equipment requirements. On muck soils,
ditches are often wider spaced, typically from 100 to
200 ft, because of the greater conductivity of these
soils.


Constant water table systems
Constant water table systems are systems in which
irrigation water is applied continuously (except dur-
ing, or in anticipation of rainfall) to maintain a water
table at the height required for optimum crop growth.
Water is continuously pumped into ditches or water
furrows, and water levels are typically controlled with
flashboard riser structures at the downstream end of
the irrigated field. Flow rates are often adjusted as a
function of stage of crop growth, time of year, and in
some cases, even time of day. Diurnal field water
tables typically fluctuate only a few inches in re-
sponse to changes in ET rates during the day.

Constant water table seepage systems are used to
irrigate large acreages of vegetables and sugarcane,
and some citrus in Florida. Depending on field slope,
soil properties, ET rates, and management practices,
runoff often occurs from the fields. Irrigation efficien-
cies are lowest when runoff water is discharged from
the irrigated field. Efficiencies are highest when run-
off is recycled or applied to other irrigated fields and
when application rates are matched to changes in wa-
ter requirements during each day.


Figure 18. Water tables are controlled for Irrigation without
runoff using subsurface drip irrigation laterals.





































Figure 19. Spaghetti tube drip emitters are used to apply water
to each individual container in this ornamental nursery.


Fluctuating water table systems
Fluctuating water table seepage irrigation sys-
tems are systems in which water tables are permit-
ted to fluctuate on a daily basis as water is only ap-
plied intermittently in an effort to reduce runoff.
These systems shut off irrigation pumps when water
tables are high and runoff begins to occur. Pumps
are re-started when water tables drop to critical lev-
els, or during peak ET times of the day.

Fluctuating water table systems are less fre-
quently used than constant water table systems be-
cause higher levels of management are required, the
potential for leaching crop nutrients is increased,
and yield reductions occur when water tables fluctu-
ate excessively.


Microirrigation systems
Microirrigation systems are those which use low
flow rate emitting devices (emitters) to place water
on the soil surface near the plants being irrigated or
below the surface directly into the plant root zone.


Microirrigation systems are characterized by the use
of small diameter, flexible plastic lateral pipes and
operation at low pressures. Normally only a fraction
of the crop root zone is irrigated, and frequent, small
irrigations, which keep the irrigated zone near field
capacity, are practiced. Chemicals, especially fertil-
izers and cleaning agents, are often applied through
microirrigation systems.

The term "microirrigation" is a general term
which includes several specific types of systems, in-
cluding drip, spray (or microsprinkler), bubbler, line
source perforated pipes or seepage hoses, or other
similar types of systems. With microirrigation, the
levels of management, water treatment, and filtra-
tion generally exceed those associated with other
types of irrigation systems.


Drip
Drip types of microirrigation systems apply water
from discrete point source emitters attached to or
molded into lateral pipes (Fig. 19). Emitter dis-
charges are in the form of small streams or indi-
vidual drops, with flow rates ranging from 0.3 to 2
gph, but most commonly being 1 gph. Operating
pressures typically range from 6 to 30 psi.

In Florida, drip irrigation systems are primarily
used in vegetable (especially tomato and pepper),
ornamental (container nurseries), and fruit crop (cit-
rus) production systems. Because of system costs,
they are not used in agronomic (field) crops.

Emitters are typically placed on or slightly below
the soil surface or under the plastic mulch in


Figure 20. Spray (microsprinkler) emitters irrigate a large frac-
tion of the tree root zone in this citrus production system.








mulched vegetable production systems. Because
drip emitters rely on the soil hydraulic properties to
distribute water, and typical Florida sandy soils
limit lateral unsaturated water movement, spray (or
microsprinkler) emitters have become more popular
in those tree crop production systems where it is de-
sirable to irrigate a significant fraction of the tree
root zone with relatively few emitters.


Spray (microsprinkler)
Spray or microsprinkler types of microirrigation
systems, like drip systems, emit water at discrete
points. However, emitters typically have flow rates
much greater than drip emitters. Flow rates nor-
mally range from 8 to 30 gph, with 15 to 20 gph
emitters being very common. Spray emitters dis-
tribute water by spraying it through the air over di-
ameters of 5 to 25 ft, depending on the crop being
irrigated. Emitters are typically mounted on short
(6 to 12-inch) risers above the ground surface to im-
prove distribution patterns.

Spray emitters are most commonly used in citrus
microirrigation systems (Fig. 20). In citrus, the ad-
vantage of distributing water over a large diameter
as compared to the much smaller diameter of drip
emitters has been demonstrated to increase yields.
The larger flow rates and orifice sizes also reduce
filtration requirements and clogging problems.

Both spinners and fixed deflectors are used to dis-
tribute the water from spray emitters. The fixed de-
flector type are more often used because the moving
parts in spinner emitters sometimes fail to function
under field conditions.


14W 416


Figure 21. Bubblers have high flow rates and require sc
means of containing the water to prevent runoff.


Figure 22. Line-source microirrigation systems require a lat-
eral under the plastic mulch of each crop row for tomato pro-
duction.


Bubbler
Bubblers are relatively large flow rate
microirrigation emitters (Fig. 21). Flow rates are
typically 1-gpm or greater. Because of the high
flow rates, relatively large orifice sizes are used,
and clogging is typically not a problem, even with-
out filtration. However, the high flow rates may
result in runoff rather than infiltration into the
soil. Thus, bubbler systems are typically only used
in containers such as large ornamental planters or
in individual tree basins, which retain the water
and prevent runoff. Also, bubblers are typically op-
erated only a few minutes per irrigation, because
the required water volumes can be applied in a
short period of time.


Line-source


Line-source microirrigation systems use laterals
S with very closely spaced emitters, or either perfo-
rated or porous tubing are used rather than dis-
crete emitters. Water is emitted either continu-
ously along the lateral lengths, or at close intervals
so that the wetting patterns overlap and approxi-
mate that of a continuous line source.

Line-source tubing laterals are used in Florida
vegetable, strawberry and ornamental (bedded
flower) production systems (Fig. 22). These are
S typically thin-walled tubing of the disposable, lay-
flat type that have perforations or emitters molded
into the tubes at 6 to 24-inch intervals along their
lengths. Because of the limited water movement
for typical sandy soils, 8 to 12-inch spacings are
ome commonly used.
























Figure 23. Installation of line-source porous pipe
microirrigation laterals for subsurface irrigation of a small turf
plot.


Another common application of line-source tub-
ing is porous tubing which is buried or placed un-
der mulch in turf and landscape irrigation systems
(Fig. 23). Buried porous tubing can be used to
avoid overspray of water from roadway medium
strips and other turf areas where the sprayed water
might cause an inconvenience or hazard.


Summary
Irrigation is extensively practiced in Florida be-
cause of typical low water-holding capacity sandy
soils, nonuniform rainfall distributions, and sensi-
tivity to drought stress of the many high cash value
crops grown. Irrigation systems can be classified as
sprinkler, surface, subirrigation (seepage), and
microirrigation. Irrigation system characteristics,
applications, advantages and limitations were pre-
sented for systems in each of these classes, with
emphasis on systems commonly used in Florida.
The choice of an irrigation system for a specific ap-
plication requires careful consideration of econom-
ics, yield potential, water supply quantity and qual-
ity, soil, crop and cultural characteristics, design
limitations and management, maintenance and la-
bor requirements.
















































































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. Printed 2/92.




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