WSPC00105

• File Number: 8029
• Description: Section D General Correspondence-Colorado Agencies-Alpha not Basin Related
• State: CO
• Date: 12/1/1991
• Author: CWRRI
• Title: CWRRI-Colorado Water Newsletter
• Water Supply Pro - Doc Type: Publication

002569

FEATURES

13

NITROGEN AND WATER MANAGEMENT USING AN EXPERT SYSTEM
by
Paul D, Ayers, IsrtuI Broner, Jim C, Loftis and Uoyd R, Walker
Extension Agricultural Engineers

"Expen systems" are software packages that simulate human
decision-making, Such systems are now being developed for
many applications in agriculture, A barley management expen
system has been developed by the Deparunent of Agricultural
and Chemical Engineering in cooperation with the College of
Agricultural Sciences and the Coors Brewing Company, The
barley management expen system is designed to produce water
and fenilizer recommendations to maximize yield (subject to
the strict quality requirements of the Coors Brewing
Company).

The expen system makes recommendations using a
combination of arithmetic calculations. such as crop
consumptive use and soil water balance calculations. and rules,
such as proper timing of fertilizer application, The set of rules
used in the system was developed through extensive
questionnaire interviews of barley production experts, If it
performed correctly, such a system could be used by barley
producers to obtain recommendations similar to those provided
by Coors own agronomists without the need for actual visits
and consultations by those expens,

During the 1990,91 growing seasons, the barley expen system
was tested and verified wtder field conditions at Center,
Colorado, and Burley, Idaho, The tests included a comparison
of recommendations given by a human expen and the
recommendations of the expen system, Plots using each set of
recommendations are produced; and yields, along with water
and fertilizer inputs. are compared to determine which set of

recommendations results in better crop performance. The test
results from the two locations are shown in the table below,
At both locations. the human expen recommended higher
applications of nitrogen, Since both locations have light.
shaIlow soils, over.irrigation leaches fenilizer below the rOOt
zone. Consequently. a common practice is recommending
higher applications of nitrogen to be "on the safe side" and
compensate for leaching, This is economically attractive. even
for a very small yield increase. since the cost of fertilizer is
low, However, the field trials reveal that nearly the same yield
and net return can be obtained by applying approximately one-
haIf of the normal application of nitrogen,

Although there was a small penalty in net returns from using
the expen system recommendations, there were two important
benefits, First the brewing qnalities of the barley were
improved in terms of protein content, (Lower protein is better
for beer,) In some cases a bener price per bushel for high
quality barley may offset slightly lower yields, The second
advantage. greatly reduced potential for nitrate contamination
of growtdwater. may become extremely important as
environmental concerns and regulations increase.

Overall, the expen system performed very well compared to its
human cowtterpart, This study provides another piece in the
growing list of evidence that such software can be a valuable
tool for helping fanners manage crop production systems at the
high level required to maintain farm profitability and
envirorunental quality,

Applied No,of Yield Protein Yield Net
nitrogen irriga- content price return
(lb/a) tions bula % $/100 Ib $/a
Center, Colorado
Human 120 20 155 13,2 7,14 510
expen
Expen 60 18 132 12,0 7,39 461
system
Burley. Idaho
Human 110 6 99 11.6 7,54 344
expen
Expert 68 5 92 10,8 7,59 338
system

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