Em4885 irrigation management practices to protect ground water

IP 2.04.01 - Consult Experienced Agronomists/Engineers to Ensure
that the Appropriate Volume of Soil is Being Wet by the System Design
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CHAPTER 4
Objective
Ensure correct volume and pattern of soil wetting to minimize surface runoff and deep
percolation. This will also increase fertilizer-use efficiency. Note that the primary benefit
will be to ensure proper crop development.
Description
A major defining characteristic of micro-irrigation systems is that not all of the soil volume
in a field is wet. An important agronomic consideration when designing micro systems is
how much of the root zone should be wet to ensure proper crop development. The correct
volume of water may be delivered to the plant. But if the correct volume of soil is not
wet, or not wet in the correct pattern, crop development may suffer. And, there may be
surface runoff or excess deep percolation if water is too concentrated. Crop development
could suffer also, which would reduce fertilizer-use efficiency or leave the crop susceptible
to insects or disease. This, in turn, could require increased pesticide applications.
IP 2.04.02 - Have a Competent and Experienced Irrigation Engineer/Specialist
Check the Design for Emission Uniformity (pressure uniformity, correct
pressure for the device) - Use Pressure Regulators and Pressure
Compensating Emitters as Necessary
Objective
Minimize the difference in flow from emission devices.
Description
Emission uniformity means that the same amount of water is flowing from each emission
device. It is the result of good pressure uniformity and good device uniformity. It is
practically and economically impossible to design, install, and maintain a system at 100%
pressure uniformity. However, competent engineers/specialists can design a system where
the pressure at each lateral inlet will not vary beyond reasonable limits. Pressure
regulators or pressure-compensating emission devices may be required in situations
involving extreme elevation changes or long pipeline runs.
Device uniformity is critical with micro-irrigation systems because of the very small
passages which can vary due to manufacturing tolerances. Irrigation system designers
work with what is known as the “manufacturer’s coefficient of variation” which is a
measure of device uniformity as manufactured. The lower this coefficient, the more
uniform the device.