Madison, Wisconsin
May 4, 2009
Source:
The American Society of
Agronomy
Crop water use efficiency (WUE, or
yield per unit of water used), also known as crop water
productivity, can be improved through irrigation management and
methods, including deficit irrigation (irrigating less than is
required for maximum yields) and supplemental irrigation
(irrigating to supplement precipitation so as to avoid crop
failure or severe yield decline). Thus, WUE is key for
agricultural production with limited water resources.
Policymakers and water resource managers working at all scales
need to evaluate the many ways in which cropping systems and the
amounts, timing, and methods of both irrigation and fertilizer
applications may be changed to improve WUE while meeting yield
and harvest quality goals. Field experiments are too costly to
address all scenarios, but computer models of crop growth and
yield may fill in the gaps if the models are shown to be
accurate predictors of WUE.
An international team of experts led by the Food and Agriculture
Organization of the United Nations developed an agronomic model
called AquaCrop to address the need for modeling of WUE under
widely varying conditions around the world and with limited
data.
To look at the ability of this and other agronomic models to
estimate WUE, a team member with the USDA Agricultural Research
Service, Bushland, Texas, organized a symposium, “Yield Response
to Water: Examination of the Role of Crop Models in Predicting
Water Use Efficiency,” at the 2007 Annual International meeting
of the Agronomy Society of America. Results using several
agronomic models were discussed.
Nine papers arising from the symposium are published in a
special section of the May–June 2009 issue of Agronomy Journal.
The papers explore how four of the simulation models were used
to simulate yield, water use, and WUE of cotton, maize (corn),
quinoa, and sunflower in North and South America, Europe, and
the Middle East. All the models simulated WUE adequately under
well-watered conditions, but tended to overestimate or
underestimate WUE under conditions of water stress. This limits
their usefulness for exploration of deficit irrigation scenarios
or rain-fed or dryland situations with less than adequate water.
According to symposium organizer Steve Evett, “Future studies
exploring WUE simulation should include evaporation or
transpiration measurements in addition to total crop water use
measurements. In doing so, management methods that reduce
evaporation in favor of transpiration can be studied and models
of WUE can be tested and improved.”
This examination of WUE estimation by multiple models helps
close the gap that exists between what can be done using crop
simulation models and what policymakers and managers need from
these models in order to develop useful management alternatives
for crop selection and timing, tillage systems, and irrigation
and fertilization practices. Development of AquaCrop and several
other models is continuing and will be guided by the findings of
these studies.
The full article is available for no charge for 30 days
following the date of this summary. View the abstract at
http://agron.scijournals.org/cgi/content/abstract/101/3/423.
A peer-reviewed international journal of agriculture and
natural resource sciences, Agronomy Journal is published six
times a year by the American Society of Agronomy, with articles
relating to original research in soil science, crop science,
agroclimatology and agronomic modeling, production agriculture,
and software. For more information visit:
http://agron.scijournals.org.
The American Society of
Agronomy (ASA) is a scientific society helping its 8,000+
members advance the disciplines and practices of agronomy by
supporting professional growth and science policy initiatives,
and by providing quality, research-based publications and a
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