Application Efficiency in Irrigation
Key Points
• Major water loss pathways,
during or shortly after irrigation,
include percolation or drainage
from the root zone, evaporation
from soil and plant surfaces, and
runoff from the target site.
• Water application efficiency may
be improved by regular
equipment maintenance, proper
irrigation scheduling and residue
management.
As readily available water resources become limited in some areas, emphasis should be placed on
efficient use of irrigation water for maximum economic return and the sustainability of water
resources. Water application efficiency (WAE) provides a general sense of how well an irrigation
system performs to get water to plant roots. Specifically, WAE measures the portion of the total water
volume delivered to the field that is stored in the root zone that is available to meet crop
evapotranspiration (ET) needs.
Water Loss Mechanisms
Application efficiency is influenced by any mechanism which results in applied water being unavailable
for plant use. The water is not really “lost”, but does not reach plant roots. Generally, the major water
loss pathways, during or shortly after irrigation are percolation or drainage from the root zone,
evaporation from soil and plant surfaces, and runoff from the target site.1 Depending on the irrigation
system, additional water losses can occur from small droplet evaporation into the air, droplet drift, and
leaks from sprinkler or drip pipelines.
Improving Application Efficiency
Equipment Maintenance. Irrigation systems should be periodically inspected and properly
maintained. Also, application uniformity should be measured. For example, a detached or
malfunctioning sprinkler nozzle could lead to over-irrigation, resulting in excessive runoff and
percolation below the root zone or dry patches in the field.2 A malfunctioning nozzle in the outermost
portion of a pivot system will impact a much greater portion of the field compared to a nozzle located
near the center. Even a minor system problem can cause significant yield reduction. Inconsistent
water application may lead to a corn yield decrease of 20-40 bu/acre and significant economic
losses.3 Always refer to the manufacturer’s manual before performing any irrigation maintenance.
• Strategies to improve application
efficiencies vary among irrigation
systems.
Frequency of Irrigations. With some types of spray irrigation equipment, application efficiency can be reduced as application frequency increases. With
every application, a percentage of the water applied will evaporate from the wet soil and plant surface. The evaporation rate from the crop canopy is
influenced by the climate (humidity and temperature), time available for evaporation to occur, and the surface area of the droplets. Net canopy evaporation
is considered the greatest evaporative loss from most sprinkler or spray technologies.1 Following a 1-inch application, researchers in Texas observed a 3%
evaporative loss (0.03 inches) from the plant canopy with a spray head sprinkler and an 8% loss (0.08 inches) with a low-angle impact sprinkler.4 The total
seasonal canopy evaporative loss may be increased when the canopy is frequently wetted and allowed to evaporate between applications as opposed to
applying the same amount of water in fewer applications. Also, avoid irrigating bare soil to minimize evaporation loss. Percolation losses may increase with larger less frequent irrigations. However, these potential losses can be
minimized by scheduling irrigations based on soil moisture measurements or estimates. Soil moisture levels can
be monitored with soil sensors and/or weather-based crop ET estimates to determine when and how much
irrigation is needed. Optimum irrigation scheduling (frequency and amount) can improve the overall efficiency of
water use.
Residue Management. Conservation tillage practices such as no-till and strip-till have shown to improve soil
water holding capacity, water infiltration rates, soil moisture retention, and reduce runoff compared to
conventional tillage systems.1
Irrigation Systems
Sprinkler Irrigation Systems. Potential losses include droplets drifting to unintended areas due to wind and evaporation of droplets from the air, crop
canopy, and soil surface. Substantial losses from wind drift and/or droplet evaporation can occur if the sprinkler design or pressure produces a high
Application Efficiency in Irrigation
percentage of very fine or small diameter droplets.1 Additionally, water that reaches the soil surface can be lost from runoff and percolation below the root
zone. Drift and evaporation losses can be reduced with the use of lower-pressure systems that produce larger droplet sizes and by applying irrigation when
temperatures and wind speeds are low. Evaporation from plant surfaces can be minimized as spray heads are moved closer to the soil surface, resulting in
less wetting of the crop canopy.
Low-pressure adaptations to traditional sprinkler systems include: LESA (low elevation, spray application), MESA (medium elevation, spray application),
LPIC (low pressure, in-canopy), and LEPA (low energy, precision application). Water runoff can be an issue with these systems if application rates are not
matched to soil intake rates. Cultural practices such as furrow diking can help minimize losses due to runoff.
Irrigation Furrows. Furrow irrigation has one of the lowest application efficiencies among irrigation methods (Table 1). Potential water losses during
furrow irrigation may include: evaporation of water in the furrow, runoff, evaporation from the soil surface, and percolation below the root zone. With
surface irrigation, it is important to irrigate the entire field as quickly as possible. Furrows that are too long may result in deep percolation at the upstream
end of the furrow by the time the downstream end is adequately watered.
Strategies for improving furrow application efficiency include: recovery and reuse of runoff water (tailwater), irrigating every other furrow, and surge
irrigation. With surge irrigation, a surge valve is used to alternately send pulses of water down the furrow during advance cycles. Alternating wetting and
drying allows soil particles in the bottom of the furrow to settle and may reduce the intake rate of the soil, which may help water advance down the furrow
faster. Once water reaches the end of the furrow, pulses of water are sent down the furrow during soak cycles. Microirrigation Systems. Microirrigation systems, such as surface and
subsurface drip, are low-pressure systems with the potential to deliver water at
very high efficiencies if properly designed, maintained, and managed. These
systems tend to have the highest initial investment costs and management
requirements compared to other types of irrigation, but can also have the highest
application efficiencies and crop water productivity, especially when water is
limited. Drip systems should be inspected regularly for the best performance.
Water filtration is extremely important to the long-term viability of microirrigation
systems, otherwise emitter clogging can occur within a few years. Sources
1Howell,
T.A. and Evett, S.R. 2005. Pathways to effective applications. Proceedings of the 2005 Central
Plains Irrigation Conference, Sterling, Colorado. https://www.ksre.ksu.edu/ 2Irmak, S., Odhiambo, L., Kranz, W.L., and Eisenhauer, D.E. 2011. Irrigation efficiency and uniformity,
and crop water use efficiency. Publication EC732. University of Nebraska-Lincoln Extension.
http://extensionpublications.unl.edu 3Burr, C., Martin, D., Kranz, B., and Zoubek, G. 2013. Regular pivot maintenance can help ensure
application efficiency. CropWatch. University of Nebraska-Lincoln. http://cropwatch.unl.edu/archive//asset_publisher/VHeSpfv0Agju/content/checklist-for-maintaining-your-pivot-unl-cropwatch-march-142013. 4Yonts, C.D., Kranz, W.L., and Martin, D.L. 2007. Water loss from above-canopy and in-canopy
sprinklers. NebGuide G1328. University of Nebraska-Lincoln Extension. http://extensionpublications.unl.edu/ 5Broner, I. 2005. Irrigation scheduling. Fact sheet 4.708. Colorado State University Extension.
http://extension.colostate.edu/topic-areas/agriculture/irrigation-scheduling-4-708/ 6Irrigation handbook for the Great Plains. 2014. Monsanto Water Utilization Learning Center.
141110125054. http://www.monsanto.com/. Web sources verified 01/14/16. 150315145842 Table 1. Potential Application Efficiencies for Well-Designed and Well-Managed Irrigation Systems.
Irrigation System
Potential
Application
Efficiency (%)
Sprinkler Irrigation
Systems
Surface Irrigation
Systems
Microirrigation Systems
LEPA
80-90
Linear move
75-85
Center pivot
75-85
Traveling gun
65-75
Furrow
(conventional)
45-65
Furrow (surge)
55-75
Furrow
(with tailwater
reuse)
60-80
Microspray
85-90
Subsurface drip
>95
Surface drip
85-95
Table modified from Irmak, S., Odhiambo, L., and
Eisenhauer, D.E. 2011. Irrigation efficiency and uniformity,
and crop water use efficiency . Publication EC732.
University of Nebraska-Lincoln Extension.
Individual results may vary, and performance may vary from location to location and from year to year. This result may not be an indicator of
results you may obtain as local growing, soil and weather conditions may vary. Growers should evaluate data from multiple locations and years
whenever possible. ALWAYS READ AND FOLLOW PESTICIDE LABEL DIRECTIONS. Channel® and the Arrow Design® and
Seedsmanship At Work® are registered trademarks of Channel Bio, LLC. All other trademarks are the property of their respective owners.
©2016 Monsanto Company. 150315145842 012716DLB