Freddie Lamm, Todd Trooien, Gary
Clark, Dan Rogers, Mahbub Alam
Kansas State University
Subsurface drip irrigation (SDI) and electrotechnologies are
excellent partners as each complement the other. This paper will conceptually describe
some of the potential interrelationships. The scope, magnitude, and significance of these
interrelationships is subject to a host of variables, such as climate, soils, crops,
irrigation management, economics of alternative energy sources, and availability of
REDUCED ENERGY REQUIREMENTS WITH SDI
Large amounts of energy are used for irrigation. Slogett
(1985) reported that 50% of the energy used for irrigation in the US in 1983 was used in
the Southern and Northern Plains. SDI can reduce energy use through reduced operating
pressures, lower water use, and improved fertilizer and herbicide utilization.
SDI systems can be operated at lower pressures than medium to
high pressure center pivot sprinkler systems and have comparable pressures to low pressure
center pivot sprinkler systems. However, SDI systems will generally have a higher
operating pressure than gravity or surface irrigation systems.
Energy requirements can also be reduced through decreased
irrigation water use. Various estimates in the literature report that SDI can reduce
irrigation water use by 25 to 50% of sprinkler and surface irrigation requirements. Water
use reductions can be accomplished with SDI by eliminating or greatly reducing
evaporation, runoff and drainage. In addition, SDI can reduce water applications by just
meeting and not exceeding plant water needs through more precise and timely small
applications of water. The amount of effective precipitation can also be increased with
SDI because the soil surface and interrow areas are drier and more receptive to
The manufacturing of chemical fertilizers requires large
amounts of energy, thus improved fertilizer utilization through spoon feeding the crop
with SDI can also save energy. In addition, SDI can potentially result in reduced weed
control problems and thus require less herbicides.
SDI AND AUTOMATION FOR MONITORING AND CONTROL
As farming operations increase in size and become more
integrated to make use of the economic advantages of such operations (CAST, 1996; NRC,
1996), labor savings through automation become increasingly important. SDI is an
irrigation method that is not only well-suited to automation, but is also a method that
can utilize automation to achieve high standards of water conservation and water quality
Automation is also required (or desirable) for SDI for the
high frequency and precise water and fertilizer capabilities of the system. Automation is
also useful for other irrigation and cultural practices, such as chemigation, computer and
sensor-aided irrigation scheduling, and pest management.
Automation is more convenient with electrical pumping plants
and typically requires electrical monitoring and control systems. Automated systems are
also relatively easy to adapt to electrical load management and off-peak power programs.
Frequent starting and stopping of the irrigation cycle is more easily accommodated with
electric motors and controls as compared to internal combustion engines.
SDI AND LOAD MANAGEMENT
SDI systems can uniformly apply and distribute very small
irrigation amounts (< 0.05 inches) for each event as compared to center pivot sprinkler
and surface irrigation systems. As a result, SDI systems are well-suited for frequent or
intermittent interruption of irrigation service as might be required by electrical load
Greater design irrigation capacities are typically associated
with SDI systems because higher emitter flow rates are usually required to prevent emitter
plugging. Higher irrigation capacities allow for more intermittent irrigation events.
Lower irrigation capacities can be designed for SDI systems through dividing the system
into more zones, but this increases the investment cost for the system. As a counterpoint
to the typical higher irrigation capacities, there is some evidence that a multi-zoned,
high frequency SDI system may be utilized in a deficit irrigation mode for field corn to
either conserve irrigation water or to increase irrigated acres.
SDI AND SCALE FACTORS
The economics of various size SDI systems are more
proportionally adjustable than center pivot sprinklers systems (O'Brien, et al. 1997). As
a result, SDI systems can be utilized on smaller irrigated areas and irregularly shaped
fields and thus require smaller irrigation pumping plants. On smaller irrigation systems a
wider range of continuous duty electric motors are available for pumping than internal
combustion engines. In some cases, the smaller SDI systems could use single phase electric
Small SDI irrigation systems that can also tolerate
interrupted irrigation cycles could be good candidates for alternative electrical
generation schemes such as wind or solar energy.
The use of electrotechnologies with SDI, though not
absolutely required, is an excellent combination which can enhance the efficiency and
environmental friendliness of irrigation. Similarly, SDI can be a excellent partner to
electrotechnologies by reducing and balancing energy loads and also by being a
well-managed and predictable load.
The Hugoton natural gas fields in southwest Kansas, formerly
one of the world's largest gas reserves, is being rapidly depleted and is nearing the end
of its useful commercial life. As this happens along with the further deregulation of
natural gas, irrigators in much of the Great Plains region will be scrambling to find
alternative energy sources. Electrical power stands to pick up a sizeable share of this
CAST (Council for Agricultural Science and Technology). 1996.
Future of irrigated agriculture. Task Force Report 127. CAST, Ames IA. 76 pp.
NRC (National Research Council). 1996. A new era for
irrigation. National Academy Press, Washington DC. 203 pp.
O'Brien, D., Rogers, D., Lamm, F. and G. Clark. 1997.
Irrigation system economics as affected by field size. 1997 Central Plains Irrigation
Short Course and Equipment Exposition Proceedings, Colby, Kansas, February 4. pp. 81-93.
Slogett, G. 1985. Energy and US agriculture: Irrigation
pumping, 1974-1983. USDA, Agriculture Economic Report No. 545. This paper was first
presented at the EPRI-Agricultural Technology Alliance semi-annual meeting, Boise, Idaho,
May 28-30, 1997.
The corresponding author is:
Dr. Freddie Lamm
Research Agricultural Engineer
KSU Northwest Research-Extension Center
105 Experiment Farm Road Colby, Kansas 67701-1697
Phone: 785-462-6281 Note: