Chapter 11: Sprinkle Irrigation - NRCS Irrigation ToolBox Home Page

Side-roll laterals up ta 1,600 ft long are satisfactory
for use on close-planted crops and smooth
topography. For rough or steep topography and for
row crops with deep furrows, such as potatoes,
laterals up to onemfourth mile long are recommended.
Typically, 4- or 5-in-diameter aluminum
tubing is used. For a standard quarter-mile lateral
on a close-spaced crop at least 3 lengths of pipe to
either side of a center power unit should be 0.072-in
heavy walled aluminum tubing. For longer lines and
in deep-furrowed row crops or on steep topography
more heavy walled tubing should be used, enabling
the laterals to roll more smoothly and uniformly
and with less chance of breaking.
A well designed side-roll lateral should have quick
drains at each coupler. All sprinklers should be pro*
vided with a self leveler so that regardless of the
position at which the lateral pipe is stopped each
sprinkler will be upright. In addition the lateral
should be provided with at least two wind braces,
one on either side of the power mover, and with a
flexible or telescoping section to connect the lateral
to the mainline hydrant valves.
Trail tubes or tag lines are sometimes added to
heavy walled 5-in side-roll lines. With sprinklers
mounted along the trail tubes the system has the
capacity to irrigate more land than the conventional
side-roll laterals. Special couplers with a rotating
section are needed so the lateral can be rolled forward.
Quick couplers are also required at the end of
each trail tube so they can be detached when a
lateral reaches its last operating position. The
lateral must be rolled back to the starting location
where the trail tubes are, then reattached far the
beginning of a new irrigation cycle.
Side-Move Lateral
Side-move laterals are moved periodically across
the field in a manner similar to side-roll laterals. An
important difference is that the pipeline is carried
above the wheels on small "A" frames instead of
serving as the axle. Typically, the pipe is carried 5
ft above the ground and the wheel carriages are
spaced 50 ft apart. A trail tube with 11 sprinklers
mounted at 30-ft intervals is pulled behind each
wheel carriage, Thus, the system wets a strip 320 ft
wide, allowing a quarter-mile long line to irrigate
pproximately 11 acres at a setting. This system
roduces high uniformity and low application rates.
Side-move lateral systems are suitable for most
field and vegetable crops, For field corn, however,
the trail tubes cannot be used, and the "A" frames
must be extended to provide a minimum ground
clearance of 7 ft. Small (60 to 100 gpm) gun sprinklers
mounted at every other carriage will irrigate a
150-ft-wide strip, and a quarter-mile-long lateral can
irrigate 4.5 acres per setting. Application rates,
however, are relatively high (approximately 0.5 iph),
The job of moving a hand-move system requires
more than twice the amount of time per irrigated
acre and is not nearly as easy as the job of moving
an end-tow, side-roll, or side-move system, A major
inconvenience of these mechanical move systems occurs,
however, when the laterals reach the end of an
irrigation cycle. When this happens with a handmove
system, the laterals at the field boundaries
can be disassembled, loaded on a trailer, and hauled
to the starting position at the opposite boundary.
Unfortunately, the mechanical move laterals cannot
be readily disassembled; therefore, each one must
be deadheaded back to its starting position. This
operation is quite time consuming, especially where
trail tubes are involved.
Fixed Sprinkler
A fixed-sprinkler system has enough lateral pipe
and sprinkler heads so that none of the laterals
need to be moved for irrigation purposes after being
placed in the field. Thus to irrigate the field the
sprinklers only need to be cycled on and off, The
three main types of fixed systems are those with
solid-set portable hand-move laterals (fig. 11-4),
buried or permanent laterals, and sequencing valve
laterals. Most fixed sprinkler systems have small
sprinklers spaced 30 to 80 ft apart, but some systems
use small gun sprinklers spaced 100 to 160 ft
apart.
Solid-Set Portable
Solid-set portable systems are used for potatoes
and other high-value crops where the system can be
moved from field to field as the crop rotation or
irrigation plan for the farm is changed. These systems
are also maved from field to field to germinate
such crops as lettuce, which are then furrow irrigated.
Moving the laterals into and out of the field
requires much labor, although this requirement can
be reduced by the use of special trailers on which
the portable lateral pipe can be stacked by hand.
After a trailer has been properly loaded, the pipe is
banded in several places to form a bundle that is
lifted off the trailer at the farm storage yard with a