Em4885 irrigation management practices to protect ground water

4 CHAPTER
Efficient, Effective Irrigations
The goal is efficient, effective irrigations. Efficient irrigations make the best use of available
water resources while minimizing negative impacts to water quality due to surface/sub-surface
losses. Effective irrigations help do what is intended—produce a profitable crop. Efficient, effective
irrigations are the result of knowing when, how much, and how to irrigate.
When to irrigate is an agronomic decision. Timing of irrigations should enhance the total
cultural system. Commonly, irrigations are timed to avoid stress due to lack of soil water. In some
cases, desired crop development will dictate some stress. In other situations, irrigations may be
timed to aid fertilizer applications.
In any situation, the irrigator must also know how much to irrigate. Normally this is:
1. the amount of water required to refill the effective root zone of the plant,
2. plus required leaching for salt control,
3. plus unavoidable losses to deep percolation, surface runoff, or immediate evaporation.
Improving knowledge of how much to irrigate will involve some form of irrigation scheduling
as discussed in Practice 2.01.05.
The irrigator must know how to irrigate so as to minimize unavoidable losses to immediate
evaporation, deep percolation, and surface runoff. Note that it will be impossible to irrigate without
some losses unless parts of the field are underwatered.
How to irrigate does not refer to the mechanics of setting up a booster pump or laying out
sprinkler pipe. It refers to the ability to achieve good distribution uniformity while maintaining
control over the total application. Controlling the total amount of water applied requires:
1. Water applications to be measured (IP 2.01.01).
2. Sufficient control to be present in the irrigation system, including hardware, labor to
operate it when needed, and management to tell labor when to stop an irrigation
(planning, IP 2.01.06).
3. Sufficient flexibility to be in the primary water supply (deep well, river/stream pump,
or irrigation district turnout) so that the grower can turn the water on and off when needed.
Presentations of the Implementation Practices
The Practices for this Objective are presented in four sections. The first section presents
Practices that are applicable to any irrigation system type. The other three sections pertain to
specific irrigation system types. Section 2 is for furrow/rill systems, section 3 is for sprinkle
systems, and section 4 is for micro-irrigation systems.
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