Em4885 irrigation management practices to protect ground water

4 CHAPTER
IP 2.02.09 - Rip Hardpans and Compacted Soil Layers to Improve Infiltration Rates
Objective
Increase infiltration rates and lower erosion.
Description
Soil texture and structure partially govern infiltration rates. Fields with very low
infiltration rates can be hard to irrigate efficiently as excessive surface runoff may
be generated. Ripping, chiseling, or some other form of subsoiling can improve
infiltration rates. This can reduce erosion and help in increasing overall
application efficiency.
IMPORTANT!!! Note that increased infiltration rates will increase the likelihood of deep
percolation. The grower must maintain control of the total water application at all times.
SCS National Practice 324 addresses chiseling and subsoiling to improve infiltration rates.
IP 2.02.10 - Use Cutback Furrow Flows to Reduce Surface Runoff
Objective
Reduce the amount of surface runoff during a furrow irrigation.
Description
Correct operation of furrow/rill irrigation systems entails:
1. Wetting the furrow in an appropriately short time period
2. Then allowing water to run in the fully wet furrow until sufficient water
has infiltrated at all points along the furrow.
Regardless of the amount of time taken to wet a furrow, once it is fully wet runoff
commences and must be managed. IP 2.02.11 discusses the installation of runoff reuse
systems as one form of management. An optional Practice is a “cutback” furrow flow.
A cutback furrow flow occurs when the average furrow flow is reduced some time after
the entire furrow is wetted. This reduced furrow flow will result in reduced surface runoff.
For example, the initial furrow flow may be 8 gallons per minute (GPM) so as to wet the
furrow in an acceptably short time period. The large initial flow may then be reduced to
4 GPM once significant runoff starts.
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