Em4885 irrigation management practices to protect ground water

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CHAPTER 4
Description
The term “dual irrigation systems” may be applied to a number of situations. Casual
observations or a formal irrigation system evaluation (IP 2.01.03) may indicate that the
one irrigation system in use is very inefficient at certain times in the season due to soil,
crop, or climatic conditions. Thus, another type of irrigation system, or a temporary
modification to the current system may be in order during these periods. Two of the
more common situations would be:
1. A hand-line or solid-set sprinkle system and a furrow/rill or border strip system used
on the same field in the same season. In this case the sprinkler system is used for
pre-irrigations, germination, and possibly early, light, seasonal irrigations. Sprinkle
systems allow better control of the total water application. This may be required by
the frequent, light applications during germination. Also, some soils will have very
high infiltration rates early in a season. The sprinkle system maintains high
application efficiency in a situation where total water applications would be hard
to control with the furrow/rill system.
2. Temporary use of portable gated pipe to reduce the run length of a furrow/rill
irrigation system. Again, when soil infiltration rates are high, or smaller water
applications are required, shorter furrow lengths make it easier to maintain
acceptable application efficiencies.
In both of the situations described above, the portable pipe, either sprinkler or gated pipe,
is removed at some time during the season and irrigations are continued using the regular
furrow/rill or border strip system.
IP 2.01.08 - Consider Changing the Irrigation System Type
Objective
Ensure that an appropriate irrigation system type, enabling sufficiently good application
efficiency, has been chosen for the site.
Description
An irrigation system is only as good as the management of that system. However, some
system types are more adapted to a particular situation than others. It may be that site
conditions will prevent good irrigation performance with one irrigation system type.
For example, it may be difficult to irrigate efficiently with furrows on a steep, rocky soil.
Or, excessive wind conditions will place a limit on potential efficiency with sprinkle
systems. In such cases consideration should be given to changing the irrigation system
type. The final decision should be based on a complete economic analysis.
It can be a difficult and expensive decision to change system types. The current irrigation
system operation should be evaluated first to see if there are changes that could be made to
improve performance (IP 2.01.03). If performance is poor, even with the best management
possible, other systems should be evaluated for adaptability.