■ Site Selection for SDI Systems in
North Carolina
Subsurface drip irrigation (SDI) is a relatively new system that may give North Carolina
producers similar or higher crop yields while using less water than other irrigation systems.
Proper site selection helps ensure optimum system performance and crop yield while
minimizing expenses. This publication will help you consider the characteristics of your field,
soil, crop, cropping system, and irrigation water resources as they apply to SDI. Managerial
and farm labor resources, economic factors, and industry support infrastructure are also
discussed, as they affect your decision about the appropriateness of SDI in your situation.
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A&T State University com¬
mit themselves to positive
action to secure equal
opportunity regardless of
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two Universities welcome
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Introduction
Irrigation is commonly needed in North
Carolina despite the fact that average annual
rainfall exceeds the amount of moisture that
evaporates from fields and is used by crops,
evapotranspi ration (ET). Rain doesn’t always
fall when and where it is needed, and sandy
soils, such as those found in the coastal
plain, have a limited capacity for holding
water. To avoid potential economic loss from
under- or over-irrigation, growers need an
irrigation system that applies water uniformly
and efficiently.
To decide if SDI is the right system for
your site, you need to carefully consider
and weigh it against other alternative
systems. The water supply and pumping
considerations; soil considerations; field
size, shape, and topography; producer
preferences, practices and experiences;
crops and cropping systems; and
maintenance aspects all affect the ultimate
economic success or failure of an SDI
system on your farm. While each of the pros
and cons of a SDI system may not apply to
your situation, it is useful to recognize that
they can occur. A review of SDI advantages
and disadvantages is provided by Lamm,
State University
A&T State University
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(2002). Fail to recognize a significant
constraint or to give too much weight to a
positive aspect and you may end up with
a poorly adapted system. This publication
gives you a brief overview of the most
crucial considerations, and provides good
primary information if you are considering
SDI.
Water Supply and Pumping
Considerations
The water supply is often the limiting
factor in determining whether irrigation is
appropriate for a particular farm. How much
good quality water can your potential water
supply provide? Volume criteria include
the flow rate that can be sustained and the
reliability of the water supply, both during
a growing season and over a number of
years. A lake or pond that is filled by the
surrounding watershed should be able to
store the water needed for irrigation, but
there may not be enough rainfall to refill the
pond during the growing season. During a
dry year, you will need an additional water
source. This can be surface water from
a river or stream or groundwater from a
well. A well can supply an ample volume
of water, but the flow rate can be limited by
