Irrigation Methods
Border Irrigation Method
This is an old irrigation method that is relatively new in
Arkansas. The concept is to flush a large volume of water over a relatively flat
field surface in a short period of time. Borders are raised beds or levees
constructed in the direction of the field’s slope. The idea is to release water
into the area between the borders at the high end of the field. The borders
guide the water down the slope as a shallow sheet that spreads out uniformly
between the borders.
Most of the border irrigation in Arkansas has been used for soybean irrigation.
Border irrigation is best suited for precision graded fields
that have slope in only one direction. The crop should be flat planted in
the direction of the field slope or possibly at a slight angle to the slope.
Planting across the slope tends to restrict the water flow, especially on fields
with less than 0.1 ft. fall per 100 feet. Fields with slope in two directions
are not as well suited to border irrigation, but it may still be possible if the
borders spacing is relatively narrow.
The spacing between borders is dependent on soil type, field
slope, pumping capacity, field length and field width. A clay soil that cracks
is sometimes difficult to irrigate, but with borders the cracking actually helps
as a distribution system between the borders. This factor also makes it possible
to use borders on clay fields that have a slight side or cross slope. The
tendency on fields with side slope is for the water to flow to the lower side
and not spread out uniformly between the borders. The soil cracks lessen this
effect because the water will spread laterally as it follows the cracking
pattern. The border spacing on clay soil will generally be between 200 and 300
feet with the narrower spacing on fields with side slope.
The border spacing on sandy and silt loam soils that tend to
seal or crust over is more of a challenge than with the cracking clays. Side
slope on these soils results in the border spacing having to be narrower in
order for the water to spread uniformly between the borders. The border spacing
on these soils will generally range between 100 and 200 feet with the narrower
spacing on fields that have side slopes.
The pumping capacity and field dimensions (length and width) are
used to determine the number of borders needed and how many can be irrigated in
a reasonable time. Calculations can be made to estimate the time required to
irrigate a border, and it is usually possible to work toward approximately
12-hour set times. The 12-hour time set is very desirable because it fits very
well for managing water and labor. The border can be constructed in a variety of
ways and with different types of equipment. The method used is partially
determined by whether or not the crop is to be grown on the border. A settled
border height of 2 to 4 inches is all that is needed on ideal fields with no
side slope, but a 4- to 6-inch settled height is required if the field has side
slope or if the field has potholes. If the border is constructed with a
disk-type implement, an effort must be made to fill the ditch left at the base
of the border so it will not act as a drain furrow. The borders need to stop
at least 30 feet from the low end of the field so they will not restrict
drainage.
The water can be delivered into the area between the borders
from a canal, gated pipe or gated irrigation tubing. If irrigation tubing is
used, it is recommended that it be the heavier 9- to 10-mil tubing. The 2
1/2-inch plastic gates that deliver 65 to 75 gpm each can be installed in the
tubing, reducing the number of holes needed and simplifying closing gates at the
end of a set.
If border irrigation can be used on a field that is usually
flood irrigated, then it can provide certain advantages:
1. Less production area lost with border than with levees.
2. Improved ability to irrigate crops when it is small.
3. Don’t have to repair or rebuild border between irrigations,
thus a potential for time and labor savings.
4. Field drainage is not restricted by borders.
5. There is better possibility of growing crops on the border.
Border irrigation will not work on all fields and is not
necessarily a better method where the crop is already grown on good beds and
furrow irrigated. However, if a grower wants to move toward flat planting and
reduced tillage on these fields, then border irrigation may be more appealing
than flood. There is not adequate space in this publication to cover all of the
details associated with border irrigation. However, more information is
available through your local county Extension office.
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Methods
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