Chapter 11: Sprinkle Irrigation - NRCS Irrigation ToolBox Home Page

Hand-move lateral lines need to be limited to one
or two pipe sizes for simplicity of operation. The
trend in recent years has been toward the use of a
single pipe size.
Lateral lines should be located at right angles to
the prevailing wind direction where possible and
moved in the direction of the wind if the water contains
more than 1000 ppm of salts.
If lateral pipelines are to remain in a single design
area and are not to be moved from field to
field, they should be located so that they can be rotated
around the mainline, thereby minimizing the
hauling of pipe back to the starting point for subse.
quent irrigations (see fig. 11-29Ch
Farming operations and row directions often influence
the layout of laterals. Contoured row crops
can be sprinkle irrigated only with hand-move or
solid-set systems, which presents special problems
such as difficulty in placing and moving lateral
lines and getting uniform coverage.
Where the land is terraced and the topography
broken, curves in the alignment of the rows may be
sharper than can be turned with the limited deflection
angle of the coupling devices on portable irrigation
pipe. This difficulty may be overcome in the
following ways: soil profiles permitting, land grading
may be used to improve terrace and row alignment;
short lengths of flexible hose may be used in
the line at the sharpest bends. Some growers prefer
to run the laterals parallel and downhill on a slope
somewhat steeper than the grade of the terraces
even though both rows and terraces must be
crossed by the pipelines. In such cases, several
plants are removed or left out of each row at points
crossed by the lateral lines.
Where sloping land is terraced and the slopes are
not uniform, lateral lines laid between crop rows
will not be parallel, Thus the lateral spacing (s)
will be variable between two adjacent lines. This
variation adversely affects uniform application and
efficient water use. Where topography permits their
use, parallel terraces will help overcome this problem.
Stripcropping has been used effectively in overcoming
some of the difficulties arising from sprinkle
irrigation of contoured row crops. The row crops
are planted in strips equal in width to the lateral
spacing. The alternating strips are equal in width to
the lateral spacing at the mainline point of beginning
but may vary considerably in width at points
distant from the mainline. Laterals are laid on the
contour along the outside of the row-crop strips as
shown in figure 11-31A. In this method the hay
crops as well as khe row crop are irrigated. Advantages
of this procedure are uniform coverage on the
row-crop strips and the relative e6se of moving the
pipe on firmer footing and outside the areas of tall
crops, Disadvantages are nonuniform coverage on
the secondary hay crop and the necessity for carefully
laying out the strips before planting each crop.
r --'I2
SPACING Sm FROM EDGE OF STRIP
. . MEADOW STRIP -
--.>EL 3 -
.___ --Z
---
MEADOW STRIP - N~
_---- 1.- _---
Figure 1l-31.-Typical
areas.
B
sprinkler lateral layouts on stripcropped
When it is not desired to irrigate the hay crop,
part-circle sprinklers may be used to irrigate the
row crop alone or the row crop may be planted in
strips equal in width to some multiple of S, and
the laterals operated entirely within the row-crop
strips as shown in figure 11-31B. A disadvantage
is in having to move the pipe when the upper part
of the soil is saturated.
Perforated pipe laterals may be used when irrigating
low-growing crops such as small vegetables. In