| It's difficult
to predict this early in the spring the type of weather we
will have come time for planting sugarbeets. What starts
out to be a spring with adequate rainfall and good soil
water content can easily change. Drying winds can quickly
remove soil water in the top 6 inches of soil, especially
if the soil has been left loose following spring tillage.
Inverting soil several times with pre-plant tillage
operations to create a good seed bed can also leave the
soil too dry for germination and emergence. Regardless of
the cause, less than adequate soil water means irrigation
may be necessary for establishing your crop of sugarbeets.
Center pivot operators may not view this as a major
problem. If spring precipitation is not enough to
compensate for dry soil conditions, a little water can
always be added with the center pivot. This follows the
general attitude that getting a better stand of sugarbeets
is easier if using a center pivot sprinkler system. Yet
during 1999, the University of Nebraska conducted a multi
state trial on cooperators fields in Nebraska, Colorado
and Wyoming. As a part of this study, emergence was
measured from a number of different field conditions. What
was observed in many cases was, that better emergence
resulted in furrow irrigated fields or fields that
required no irrigation after planting as compared to
fields that were irrigated using a center pivot.
This does not mean emergence is less because a center
pivot system is used, what it means is that irrigation
management for optimum sugarbeet emergence using a center
pivot should be based on meeting the needs of an emerging
crop, not on the convenience of using the irrigation
system. To be sure there is adequate water available for
emergence, the top foot of the soil profile should be at
or slightly below field capacity. This will supply the
emerging seedling with plenty of water for initial growth.
Remember, it's critical that seedling germination, once
started, not be slowed or interrupted by dry soil
conditions.
If using a center pivot system and soil conditions are
dry and germination is going to be questionable, consider
irrigating before planting to apply a portion of the water
needed.
Irrigate after all but perhaps the last tillage
operation before planting. This way a better estimate can
be made regarding total irrigation requirement. By meeting
crop water needs through a pre-plant irrigation, seed can
be planted directly into a firm and moist seed bed. This
seed bed, compared to soil that is dry and loose, allows
better seed depth control with the planter. As long as
there is no precipitation, the top 1/4 inch of the soil
surface remains loose which provides a buffer to reduce
wind erosion, reduce evaporation and allow seedlings to
emerge faster and easier.
If irrigating after planting to meet crop water needs,
light applications, approximately 0.3 inch or less are
often used and can result in half or more of the water
lost to evaporation within a one to two day period. If
this amount is not sufficient, a second irrigation is
needed immediately followed by perhaps a third or fourth
irrigation. With each irrigation, the structure of the
soil on the surface is broken down into a layer of
consolidated fine soil particles. This consolidated layer
of soil coupled with warm sunshine and wind can result in
varying levels of soil crusting. Even a small level of
soil crusting impedes seedling emergence and increases the
possibility of soil erosion. To counteract wind erosion,
the surface is roughened which increases evaporation of
water from the soil, and the cycle continues.
Regardless of whether irrigation is before or after
planting, apply enough water to meet crop needs using as
few of passes with the sprinkler system as possible. If
extreme dry conditions exist, pre-plant irrigation can
limit the number of after planting irrigations that create
less than desirable conditions for seed emergence. |