Em4885 irrigation management practices to protect ground water

4 CHAPTER
Description
Depending on the soil type, newly listed or cultivated furrows may have a cloddy,
hydraulically rough surface. This Practice consists of using some type of implement to
form a slicked or unobstructed channel in furrows. Although in some soils there may be
significant subsurface compaction, the intention is to reduce surface obstructions. Slicking
the furrow will reduce the amount of erosion of small clods left by cultural practices.
Refer to IP 2.02.07 for possible beneficial effects on distribution uniformity.
IP 5.01.06 - Perform Land Grading to Optimize Furrow/Rill Gradients to Reduce
Soil Erosion
Objective
Ensure an appropriate grade for the field length and soil characteristics in order to use
surface irrigation systems efficiently without causing soil erosion.
Description
Efficient surface irrigation requires the right combination of flow, field slope, furrow/
border strip length, and soil characteristics. Too steep a gradient will cause excess
velocities in the furrow and increase potential erosion. If topsoil depth allows, make
sure that an appropriate gradient is installed.
SCS National Practices 464 and 466 address land grading and smoothing.
IP 5.01.07 - Install Tailwater Drop Structures
Objective
Reduce erosion in tailwater ditches by reducing natural gradients with the use of
control structures.
Description
Tailwater drops are applicable whenever existing land gradients result in erosive water
velocities in open ditch tailwater collection systems. Drops can be used to break an
excessively sloped tailwater ditch into a series of non-erosive grades. Or, one or more
drop structures can be placed at selected areas where there are sharp elevation changes.
A tailwater drop allows the use of a non-erosive gradient in the tailwater ditch. Drop
structures, constructed so as to be non-erosive, are installed in the tailwater ditch as
necessary to account for the terrain’s natural change in elevation.
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